7
Non-Engine Technologies

INTRODUCTION

This chapter focuses on reducing fuel consumption with non-power-train technologies. These technologies affect engine performance either directly or indirectly in a manner that reduces fuel consumption. For example, a significant portion of this chapter discusses the state of readiness, cost, and impact of reducing vehicle mass. Reducing mass reduces the energy necessary to move a vehicle, and thus reduces fuel consumption. The complexity of substituting advanced, lightweight materials affects the redesign of a part or a subsystem, component manufacturing (including tooling and production costs), and joining, and raises interface issues that mixing different materials can pose. The term material substitution oversimplifies the complexity of introducing advanced materials, because seldom does one part change without changing others around it. Advanced lightweight materials show great promise for reducing mass throughout a vehicle’s body structure and interior. Low-rolling-resistance tires and reduction of aerodynamic drag are also discussed as technologies that can lower tractive force and result in reduced fuel consumption. Improvements in energy-drawing devices such as air conditioner compressors and power steering can reduce fuel consumption either by electrification or by improving their efficiency. New transmissions with more gears or that are continuously variable improve power train efficiency. All these options either reduce the demand for power from the engine or enable operating the engine at a more efficient point to reduce fuel consumption.

NON-ENGINE TECHNOLOGIES CONSIDERED IN THIS STUDY

The committee considers car body design (aerodynamics and mass), vehicle interior materials (mass), tires, vehicle accessories (power steering and heating, ventilation, and air conditioning [HVAC] systems), and transmissions as areas of significant opportunity for achieving near-term, cost-effective reductions in fuel consumption. These will be considered in some detail below.

Aerodynamics

As discussed in Chapter 2, the force required to overcome drag is represented by the product of the drag coefficient, the frontal area, and the square of speed. The actual formula is F = ½ Cd AV2 where A is the vehicle frontal area, V is velocity, and Cd is the drag coefficient. Cd typically ranges from about 0.25 to 0.38 on production vehicles and depends on several factors with the primary influence coming from vehicle shape and smaller influences from other factors, such as external mirrors, rear spoilers, frontal inlet areas, wheel well covers, and the vehicle underside. Vehicles with higher Cd values (greater than .30) may be able to reduce the Cd by up to 10 percent at low cost without affecting the vehicle’s interior volume. In trying to reduce fuel consumption, certain vehicles achieved very low drag coefficients, for example, GM’s EV1 had a Cd of 0.19, and the third-generation Prius has a Cd of 0.25.1 In the committee’s judgment a Cd of less than 0.25 would require significant changes that could include the elimination of outside rear view mirrors, total enclosure of the car underbody, and other modifications that may be very costly. Vehicles that exist today with a low Cd (below 0.25) are usually specialty vehicles (e.g., sports cars and high-mileage vehicles like the Prius). The 2010 Mercedes E-class is the only production vehicle with a Cd as low as 0.25. However, this is a luxury-class vehicle and retails for $50,000 (or more). Some costs are incurred from incorporating aerodynamic features such as the integrated front spoiler, an option that may not be possible for lower-cost vehicle classes. Further reducing Cd for lower-cost vehicles is expensive and perhaps beyond a point of diminishing returns. Vehicles with higher Cd (e.g., trucks,



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7 Non-Engine Technologies INTRODUCTION cost-effective reductions in fuel consumption. These will be considered in some detail below. This chapter focuses on reducing fuel consumption with non-power-train technologies. These technologies affect Aerodynamics engine performance either directly or indirectly in a manner that reduces fuel consumption. For example, a significant As discussed in Chapter 2, the force required to overcome portion of this chapter discusses the state of readiness, drag is represented by the product of the drag coefficient, cost, and impact of reducing vehicle mass. Reducing mass the frontal area, and the square of speed. The actual formula reduces the energy necessary to move a vehicle, and thus is F = ½ Cd AV2 where A is the vehicle frontal area, V is reduces fuel consumption. The complexity of substituting velocity, and Cd is the drag coefficient. Cd typically ranges advanced, lightweight materials affects the redesign of a from about 0.25 to 0.38 on production vehicles and depends part or a subsystem, component manufacturing (includ- on several factors with the primary influence coming from ing tooling and production costs), and joining, and raises vehicle shape and smaller influences from other factors, such interface issues that mixing different materials can pose. as external mirrors, rear spoilers, frontal inlet areas, wheel The term material substitution oversimplifies the com- well covers, and the vehicle underside. Vehicles with higher plexity of introducing advanced materials, because seldom Cd values (greater than .30) may be able to reduce the Cd by does one part change without changing others around it. up to 10 percent at low cost without affecting the vehicle’s Advanced lightweight materials show great promise for interior volume. In trying to reduce fuel consumption, certain reducing mass throughout a vehicle’s body structure and vehicles achieved very low drag coefficients, for example, i nterior. Low-rolling-resistance tires and reduction of GM’s EV1 had a Cd of 0.19, and the third-generation Prius aerodynamic drag are also discussed as technologies that has a Cd of 0.25.1 In the committee’s judgment a Cd of can lower tractive force and result in reduced fuel consump- less than 0.25 would require significant changes that could tion. Improvements in energy-drawing devices such as air include the elimination of outside rear view mirrors, total conditioner compressors and power steering can reduce fuel enclosure of the car underbody, and other modifications consumption either by electrification or by improving their that may be very costly. Vehicles that exist today with a efficiency. New transmissions with more gears or that are low Cd (below 0.25) are usually specialty vehicles (e.g., continuously variable improve power train efficiency. All sports cars and high-mileage vehicles like the Prius). The these options either reduce the demand for power from the 2010 Mercedes E-class is the only production vehicle with engine or enable operating the engine at a more efficient a Cd as low as 0.25. However, this is a luxury-class vehicle point to reduce fuel consumption. and retails for $50,000 (or more). Some costs are incurred from incorporating aerodynamic features such as the inte- NON-ENGINE TECHNOLOGIES CONSIDERED IN THIS grated front spoiler, an option that may not be possible for STUDY lower-cost vehicle classes. Further reducing Cd for lower- cost vehicles is expensive and perhaps beyond a point of The committee considers car body design (aerodynamics diminishing returns. Vehicles with higher Cd (e.g., trucks, and mass), vehicle interior materials (mass), tires, vehicle accessories (power steering and heating, ventilation, and 1 See http://www.greencar.com/articles/20-truths-gm-ev1-electric-car. air conditioning [HVAC] systems), and transmissions as php and http://pressroom.toyota.com/pr/tms/toyota/all-new-prius-reveal. areas of significant opportunity for achieving near-term, aspx, respectively. 99

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100 ASSESSMENT OF FUEL ECONOMY TECHNOLOGIES FOR LIGHT-DUTY VEHICLES vans, and box-like vehicles such as the Scion and Flex) can example, for some non-structural applications, steel becomes reduce Cd, although vehicle functionality is diminished. If cost competitive vis-à-vis plastic at around 50,000 units. the functionality is compromised, then the vehicle’s appeal Two key strategies for achieving mass reduction are to the consumer would be reduced. changing the design to require less material, or substituting As noted above, the aerodynamic drag is the product of lighter-weight materials for heavier materials. Assuming that the drag coefficient Cd, the vehicle frontal area, and speed. the car size is essentially fixed, there are design techniques Reduction in the frontal area, reducing vehicle size, and that can reduce mass. Several different body architectures are lower speed limits would also improve fuel consumption; described below. Material substitution relies on replacing a however, exploring these options is outside the committee’s heavier material with a lighter one while maintaining per- statement of task. formance (safety and stiffness). For example, high-strength steel can be substituted for mild steel (and therefore a thinner gauge can be used), aluminum can be substituted for steel, Car Body Design and Interiors plastic can be substituted for aluminum, and magnesium can Optimized car body design focuses on a balance between be substituted for aluminum. It is often a misnomer to refer structural stiffness, noise/vibration/harshness (NVH), safety to this as material substitution. The part (or subsystem) often (crashworthiness), comfort (space), and mass. Today’s pri- has to be redesigned, and the fabrication process may change ority of reducing fuel consumption places an emphasis on and the assembly process may be different. In fact, the mate- mass reduction, with the assumption that other performance rial cost differential may be insignificant relative to the costs criteria will not be unduly compromised. Vehicle mass can associated with the changes in fabrication and assembly. be reduced without compromising size, crashworthiness, and NVH, although countermeasures are often required to Body Design and Material Selection restore NVH performance when mass is reduced. The majority of vehicle mass can be attributed to the body The great majority of vehicles produced today are uni- structure, closure panels (doors, hood, and deck lid), interior body design. The unibody design is a construction technique seating and trim components, glass, power train components that uses the internal parts as the principal load-bearing (engine, transmission, etc.), and the chassis (axles, wheels, structure. While the closure panels (doors, hood, and deck brakes, suspension, etc.). Steel, cast iron, fiber/reinforced lid) provide important structural integrity to the body of the composites, glass, and aluminum have been the dominant vehicle, the outer skin panels, defined as the metal outer materials for these components, with steel accounting for panels on the entire automobile that are painted and vis- the majority of mass. Estimates for the amount of these ible to the consumer, do not. This design has replaced the materials in today’s average, high-volume vehicles are listed traditional body-on-frame design primarily because it is a in Table 7.1 (Carpenter, 2008). The typical baseline vehicle lighter. Body-on-frame designs, where an independent body used for comparison is described as a 3,600-lb model-year structure (with its own structural integrity) sits on top of a 2009 comparable to a Toyota Camry or Chevrolet Malibu. separate frame (with its own structural integrity), still prevail High-volume vehicle manufacturing is generally associ- on some heavier vehicles such as pickup trucks and larger ated with the production of more than about 100,000 vehicles SUVs because of its overall superior strength and stiffness. per year (although some might say 50,000). Low volume Another design, the space frame, was recently developed might be under 25,000 vehicles per year. This is important to accommodate aluminum. The forming and joining of because different materials become cost competitive at aluminum cannot easily or cheaply be replicated in a steel different volumes. Higher-cost materials (composites, alu- unibody design. A typical space frame is composed of ex- minum, and magnesium) become more cost competitive at truded metal connected at the ends, which are referred to as lower volumes because the forming tools in most cases have nodes. Both the unibody and the space frame have “hang-on” a lower investment cost offsetting the higher material cost. panels where the skin panels have little to no structural load. Steel requires high-cost forming tools but has a lower mate- A final design architecture, the monocoque, relies on the rials cost, making steel competitive at higher volumes. For outer skin surface as a principal load-bearing surface. The TABLE 7.1 Distribution of Materials in Typical Vehicle (e.g., Toyota Camry and Chevrolet Malibu) Approximate Content in Cars Material Comments Today, by Weight (percent) Iron and mild steel Under 480 Mpa 55 ≥ 480 Mpa (in body structure) High-strength steel 15 Aluminum No aluminum closure panels; aluminum engine block and head and wheels 10 Plastic Miscellaneous parts, mostly interior trim, light lenses, facia, instrument panel 10 Other (magnesium, titanium, rubber, etc.) Miscellaneous parts 10

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101 NON-ENGINE TECHNOLOGIES monocoque is seen in very low volumes because there are hydro-formed sheet metal. The use of tubes and laser few applications where it is structurally and economically blanks can make more optimal use of metal (steel or viable. Generally, these three designs are associated with the aluminum) and result in less mass in the structure following materials: without compromising design criteria. These methods may increase or decrease costs depending on the • Unibody—steel-based structure (mostly steel stamp- application. ings) usually with steel skin panels but sometimes plastic or aluminum skin panels. This design has high Most steel and mixed-material vehicles (e.g., steel and investment (engineering and tooling) costs and is de- aluminum) today are unibody, and aluminum-intensive signed for high volume. vehicles tend to be space frame designs, but these are low • Space frame—usually an aluminum-based structure volume due to cost. The unibody design was developed (aluminum castings, extrusions, and sheet). This design primarily for steel, and the conventional vehicle today is is less complex than the unibody and has lower invest- composed of about 65 percent steel (both mild and high ment costs, which are typically offset by higher material strength). Various components of a unibody can have alter- costs. Because of the high material costs (that are vari- native lightweight materials, including high-strength steel, able with volume), this is typically a low-volume design. polymers/composites, and aluminum directly substituted on • Monocoque—reinforced resin/composite body struc- a part-by-part basis to help reduce mass on a limited basis. ture using the skin to bear loads. Today, this architec- Sheet molding compound (SMC plastic) body panels are ture is uncommon for passenger automobiles and more sometimes used for fenders or exterior closure panels to common for aircraft or ships. save weight, and in the case of low-volume vehicles, to save costs. The ability to substitute alternative materials, however, The space frame and monocoque structures are associ- can be limited because of forming (part shape), joining, and ated today with niche vehicle markets, whereas the unibody interface issues between mixed materials. Steel unibody with its steel-based structure is common (perhaps found in designs can accommodate polymer/composite or aluminum more than 99 percent of today’s automobiles). These design closure panels because these parts can be easily isolated from approaches differ from the body-on-frame design that is the remainder of the structure since they are fastened onto the well suited for heavier “working” vehicles like trucks and structure. Many unibody steel-based vehicles made in North SUVs. Body-on-frame readily achieves all the desired design America have aluminum hoods and deck lids, but steel doors. criteria, except that it is heavy because of the large frame Hoods and deck lids are simpler designs than doors (they are components. flatter and have fewer parts, and therefore are less expensive and less complex to switch over to aluminum). Steel doors could also be converted to aluminum in many cases, as is Reducing Mass Using Alternative Materials often done in Europe, but in North America their size and There are several methods to make steel structures lighter, geometry would make this conversion relatively expensive. regardless of their design construction: The mass savings by introducing high-strength steel re- sults from the ability to down-gauge the thickness over mild • Substitute higher-strength steel for lower-strength steel while maintaining the same strength as the thicker steel. Higher-strength steel can be down-gauged (made mild steel part. Down-gauging reduces stiffness, and so this thinner). There are, however, forming and joining is not a solution in some cases where stiffness is important. issues with higher-strength steel that limit where it can Also, as the strength of steel increases, its ability to be be applied, and down-gauging can reduce the ability to formed into different shapes is reduced (its allowable percent meet stiffness criteria. elongation is reduced). This reduced formability also limits • Substitute sandwich metal material for conventional where high-strength steel can be applied. The outside panels steel. Sandwich material has layers of steel or alumi- (skin panels) on a unibody are predominantly non-structural num (usually three), often with the internal layer in and subject to dents, thus also limiting the ability to down- the form of honeycomb or foam. Other layered mate- gauge these panels. The tools that form high-strength steel rials can include bonded steel with plastic/polymers. parts cost more, require greater maintenance because they This cladding material can achieve high stiffness and are subject to wear, and require greater forming pressures strength levels with low mass. Sandwich material is in production. In most cases, high-strength steel parts cost light, is very stiff, and can be formed for many parts. more than comparable mild steel parts. New, advanced high- On the downside, joining it to other parts can be diffi- strength steels are being developed to give high-strength cult, its availability is limited today, and it is expensive steel greater formability and weldability. These advanced to produce. high-strength steels, expected to be available within a few • Introduce new steel designs that are available, such as years, can reduce mass on some compatible parts by around with laser welded blanks and hydro-formed tubes or 35 percent. This is achieved by using high-strength steel to

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102 ASSESSMENT OF FUEL ECONOMY TECHNOLOGIES FOR LIGHT-DUTY VEHICLES reduce part thickness by 35 percent (e.g., replacing 1.8-mm- greater supply of the base material of PMC. One expert stated thick mild steel with 1.2-mm-thick high-strength steel). that carbon fiber will see wider use in the future, but primar- Factors such as part geometry and subsystem stiffness can ily on lower-volume (fewer than 100,000 vehicles per year), limit viable applications of high-strength steel or constrain higher-performance vehicles (Carpenter, 2008). the reduction in thickness. The cost differential (by pound) varies significantly for An aggressive approach to introducing aluminum into alternative materials. High-strength steel might cost double the structure may dictate a totally different body design the price of mild steel ($0.80 versus $0.40 per pound), and approach, such as shifting from a unibody to a space frame aluminum might cost four or five times that of steel (per structure. The space frame design has been developed pound). Other materials such as magnesium and titanium are recently for aluminum-intensive structures. The structure also expensive and have volatile price fluctuations. is composed of aluminum castings, extrusions, and sheet. It is important to recognize that the comparison of differ- This design is lighter than a comparable steel design and ent materials is complicated by many factors, making a cost is in production today, but is used only on lower-volume, analysis difficult. Tooling costs and parts fabrication costs higher-end vehicles because of its high cost. Introducing an differ significantly for different materials. aluminum-intensive structure would necessitate a complete vehicle redesign, requiring several years at extremely high • The amount of material (pounds) needed by the light- development costs (see the product development process weight material is different from the incumbent material. discussion in the section “Timing Considerations for Intro- • Because of part fabrication, the optimal design with ducing New Technologies” below in this chapter). the lightweight material may be very different from Polymer-matrix composites (PMCs) are beginning to the design of the original part. For example, some be introduced into higher-volume vehicles. Viable options steel parts cannot be formed exactly the same out of for PMC are for it to be reinforced with glass fibers, natu- aluminum because of formability constraints. Also, ral fibers, or carbon fiber to give it strength. Glass- and if you substitute a material that is cast (magnesium) natural-fiber-reinforced PMCs are lower cost than carbon instead of stamped (steel), the forming cost and the fiber, but they have less strength. Since they incur lower cost, part design are different. it is likely that these applications will be seen on higher- • The tooling to form the alternative material is likely to volume vehicles before there is significant use of carbon fiber be different than the tooling for the incumbent mate- composites. Carbon fiber is a promising lightweight material rial, and may cost more or less. for many automotive components. Much like plastic, PMC • The processing (part fabrication) process will likely can be molded into complex shapes, thus integrating several run differently, and may operate much slower than steel or aluminum parts into a single PMC part that reduces that for the incumbent material (e.g., molding is much complexity and tooling costs. Conservative estimates are that slower than stamping, sometimes by a factor of 10). carbon fiber PMC can reduce the mass of a steel structure by 40 to 50 percent (Powers, 2000). Both its strength and its USCAR and the U.S. Department of Energy continue to stiffness can exceed that of steel, making it easy to substitute research reducing body mass by substituting new materials, for steel or aluminum while offering equal or better structural such as high-strength steel, advanced high-strength steel, performance. The greatest challenges with PMC are cost aluminum, magnesium, and composites for current materials. and carbon fiber availability. Also challenging is connect- The material industries also conduct significant research to ing composite parts with fasteners, which has delayed the advance new materials (for example, through the Auto-Steel introduction of the latest Boeing 787 Jet. Partnership, the American Iron and Steel Institute, the Alu- The price of carbon fiber is extremely volatile, with mate- minum Association, and the American Chemistry Council). rial cost typically in excess of $10/lb. Carbon fiber exceeds Increased costs for lighter and stronger parts result from the cost of steel and aluminum by approximately 20-fold and higher material costs and higher costs for component fabrica- 7-fold, respectively. Steel and aluminum can also be formed tion and joining. Estimates for the body-mass reduction that with high-speed stamping, which is much less costly than can be achieved in the near term vary from 10 percent (with forming PMC, which typically involves a fairly slow auto- mostly conventional and high-strength steels) to 50 percent clave process. Research at Oak Ridge National Laboratory (with a mostly aluminum/composite structure). Even greater (ORNL) is aimed at developing lignin-based carbon fiber to reductions are feasible, but these require very expensive and help reduce material cost and improve supply (Compere et aggressive use of aluminum, magnesium, and composite al., 2001). This research in conjunction with the FreedomCar structures involving materials such as carbon fiber. program at the United States Council for Automotive Re- search (USCAR) indicates that the price of carbon fiber has Non-Body Mass Reduction to fall to $5 to $7 per pound (about 50 percent) before it can be cost competitive for high-volume automobiles (Carpenter, Vehicle interiors also offer opportunities to reduce vehicle 2008). Lignin-based carbon fiber will also help ensure a mass. Some opportunities can be implemented for little

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103 NON-ENGINE TECHNOLOGIES cost, whereas others entail significant costs. For example, numbers,” and so original equipment tires tend to have lower composite-intensive instrument panels, recycled seating rolling resistance than consumer-replaced tires because materials, and lighter-weight trim panels can reduce mass typical values for the coefficient of rolling resistance (ro) by tens of pounds at virtually no cost. However, unlike the values differ between them (NRC, 2006). This represents an car body for which the consumer cannot easily detect what interesting value tradeoff. The OEMs are more interested in materials are used, the interior is aesthetically critical and getting low-rolling-resistance tires to show improved fuel closely scrutinized by the consumer. Costs may be incurred economy, and people buying replacement tires are more by covering over the appearance of some parts. There are interested in low cost and durability. Therefore the total op - quality concerns, such as fit-up of panels, part texture, and portunity for fuel consumption reduction is defined by the appearance issues that constrain interior cockpit design al - fraction of the tires on the road that falls into each category. ternatives. Some isolated components can have mass reduced Education of the public on the subject of low-rolling-resis- with material substitution such as headlamps (with new tance tires for replacement tires and the continued introduc - resins) and wheels (with new aluminum grades) that actu- tion of tire pressure monitoring systems, which is discussed ally enhance aesthetics but often increase cost. Non-visual below, may help improve in-use performance of tires for fuel parts, however, also present an opportunity, such as seat belt consumption reduction. reinforcements, seating frames/brackets, and fire wall panels. There are performance tradeoffs involving tires that tire Most non-structural applications that can be light-weighted manufacturers consider during design and manufacturing. with plastic already have been. Glass-reinforced sheet mold- These tradeoff variables include, for example, tread com- ing compound (SMC) is low cost and inexpensive to form but pound, tread and undertread design, bead/sidewall, belts, lacks sufficient strength to replace most structural applica - casing, and tire mass. Important tire performance criteria tions responsible for much of the weight. affected by design and manufacturing include rolling resis- Isolated components on the vehicles are also candidates tance, tire wear, stopping distance (stopping distance or grip for aluminum, magnesium, or advanced high-strength steel can be evaluated over different surfaces, such as wet or dry), substitution, such as wheels, engine cylinder heads, sus- and cornering grip. Wear and grip are closely correlated to pension arms, transmission cases, brake calipers, steering tread pattern, tread compound (e.g., softer compounds grip knuckles, and engine blocks, although many OEMs have better but wear faster), and footprint shape. already made these substitutions, especially in cylinder The impact of emphasizing one performance objective blocks and heads. Aluminum heads are more common than (such as low rolling resistance) over other performance aluminum blocks because of performance issues in the block, criteria is inconclusive. Some studies have shown that tires but other materials including hybrid materials (both alumi- with low rolling resistance do not appear to compromise num and cast iron) are being applied to the blocks. An even traction, but may wear faster than conventional tires. An- more aggressive approach to introducing aluminum into the other study in 2008 by Consumers Union and summarized structure itself will likely involve aluminum-intensive sub- by Automotive News (Automotive News, 2008) concluded structures (e.g., axle assemblies, engine compartment, etc.), that there may be a reduction in traction, because of low- and such components are also now starting to penetrate the rolling-resistance tires, that increases stopping distance. new-vehicle population. The study is not rigorously controlled, and other influ - Car glass (windshield, side windows, rear window, ences may confound the results. The response by one tire mirrors, and sun roofs) is also heavy, and there are oppor- manufacturer, Michelin (Barrand and Bokar, 2008), argues tunities to reduce mass by substituting polycarbonate. that low-rolling-resistance tires can be achieved without Polycarbonate can be coated to provide a durable finish, and sacrificing performance factors by balancing the design and this has been applied to non-windshield glass panels where manufacturing process variables. Tire makers are continuing scratching is less a concern. to research how to get optimal performance (including fuel economy) without sacrificing other criteria such as safety or wear. Goodyear points out that performance tradeoffs Rolling Resistance between rolling resistance, traction, and tread wear can be Tire rolling resistance is one of many forces that must be made based on materials and process adjustments, which overcome in order for a vehicle to move (see discussion in also affect cost (Goodyear Tire & Rubber Company, 2009). Chapter 2). When rolling, a tire is continuously deformed by The incremental cost for low-resistance tires may not be sig- the load exerted on it (from the vehicle mass). The repeated nificant, but the cost-benefit tradeoff with increased stopping deformation during rotation causes energy loss known as distance, wear, and possibly noise, vibration, and harshness rolling resistance. Rolling resistance is affected by tire issues are important for the consumer. design (for example, materials, shape, and tread design) and Rolling resistance can also be affected by brakes. Low- inflation. Underinflated tires increase rolling resistance. The drag brakes reduce the sliding friction of disc brake pads opportunity to improve fuel economy by reducing rolling on rotors when the brakes are not engaged because the resistance is already used by OEMs to obtain better “EPA brake pads are pulled away from the rotating rotor. Most

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104 ASSESSMENT OF FUEL ECONOMY TECHNOLOGIES FOR LIGHT-DUTY VEHICLES new vehicles have low-drag brakes. The impact over con- this may increase comfort, it is not clear whether this will ventional brakes may be about a 1 percent reduction of fuel significantly improve fuel economy (Rugh et al., 2007). consumption. • Exhaust heat recovery. Recent improvements in thermo- Rolling resistance is also affected by tire inflation, and electric materials for HVAC and exhaust energy recovery so any technology that affects inflation levels can also af- appear promising. Research is directed primarily at new ma- fect fuel economy. Reducing tire inflation levels increases terials with higher “thermoelectric figure of merit” (Heremans rolling resistance, which in turn increases fuel consump- et al., 2008; Hussain et al., 2009). This is accomplished by tion. A tire pressure monitoring system (TPMS) can be set increasing the thermoelectric effect (Seebeck coefficient) to different pressure thresholds, and the average deviation and reducing the thermal conductivity. Good results have from the recommended inflation level would be 1/2 the been obtained with nanomaterial processing, but at this time threshold level. For example, if the threshold is set at 10 psi, these are costly. Improvements in potentially low-cost bulk the average deviation from the recommended level would materials are needed for automotive applications. BMW has be 5 psi. Michelin believes that an accurate TPMS with an announced a planned introduction on production vehicles in the 2012/2013 model year.2 It presented a model of an ap- appropriately set threshold could reduce fuel consumption plication at the 2006 DEER Conference3 and in the press.4 by up to 0.7 percent (J. Barrand, personal communication, May 12, 2009). A DOE presentation gave more information on this vehicle and presented a rather optimistic view of energy recovery.5 In the view of the committee significant improvements need Vehicle Accessories to be made in the performance of bulk materials and in the Some automakers are beginning to introduce electric processing of nanomaterials before thermoelectric heat re- devices (such as motors and actuators) that can reduce the covery from the exhaust can be applied in mass production. mechanical load on the engine, reduce weight, and optimize The committee thinks that this will not happen in the 10-year performance, resulting in reduced fuel consumption. Of horizon considered here. course, the electrical power used by these devices must be furnished by the engine driving the alternator. Thus the most Transmission Technologies advantageous opportunities for converting mechanical de- vices to electrical are devices that operate only intermittently, Transmission technologies can reduce fuel consumption such as power steering and air-conditioning compressor. The in two ways, first by moving engine operation to more ef- benefits from electric and/or electro-hydraulic power steer- ficient regions of the engine map (cf. Figure 2.3 in Chap- ing and greater efficiency in air-conditioning (A/C) are not ter 2) and second by continued reduction of the mechanical credited by current EPA fuel economy tests (since neither losses within transmissions. Of these two, moving engine operates during the test), and so manufacturers are reluctant operation to more efficient regions of the engine map (e.g., to implement them because of added costs. With the new higher torque (or brake mean effective pressure; BMEP) and EPA test procedures, some of the benefits will be reflected in lower speeds) offers the largest potential gains. The major the “sticker,” and improvements in these areas are relatively approaches to achieving this movement are by increasing “low hanging fruit.” the number of speeds in the transmission (whether manual, automatic, or continuously variable) and lowering final drive • Heating, ventilating, and air-conditioning (HVAC). A ratio. more efficient system starts with (larger) heat exchangers Five-speed automatic transmissions are already a standard that transfer high heat more effectively and a thermal ex- for many vehicles; 6-, 7-, and 8-speed automatic transmis- pansion valve that controls the evaporator temperature. sions have been available on luxury cars and are penetrating The compressor uses the majority of the energy of the A/C into the non-luxury market. This new wave of automatic system, and variable displacement piston compressors are transmissions has been enabled by new power flow configu- available and in use that significantly reduce fuel use over rations and improved controls capability that are enabling fixed displacement compressors. There are many other tech- larger numbers of speeds to be achieved at a lower cost in- nologies, such as increased use of recirculated air, elevation crement over 4-speed automatics than would be the case for of evaporator temperature, use of pulse-width modulated adding speeds to previous automatic transmission designs. blower speed controllers, and internal heat exchangers, that can further reduce fuel usage. 2 S ee http://www.motorward.com/2009/02/new-details-on-next- Further reductions in fuel use can be achieved by decreas- generation-bmw-5-series/. ing A/C load through the use of low-transmissivity glazing 3 S ee http://www1.eere.energy.gov/vehiclesandfuels/pdfs/deer_2006/ (reducing both heat and ultraviolet penetration), reflective session6/2006_deer_lagrandeur.pdf. 4 See http://www.autobloggreen.com/2008/09/25/bmw-wins-koglobe- “cool” paint, and cabin ventilation while parked. Suppliers 2008-award-for-thermoelectric-generator/. are investigating the use of directly cooling the seat either 5 S ee http://www1.eere.energy.gov/vehiclesandfuels/pdfs/deer_2006/ through ducting or by thermoelectric materials. Although session6/2006_deer_fairbanks.pdf.

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105 NON-ENGINE TECHNOLOGIES This cost improvement resulted from transmission gear train market, but recent trends suggest that their usage may not synthesis optimization studies using computational tools grow further due to higher than expected costs and lower than that uncovered gear trains requiring fewer discrete elements expected internal efficiencies (EPA, 2008). because some of the elements (e.g., planetary gear trains) The issues discussed above generally apply to both SI and are utilized for multiple speeds. However, increasing the CI engines. However, the effects of moving engine operat- number of speeds always adds some components and their ing points to lower-speed and higher-torque regions of the associated cost. Along with higher numbers of transmission engine map are more beneficial for SI engines than for CI speeds, which allow operating engines in more efficient parts engines because intake throttling losses are reduced for SI of their fuel consumption map, transmission internal losses engines, whereas CI engines are not throttled. Nonetheless, are also being reduced, thus further improving power train for both CI and SI engines, fuel consumption is reduced efficiencies. by moving to higher-torque and lower-speed regions of the In addition to planetary-based automatic transmissions, engine maps because the relative effect of engine friction advanced versions of manual transmissions are also be- losses is reduced. ing introduced that can be more efficient than automatics Another important transmission issue difference between since torque converters are replaced by computer-controlled SI and CI engines is their peak torque. As noted in Chapter 5, clutches, which slip less than torque converters. These new CI engines produce higher maximum torques than do SI en- clutches not only are used to launch the vehicle from a stop gines. Maximum torque capacity is one of the most important but also enable rapid automated shifting of the manual gears criteria for durable transmission design, and so CI engines since one clutch can start engagement before the other clutch generally are mated with different, higher-torque-capacity has completely released. This class of manuals is called dual- transmissions than SI engines even in the same vehicle plat- clutch automated manual transmissions (DCTs).6 With this form. Sometimes, a given transmission used for SI engines concept, new-design manual transmissions are arranged with can be upgraded to higher torque capacity by more extensive two parallel gear trains, one for odd-numbered speeds and and more expensive heat treating of the gears and clutch the other for even-numbered speeds: for a 6-speed DCT, one upgrading, but frequently, different transmissions originally gear train would contain the first, third, and fifth speed gears designed for higher maximum torque capacity must be used while the other gear train would include the second, fourth, with CI engines, thus increasing cost, weight, and to some and sixth speed gears. DCTs are then coupled to the engine extent internal losses. through two clutches integrated into the transmission, one Another transmission-related technology that is appli- linking the odd-speed gear train to the engine and the other cable to both SI and CI engines is called idle-stop. This tech- clutch linking the even-speed gear train to the engine. Finally, nology is useful primarily for operation in cities and involves the clutches are actuated with electro-hydraulic systems cali- turning off the engine at idle. Benefits from idle-stop involve brated to provide smooth launch and rapid and smooth shift- eliminating most of the idle fuel consumption during the idle- ing, making them automatic in their interface to the driver. In stop period. Since idle fuel consumption is relatively large most of the current implementations of these clutches, they for SI engines due to throttling losses and the use of ignition are immersed in transmission oil, thus providing the cooling retard for smooth operation when accessories turn on and off, necessary for acceptable durability. Dry-clutch versions are FC reductions on the Federal Test Procedure (FTP) driving now also being developed for vehicles with lower torque cycle range from 3 to 5 percent. The real-world gain for requirements, making oil cooling unnecessary. Dry-clutch congested city driving (e.g., New York City) could be as high DCT designs are expected to be less costly to produce and as 10 percent since engines would be idled much more than lighter than their wet-clutch counterparts. In addition, dry- on the FTP test cycle. All idle fuel consumption losses are clutch DCTs will be more efficient through elimination of not eliminated since some accessories may need to operated the hydraulic pump work to cool the wet clutches. while the engine is stopped (e.g., A/C in hot climates), which Both automatic and DCT transmissions feature a discrete not only consumes some fuel but also increases component number of gear ratios that determines the ratio of engine cost by the necessity of replacing belt-driven accessories speed to vehicle speed. In contrast, a continuously variable with electrically driven ones. For the CI diesel vehicle, idle- transmission (CVT) offers a theoretically infinite choice of stop benefits are smaller than those attained with idle-stop for ratios between fixed limits, which allows engine operating SI gasoline vehicles because diesel engines have much lower conditions to be optimized for minimizing fuel consumption. idle FC than their gasoline counterparts. The estimated gain CVT technology has tended to be used in lower-horsepower on the U.S. cycle for CI vehicles is about 1 percent, although vehicles because of maximum-torque limitations with the the real-world gain for congested city driving (e.g., in New most common metal-belt design. A few OEMs offer CVTs York City) could be much higher. that utilize other drive schemes allowing usage with larger Other studies of vehicle fuel consumption (e.g., NRC, engines. CVTs have achieved some penetration into the 2002) have generally considered potential gains from trans- mission technologies in a separate category from engine efficiency technologies. In the present study, potential gains 6 See http://www.dctfacts.com/hmStory1b.asp.

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106 ASSESSMENT OF FUEL ECONOMY TECHNOLOGIES FOR LIGHT-DUTY VEHICLES from transmission technologies are considered together with directly proportional reduction of fuel consumption because those for engines. This choice was made for the following of (1) the accessory load and (2) the possibility that the reasons. For SI engines, the major opportunity for reducing power train may then operate at worse efficiency points. To fuel consumption (as is discussed extensively in Chapter 4) is take care of the power train efficiency it is necessary, at the reducing pumping losses. Many of the technology measures same time, to downsize the engine and/or change transmis- discussed in Chapter 4 reduce pumping losses in one way or sion shift points, because with a lighter load, the efficiency another. As noted above, the major impact of transmission of the power train is reduced, especially with SI engines that technologies toward reducing fuel consumption is to move will then operate with more throttling. Unfortunately, many the operation of the engine toward higher torque (or BMEP) studies on the impact of reducing Fm and Fa do not change and lower speeds at which pumping losses will be reduced. the engine operating points. For example, Barrand and Bokar As a result, there are significant interactions between engine (2008) do an excellent job of investigating the effect of roll- technologies that reduce pumping losses (e.g., valve event ing coefficient by changing tires without changing the power modulation) and transmission changes that also move engine train. Only an OEM designing a vehicle with low-rolling- operation to lower speeds and loads, such as increasing the resistance tires, for example, can fully take advantage of number of ratios and the associated ratio spread.7 A good rolling-resistance changes by reoptimizing the power train. example of these interactive effects is cylinder deactivation, Theoretically reducing any one of the three components as discussed in Chapter 4. When cylinder deactivation is by, say, 10 percent should reduce fuel consumption by used, the benefit of moving the engine operating point to roughly 3.3 percent since, as stated above, each component lower speeds and higher torques and higher BMEP is reduced accounts for roughly one-third of the total tractive energy. In compared to engines not using cylinder deactivation, because fact the size of the engine is determined by acceleration per- the working cylinders are already running at higher BMEP, formance requirements, as well as the tractive energy. There- thereby reducing pumping losses. Thus the fuel consumption fore all that can be said for certain is that reduction of all three reductions possible from increasing the number of transmis- components by an amount (say, X percent) would result in a sion ratios from 4 to 6, for example, would be lower for reduction in fuel consumption by roughly the same amount engines using cylinder deactivation than for those not using (X percent), assuming the power train were reoptimized. cylinder deactivation. This demonstrates how transmission- derived fuel reductions of fuel consumption cannot readily be Aerodynamics separated from engine-technology-derived fuel consumption reductions. This choice is reflected in the technology paths As discussed above, vehicles with higher Cd values discussed in Chapter 9. (over .30) may be able to have the Cd reduced by 5 percent or so (up to 10 percent) at low cost. The associated impact on fuel consumption and fuel economy could be 1 to 2 FUEL CONSUMPTION BENEFITS OF NON-ENGINE percent, and this assumes that the engine operating regime TECHNOLOGIES is not modified. If lower acceleration can be tolerated and The tractive force that is needed to propel a vehi - the engine operates at the same efficiency, the improvement cle can be written simply as the sum of three forces: with a 10 percent reduction of aerodynamic drag could be as high as 3 percent (10 percent × 0.3). Argonne calculations FTR = Fm + Fr + Fa for the improvement in fuel consumption show that without engine modifications a 10 percent reduction in aerodynamic where Fm accelerates the mass, Fr overcomes rolling resis- drag would result in about a 0.25 percent reduction in fuel tance, and Fa overcomes aerodynamic drag. The integral consumption for the urban cycle and a 2.15 percent change of this force over a given driving cycle gives the amount of for the highway cycle. energy required at the wheels. Using typical values in Equa- tion 2.1 one can calculate that for the EPA combined cycle Car Body Design and Interiors about one-third of the tractive energy goes into each of these three components (see Table 2.7). However, as Table 2.7 It is well established that a reduction in vehicle mass re- shows for the urban cycle, Fm is around 60 percent of the duces fuel consumption. The specific relationship between total and for the highway cycle, Fa is about half. Before giv- mass reduction and fuel consumption, however, is complex ing estimates of the benefits of fuel-saving technologies, it and depends on many factors: is necessary to make two important points. Merely reducing tractive energy does not translate into a • Amount of mass reduction, • Driving cycle, 7 Ratio • Type of engine, and spread is defined as the ratio of first gear divided by the ratio of the top gear. As an example, for a typical 6-speed automatic transmis - • Secondary benefits, such as whether or not other ve- sion, the low-gear ratio would be 4.58:1 while that of the sixth gear would hicle systems are redesigned to match the new vehicle be 0.75:1. The ratio spread would then be 4.58/0.75, which equals 6.1.

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107 NON-ENGINE TECHNOLOGIES mass, as with, for example, engine downsizing, retuned fuel economy impact; Table 7.3 shows the range of impact transmission, and reduced components for crash man- on fuel economy for all types. agement, braking, fuel storage, and so on. Table 7.3 shows the results of the Ricardo, Inc., simulation calculating the potential impact on fuel consumption from A midsize car body structure with closure panels (no reduction of mass. The range shown in the results is due to trim or glass) can weigh approximately 800 pounds (about summarizing a composite of simulation runs for different 25 percent of the vehicle’s total curb weight). Should the vehicle models and power trains. This discrepancy (range mass reduction be significant, a secondary benefit can of fuel economy impact) in fuel economy improvement in- accrue from reducing the size of the needed power train, creases for different vehicle types as the reduction in mass braking systems, and crash management structures. These increases from 5 to 20 percent. However, if the engine is secondary benefits are difficult to estimate but can poten - resized to match each level of mass reduction (to maintain tially approach an additional 30 percent reduction in mass, original vehicle performance), the range of fuel economy and these secondary benefits can help offset the cost of the improvement across the vehicle classes is fairly small. This initial effort (IBIS Associates, 2008). observation points to the importance of matching engine A basic estimate of the relationship between fuel econ- performance to vehicle mass. For small (under 5 percent) omy and mass is provided by the Department of Energy changes in mass, resizing the engine may not be justified, but (Carpenter, 2008) and also by the Laboratory for Energy and as the reduction in mass increases (greater than 10 percent), Environment at the Massachusetts Institute of Technology it becomes more important for certain vehicles to resize the (Cheah et al., 2007). A rule of thumb is a 6 to 8 percent im- engine and seek secondary mass reduction opportunities. provement in fuel economy (or, equivalently, a reduction of Physical vehicle testing has confirmed the reductions 5.7 to 7.4 percent in fuel consumption) for every 10 percent in fuel consumption associated with reductions in vehicle drop in weight when secondary benefits are included that mass. For an internal combustion engine, the effect of mass indirectly accrued from having lower mass. reduction is greater with a city driving cycle versus a high- In a study conducted by Ricardo, Inc. (2007), and spon- way cycle because of the frequent acceleration/deceleration sored by the Aluminum Association, this relationship was of mass. For example, vehicles (combination of compact, simulated for several vehicles loaded with from 2 to 5 pas- midsize, and SUV classes) powered by internal combustion sengers. The gasoline-powered vehicles simulated are listed engines can reduce fuel consumption approximately as fol- in Table 7.2. lows (Pagerit et al., 2006): 0.1 gallon per 100 miles driven Two scenarios for these vehicles were simulated. The can be saved with, approximately, first scenario evaluated the impact on fuel economy when everything about the vehicle remained unchanged except • 190 pounds mass reduction—city cycle, and for a reduction in vehicle mass. The second scenario re - • 285 pounds mass reduction—highway cycle. sized the engine to reflect comparable vehicle performance (the benefits of other reductions in mass such as a smaller As discussed in Pagerit et al. (2006) and further supported by gas tank, smaller brakes, etc. were not included). In this the Ricardo, Inc., study, the improvement gained from reduc- scenario, the engine required less power because of the tion of mass (expressed as fuel consumption and not miles reduction in mass, and therefore, fuel economy was further per gallon) is the same regardless of the weight of the vehicle. improved. The vehicle type was not a major differentiator of Unlike changes in rolling resistance and aerodynamics, re- TABLE 7.2 Vehicle Mass Assumptions for Ricardo, Inc. (2007) Study to Assess Effects of Mass Reduction on Fuel Economy Type of Vehicle Initial Weight (lb) Load Weight (lb) 5% Reduction (lb) 10% Reduction (lb) 20% Reduction (lb) Small car 2,875 300 3,031 2,888 2,600 Midsize car 3,625 450 3,894 3,713 3,350 Small SUV 4,250 550 4,588 4,735 3,950 Large SUV 5,250 750 5,738 5,475 4,950 NOTE: The 5 percent, 10 percent, and 20 percent mass reduction applies to the initial vehicle weight and not the load. TABLE 7.3 Impact on Fuel Consumption Due to Reduction of Mass in Study by Ricardo, Inc. (2007) Vehicle Mass Reduction from Baseline Vehicle 5% Mass Reduction 10% Mass Reduction 20% Mass Reduction Mass reduction only 1-2% 3-4% 6-8% Mass reduction and resized engine 3-3.5% 6-7% 11-13%

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108 ASSESSMENT OF FUEL ECONOMY TECHNOLOGIES FOR LIGHT-DUTY VEHICLES Vehicle Accessories ducing mass not only reduces the amount of tractive energy needed but also permits a reduction in power train (engine The opportunity may exist to decrease fuel consumption downsized or transmission shift changes) without adversely (in gallons per 100 miles driven) by about 3 to 4 percent with affecting performance (acceleration). A 10 percent reduction a variable-stroke HVAC compressor and better control of in mass and power for the reference vehicle should reduce the amount of cooling and heating used to reduce humidity fuel consumption by about 5.7 to 7.4 percent (or 6 to 7 (Table 7.4). Estimates for further reductions that can be percent). In a conventional vehicle, the energy used to ac- achieved by decreasing air conditioner load through the use celerate the mass is mostly dissipated in the brakes, whereas of low-transmissivity glazing, reflective “cool” paint, and in a hybrid, a significant fraction of this braking energy is cabin ventilation while parked have not been determined. recovered, sent back to the battery, and reused. Thus, mass According to a Deutsche Bank report, electro-hydraulic reduction in hybrid vehicles is less important than in conven- power steering (EHPS) would reduce fuel consumption by 4 tional vehicles. The complexity of mass reduction increases percent with an incremental cost of $70, while electric power when a conventional vehicle is compared with either a hy- steering could improve 5 percent with an incremental cost brid (which incurs additional battery mass) or a CI engine of $120, but there is little information on how this estimate (which has greater power train mass). While reducing mass was obtained (Deutsche Bank, 2008). A TRW study (Gessat, will always provide a fuel economy benefit, changing tech- 2007) showed that while a conventional hydraulic power nology pathways (between SI, CI, or hybrid designs) has to steering system consumed 0.35 L/100 km, the best TRW recognize the impact that the new technology has on mass. electro-hydraulic steering system consumed 0.07 and an electric power steering system 0.02. These figures are relative Rolling Resistance to a small vehicle with a 1.6-L engine. In its study of CO2- reducing technologies for the EPA (EPA, 2008), Ricardo, A report on tires and fuel economy (NRC, 2006) estimates Inc., found that electric power steering (EPS) reduced com- that a 10 percent reduction in rolling resistance will reduce bined fuel consumption by about 3 percent based on FSS fuel consumption by 1 to 2 percent. This reduction, however, calculations. From this and the estimates provided in recent is without changes in the power train. If the power train could regulatory activities by NHTSA and EPA, the committee be adjusted to give the same performance, then the benefit estimated that EPS reduces combines fuel consumption by of a 10 percent reduction would be on the order of as much about 1 to 3 percent on the EPA 55/45 combined cycle, which as 3 percent. Underinflated tires that are 20 percent below is the basis for the CAFE standard. However, the committee recommended inflation pressure (say, 35 psi) increase rolling recognizes that the reduction of fuel consumption could be resistance by 10 percent, and thus increase fuel consumption as high as 5 percent under in-use driving conditions. by 1 to 2 percent (Goodyear Tire & Rubber Company, 2009). Again as discussed above under “Aerodynamics,” if a re- Transmission Technologies duction in rolling resistance is combined with a reduction in aerodynamics and mass, the power train can be significantly Fuel consumption reductions generally increase with modified to improve efficiency. As indicated in Chapter 2, additional transmission speed ratios, although interaction rolling resistance accounts for about a third of the energy effects between engine technologies that reduce pumping going to the wheels for the city as well as the highway cycles. losses and increase the number of transmission speeds are Reducing mass, aerodynamics, and rolling resistance by 10 important, as noted earlier. However, since the costs also percent reduces fuel consumption by about 10 percent with increase and the marginal gain for each additional speed power train resizing and other drive train adjustments (e.g., gets smaller, there are diminishing returns. Table 7.5 lists changes in transmission shift points, axle ratios). As noted the transmission technologies and estimated reductions in earlier, vehicle mass reduction for a hybrid is not as effective fuel consumption. The basis of this table is baseline engines since some of the energy going to the brakes is recovered. TABLE 7.4 Potential Reduction of Fuel Consumption with the Use of Vehicle Accessories Reduction in Fuel Vehicle Accessory Consumption (%) Comments Variable-stroke HVAC compressor 3-4 Improved cooling, heating, and humidity control Low-transmissivity glazing, cool paint, ~1 Lower heat buildup in vehicle decreases air-conditioning load parked-vehicle ventilation Electrohydraulic power steering 4 Combined electric and hydraulic power for midsize to larger vehicles reduces continuous load on engine Electric power steering 1-5 Electric power steering for smaller vehicles reduces continuous load on engine— smaller benefits (1-3%) estimated for the FTP

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109 NON-ENGINE TECHNOLOGIES without significant valve event modulation technologies or Automobile manufacturers differ significantly in their ap- cylinder deactivation. proach to introducing new products. Manufacturers based in Asia, for example, are known for having shorter product life cycles but often implementing lower levels of engineering TIMING CONSIDERATIONS FOR INTRODUCING NEW redesign at changeover. Manufacturers based in Europe and TECHNOLOGIES North American have traditionally had longer product cycles The timing for introducing new fuel consumption technol- with a greater amount of engineering applied at changeover. ogies can significantly influence cost and risk. The maturity There are always exceptions to these generalities even within of a technology affects its cost and reliability. Automobile a manufacturer, depending on the vehicle model. The strat- companies have sophisticated product and process validation egy to implement engineering changes on a regional vehicle procedures that must be adhered to before products can be (e.g., North America only) versus a global platform can scaled up for mass production, or they expose themselves to greatly impact timing and cost. Entire textbooks have been large warranty or product liability concerns. Many vehicle written around product timing for manufacturers, and so a changes are timed for implementation around the product discussion here can at best only introduce the inherent issues development process to minimize cost and quality concerns. that affect cost and timing for any manufacturer. Lower-volume and higher-end vehicles often have new tech- Generally, 2 to 3 years is considered the quickest time nologies applied first for several reasons. The lower volumes frame for bringing a new vehicle to market. A significant mitigate the exposure to risk, and the higher-end vehicles amount of carryover technology and engineering from other can bear the higher initial early cost of a new technology. models (or previous vehicle models) is usually required to During this period, competition brings the technology cost launch a new vehicle this quickly. In some cases, so much down while the supply chain develops for higher volumes of the vehicle is replicated that the new vehicle is consid- in the future. ered a “freshened” or “re-skinned” model. The ability to An important consideration for introducing new technolo- significantly influence vehicle performance (e.g., through gies that have broad impact concerns the product develop- light-weighting, changing power trains, etc.) is minimal be- ment process of new vehicles. Aggressive use of lightweight cause so much of the vehicle is unchanged. More substantial materials to obtain secondary benefits; power train modi- changes to the vehicle occur over longer periods of time. fications; and body shape modifications (to improve aero- Newly styled, engineered, and redesigned vehicles can take dynamics), for example, may have to be timed with future from 4 to 8 years, each with an increasing amount of new product development phases. Although material substitution content. for components can occur throughout the life cycle of a car Automobile producers generally have product develop- in many cases, the mass saved in this way is relatively minor. ment programs (PDPs) spanning at least 15 years. PDPs Considering how to reduce mass to achieve greater energy are extremely firm for 3 to 5 years due to the need for long- savings requires a broad systems evaluation and reengineer- lead-time items such as tooling or supplier development ing of the vehicle. Once a vehicle has been validated and requirements, and the need for extensive testing of major tooled for a specific design and production has begun, new items such as those required for fuel economy, emissions, development costs are planned for future model changes. and safety regulations, and confirmation of reliability and Most significant modifications have to occur around various durability. In general, model changeovers can be catego- phases of the vehicle’s production life. rized into five areas (freshen, re-skin, restyle, reengineer, TABLE 7.5 Transmission Technologies and Estimated Reductions in Fuel Consumption Fuel Consumption Reductiona (%) Technology Comments Five-speed automatic transmissions 2-3 Technology can also improve vehicle performance Six-speed automatic transmissions 3-5 Seven-speed automatic transmissions 5-7 Eight-speed automatic transmissions 6-8 Dual-clutch automated manual 6-9 Original automatic transmissions with conventional manual transmissions transmissions (6-speed) (DCT) supplemented with electro-hydraulic clutch and shift actuators have been replaced with DCTs Continuously variable transmissions 1-7 Some issues related to differences in feel and engine noise; improvements depend on engine size NOTE: Values based on EEA (2007) with adjustments to reflect range of values likely to occur. aImprovements are over a 2007 naturally aspirated SI-engine vehicle with 4-speed automatic transmission of similar performance characteristics.

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110 ASSESSMENT OF FUEL ECONOMY TECHNOLOGIES FOR LIGHT-DUTY VEHICLES nologies over a 15-year life cycle can be substantial, and and redesign; see Automotive News, July 14, 2008, p. 28). the performance improvement for fuel consumption can be These five categories and their potential for effecting fuel substantial with a new power train. consumption improvements are described in Table 7.6. It The estimates in Table 7.6 are based on business as usual. is not accurate to say that every vehicle progresses through The “frequency” is the time from concept through proto- every one of these phases. It is possible to skip a re-skin and typing, production vehicle design, tooling release, verifica- jump to a restyle, for example. Also, not every vehicle will tion testing on preproduction vehicles, and start of full-scale be redesigned in 6 to 8 years because many factors affect production. Shorter time frames are possible, especially if this timing (market demand, finances, etc.). The potential more vehicle content is carried over between PDPs to reduce for impacting fuel consumption is only a rough approxima- engineering, testing, etc., but this limits the degree of model tion, and none of these estimates consider the inclusion of changeover. Urgency to introduce new vehicles (e.g., smaller hybrid or alternative power trains. The estimates for reducing and more fuel efficient vehicles) can accelerate the nominal fuel consumption shown in Table 7.6 are not additive (from duration of each PDP phase, but the investment cost will grow. previous changeover phases). Fuel consumption estimates Modest improvements in fuel consumption can be achieved also assume comparable vehicles of the same size and per- early in the PDP cycle (e.g., freshen and re-skin stages) by formance (including crash worthiness, electronic content, introducing more aerodynamic designs and low-rolling- and other factors that are often adjusted with new vehicles). resistance tires. A greater impact on reducing fuel consump- The engine development process often follows a path tion can come from changes in engine, transmission, and mass separate from those of other parts of the vehicle. Engines reduction later in the PDP when the vehicle is redesigned or have longer product lives, require greater capital investment, reengineered. Restyled vehicles allow for material substitu- and are not as critical to the consumer in differentiating one tion on a part-by-part basis, but without changing entire vehicle from another as are other aspects of the car. Also, subassembly structures. Often, the substitution might be for a consumer-driven changes for styling change faster than the higher-strength metal with a thinner gage in place of the cur- need to introduce new power train technologies. The power rent material. Tooling and assembly processes may be altered train development process evolves over closer to a 15-year somewhat to accommodate the new material. A reengineered cycle, although refinements and new technologies will be vehicle allows for changing the design of major subassemblies implemented throughout this period. Also, because of the (engine compartment, closure panels, body sides, etc.), thus complexity, costs, and resources required to launch a new allowing for entirely new approaches to reducing mass. Re- power train, it is unusual to launch a new engine-related engineered vehicles normally require crashworthiness testing transmission simultaneously. The development of new tech- TABLE 7.6 Vehicle Product Development Process (non-power train) and Timing Implications to Effect Fuel Economy Changes Type of Model Frequency Fuel Consumption Opportunities to Impact Fuel Investment Change (Years) Description Reduction Consumption Cost Freshen 2-3 Sheet metal untouched, may include new Little to none Minor impact on mass; possible Low (≤3%) grille, fascia, headlights, taillights, etc. impact with aerodynamics and tires Re-skin 3-5 Minor changes to sheet metal Little to none Same as above and vehicle Modest (≤5%) accessories Re-style 4-8 Extensive changes to exterior and interior Minimal Some impact on mass (mostly High (5-8%) interior components); possible impact with aerodynamics, tires, and vehicle accessories Re-engineer 4-8 Extensive makeover of vehicle’s platform, Moderate Mass reduction opportunity with Very high chassis, and components to reduce noise, (7-14%) part-by-part material substitution vibration, and harshness and improve (e.g., aluminum or high-strength qualities such as ride, handling, braking, steel); possible impact with and steering (this degree of change or the aerodynamics, tires, and vehicle next may require recertification and crash accessories testing), body restyling often concurrent with this phase Redesign A 6-8 New platform, new interior and exterior Significant Entire vehicle structure—opportunity Very high styling; engine and transmission carried (13-18%) to introduce lightweight materials over; some structural subsystems possibly throughout entire vehicle; impact reengineered from aerodynamics, tires, and vehicle accessories

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111 NON-ENGINE TECHNOLOGIES and incur significant additional costs because of the reengi- as carbon fiber will need significant cost reduction and neered designs. The redesigned vehicles start with a “clean supply chain development over the next 15 years. The com- sheet” affording the benefits of a reengineered vehicle, along mittee does not expect to see significant inroads in this time with more optimal matching of the power train to the lighter- frame by this technology except in low-volume (specialized weight structure. In general, a redesign results in a new vehicle applications), high-performance vehicles. Other polymer/ platform that in many cases replaces existing vehicles. reinforced composites, etc. will continue to make inroads in the vehicle interior where steel or aluminum is used currently for strength. For example, all-polymer/reinforced composite Aerodynamics instrument panels (without rear steel reinforcements) are Reductions of drag coefficient Cd by 5 percent or so (up likely to make it to production soon. to 10 percent) have been taking place and will continue. A As production processes continue to be developed, 5 percent reduction in aerodynamics can be achieved with broader application of both magnesium and titanium can minimal cost through vehicle design, and larger reductions be expected, such as for magnesium engine blocks that can be achieved by sealing the undercarriage and installing weigh approximately 30 pounds less than aluminum ones covers/shields (e.g., in the wheel well areas and underbody). (see Table 7.7). Magnesium will likely make inroads for Elimination of outside rear view mirrors will require changes component parts such as suspension arms and interior dash in safety regulations and improvement in vision systems. panels and seating brackets. Titanium will continue to find Since these changes can be costly, they are unlikely to be application in suspension springs, valve springs, valves, implemented soon except on high-end vehicles. In the longer connecting rods, and exhaust systems, resulting in 35 to 40 term (about 10 years), 5 to 10 percent reductions in aero- percent savings in mass over steel components. dynamic drag are plausible, but this may come with some compromise in vehicle functionality. Rolling Resistance Low-rolling-resistance tires are already used by OEMs. Car Body Design and Interiors The committee does not expect significant additional im- Reductions in weight have been taking place and will provements without sacrificing performance. Since replace- continue in the near term with reductions from 10 percent ment tires are on most vehicles on the road today, a campaign (with mostly conventional and high-strength steels) to 25 to educate purchasers of replacement tires of the possibility percent (with high-strength steel structures, aluminum clo- of fuel savings is a good way to reduce fuel consumption. sure panels, and body/interior components made from vari- More vehicles today are being offered with low-tire-pressure ous lightweight materials). Table 7.7 provides an overview of monitors to warn the driver of underinflated tires for safety the timelines for the introduction of new materials for vari- and fuel economy. ous vehicle components. Today’s new vehicles already are composed of upward of 40 to 50 percent high-strength steel Vehicle Accessories (over 480 MPa yield strength), but higher-strength steels (ad- vanced high-strength steels) are being developed (up to 1,000 Variable stroke compressors and reduction of subcooling MPa) that could replace even the current high-strength steel. are being developed and should appear in vehicles in the next Various vehicle components for which isolated material sub- 3 to 5 years. Because the current duty cycle measuring fuel stitution can take place will also be the norm. For example, consumption does not recognize HVAC systems, there is no Ford recently indicated that aluminum calipers replaced steel motivation to introduce these systems because they incur ones, thus saving 7.5 pounds per vehicle. Also, aluminum additional costs. However, the proposed new EPA test proce- wheels replaced steel wheels, resulting in 22 pounds saved dure may cause new interest in introducing this technology. per vehicle. More aggressive application of aluminum to car doors can also save another 20 pounds per door, but at a COSTS OF NON-ENGINE TECHNOLOGIES higher cost. Substitution of material in other components can also be expected, including the wiring harness. Substituting Aerodynamics copper-clad aluminum wiring for all copper wiring can save 10 or more pounds per vehicle, but usually at a higher cost. A 5 percent reduction in aerodynamics can be achieved More aggressive reduction of mass is feasible at higher with minimal cost through vehicle design. Slightly more cost if aggressive targets of greater than 25 percent are set. aggressive reductions can be achieved by sealing the under- Reduction of mass at the 50 percent level can be attained in carriage and installing covers/shields (e.g., in the wheel well the body with a mostly aluminum structure (probably using areas and underbody) costing in the tens of dollars. A 10 a space frame design), but this approach will be cost prohibi- percent reduction in aerodynamics may be aggressive, call- tive under most conditions for high-volume vehicles. ing for wind deflectors (spoilers) and possibly elimination of The use of composite structures involving materials such rear view mirrors, which would cost a few hundred dollars.

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112 ASSESSMENT OF FUEL ECONOMY TECHNOLOGIES FOR LIGHT-DUTY VEHICLES TABLE 7.7 Estimated Timeline for Introduction of New Materials by Type of Component Timing High-Strength Steel Aluminum Magnesium Plastics and Polymer—Composites Current or near Body rails, door sills, B-pillar, Hood, deck lid, engine block Instrument panel, Truck box term (3-5 side roof rails, underbody, and cylinder lining, front seat components Outer skin panels (doors, fenders, etc.) years) front suspension subframe, suspension subframe, bumper Brackets Instrument panel bumper beams, cross- beams, rear suspension Crash structures Bumpers members, brackets and knuckles, steering hanger Intake manifold Trim reinforcements, exterior beam, power train components Engine parts (intake manifold, cover, body panels, body side ring, (castings), condenser/radiator etc.) longitudinal rails, wheels wiring harness Future Same as above, only with Doors, exterior body panels Door, inner Body side ring (5-10 years) higher-strength steels (fender, roof) Engine block Roof Side pillar (B or C) Underbody Seat components Sound dampening Glass (polycarbonate) Long term New steels with greater Increased applications Limited increase New materials will be developed with (>10 years) formability allowing (depending on material in applications; higher strength, allowing them to application to more cost); subassemblies such as possibly be applied to more structural parts. complex part shapes and engine compartment, chassis, transmission Mixed-material bonding will be exterior panels; less steel instrument panels; overall, more parts developed. Overall, more plastics/ overall in the vehicle aluminum in the vehicle polymers will be in the vehicle. Car Body Design and Interiors many incumbent steel parts or assemblies, and the structural components that are among the heaviest parts offering the The term “material substitution” often misrepresents greatest opportunity will be targeted. Plastics, composites, the complexity and cost comparison when one material is and other metals (magnesium and titanium) will be used on substituted for another one. The cost to change materials in a somewhat limited basis because of cost. the vehicle, from an incumbent material to a lighter-weight In recent years, reductions in mass have been realized material, is a function of capital and variable costs: in the body, interior, and power train by introducing new materials such as high-strength (and advanced high-strength) Fixed Costs (up-front investment costs) steels, plastics (not including carbon fiber), and aluminum. • Design and engineering Magnesium has also been used to reduce mass, but to a much • Prototype development and testing lesser extent. In the near future (5 years), the committee ex- • Tooling: fabrication, dimensional measurement, pects continued mass reduction following the same pattern; and assembly through continued introduction of more and higher-strength steels, aluminum, plastics/polymers, and to a lesser extent Variable Costs (a function of the volume of production) other materials such as magnesium. • Production and assembly labor cost Although there are research and development costs to • Production equipment develop new high-strength steels and new manufacturing • Material processes for them, once developed they have minimal net • Joining (welding, adhesive, sealing, riveting, etc.) long-term incremental cost over mild steel. Tooling, fabrica- tion, and joining costs tend to be higher for these materials be- An added complexity results with material substitution cause of the material strength, which has to be added to the net because part design is material dependent, and the redesigned cost difference. Although the cost per pound of high-strength part may provide (and often does) different functionality steel is higher than mild steel, less of it is needed. Hence, a than the original part. For example, a molded plastic part 10 or 20 percent material cost premium will be offset by us- can take on more complexity than a formed steel part, and ing 10 to 20 percent thinner steel. As high-strength steels are so the direct comparison should also take the difference in introduced, their net incremental cost approaches zero after a functionality into account. Also, two or more parts may get period of maturity. The DOE estimates that, on average, sub- integrated into a single part with one material versus that of stituting high-strength steel for mild steel results in about a net another, and so the subsystem of parts has to be evaluated increase in material cost of 10 percent (see Carpenter, 2008). for a cost and performance comparison. The cost to reduce mass (cost per pound of mass reduced) Most cost-effective materials today for reducing mass are increases as the amount of reduced mass increases. The “low high-strength steel and aluminum. Both materials can replace

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113 NON-ENGINE TECHNOLOGIES hanging fruit” of mass reduction using high-strength steel in these components have been light-weighted already with basic applications can result in less than a 10 percent cost high-strength steel and aluminum where practical. One next premium. However, increasingly aggressive reduction of step would be to transition to more magnesium, which comes mass requires more difficult parts and materials whose cost with a cost premium of perhaps 50 percent or more over that exceeds the 10 percent premium. For example, a 1 percent for aluminum. reduction in mass can generally be achieved at a multiplier of 1.0 to 1.1. More aggressive applications likely require more Secondary Savings Benefits expensive materials or more expensive fabrication and join- ing methods, or affect the costs of other parts in the vehicle. An important consideration with mass reduction is that its As the aggressiveness increases (to 5 percent, 10 percent, or effects on fuel consumption can cascade. As the mass of a ve- even 20 percent), more materials and processing options need hicle is reduced in, say, the body or interior, other components to be considered that further increase cost. The committee of the vehicle can be reduced in size as a consequence. For believes that a 10 percent reduction in mass is achievable example, brakes, fuel system, power train, and even crash- with a mix of materials (high-strength steels, aluminum, management structures can all be downsized for a lighter composites, and other metals) for approximately $2.00 per vehicle. In the study conducted by Ricardo, Inc., (2007) for pound of mass eliminated (see Table 7.8). More aggressive the Aluminum Association, the rule of thumb generated was reductions will cost more than $2.00 per pound. that for every pound eliminated in the vehicle structure, an ad- Aluminum costs more than steel and has some forming ditional 0.30 lb (30 percent) of mass could be reduced in other and joining limitations that prevent its use in some applica- areas of the vehicle. If this rule of thumb is applied and mass tions. An incremental cost of aluminum over steel body reduction comes at a cost of $1.65/lb, then at an additional parts in the range of 30 to 100 percent has been estimated 30 percent of secondary mass savings (0.3 lb) the net cost per (Carpenter, 2008; Bull, 2008). The Aluminum Association pound becomes $1.65/1.3 lb, which becomes $1.27/lb. It is estimates that the average increment is 30 percent at the low important to note that achieving secondary savings typically end (premium cost per pound of mass eliminated). At the requires reengineering one or more systems on the vehicle, mid-point of this range, the incremental cost is $1.65/pound and this would likely be performed according to the product of mass eliminated. Higher costs will be incurred (approach - development timing plan (see above the section “Timing ing $2.00/lb cost premium) as more aggressive reduction of Considerations for Introducing New Technologies”). So the mass reduction is attempted. 30 percent secondary benefit is achieved in the long term and The body of a baseline vehicle (mostly steel) weighs ap- not necessarily when the initial reduction in mass is achieved. proximately 800 pounds. An aluminum-intensive body weighs approximately 45 percent less, or 440 pounds. The estimated Rolling Resistance cost for this savings in weight is in the range of $468 ($1.30/lb) to $594 ($1.65/lb). Mass reduction in other vehicle systems The incremental cost for low-rolling-resistance tires is es- such as power train, wheels, chassis, and interior would typi- timated to be $2 to $5 per tire, but there is some evidence that cally come at similar or slightly higher incremental cost per suggests that these tires may slightly compromise stopping pound saved. Vehicle interiors (including seats, door trim, distance. One tire manufacturer suggested that tires that do headliners, instrument panel components, etc.) constitute ap- not compromise stopping distance or tread wear could cost proximately one-third of the vehicle mass (1,000 pounds in a 10 to 20 percent more than conventional tires. (Note: The 3,000-pound vehicle). By using lightweight materials, Byron uncertainty about low-rolling-resistance tires with respect to Foster at Johnson Controls plans to eliminate 30 percent of the increased tread wear and stopping distance is the reason for interior mass (Forbes, 2008). If the same incremental cost used increasing the estimated cost beyond the $1.00 per tire cost for the body is assumed, approximately 300 pounds eliminated cited in NRC (2006). The NRC (2006) study recognized that would cost $390 ($1.30/lb) to $495 ($1.65/lb). an acceptable increase in tread wear and stopping distance Other opportunistic components in the vehicle include might occur. However, to eliminate this increase, additional the power train, chassis, and wheel components. Many of costs can be expected over the $1.00 estimate.) TABLE 7.8 Committee’s Estimate of Cost to Reduce Vehicle Mass (based on 3,600-lb vehicle) Mass Reduction Low Cost/lb High Cost/lb Average Cost/lb Mass Saved Low Total Cost High Total Cost (%) ($) ($) ($) (lb) ($) ($) 1 1.28 1.54 1.41 36 46.08 55.30 2 1.33 1.60 1.46 72 95.76 114.91 5 1.50 1.80 1.65 180 270.00 324.00 10 1.80 2.16 1.98 360 648.00 777.60

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114 ASSESSMENT OF FUEL ECONOMY TECHNOLOGIES FOR LIGHT-DUTY VEHICLES Vehicle Accessories a transmission. As a result, the number of cost estimates available to the committee was limited. When additional in- Table 7.9 shows the committee’s estimates of the costs for formation was sought by the committee, the results reflected vehicle accessories that could improve the fuel consumption the still-emerging knowledge base about this transmission of light-duty vehicles. type. One estimate, based on a detailed teardown study conducted by FEV, Inc., for the EPA, estimated the cost Transmission Technologies of 6-speed DCTs with 350 N-m torque capacity and wet clutches at over $147 less than that for a 6-speed automatic The estimated retail price equivalent for each transmis- (Kolwich, 2010). However, OEMs considering tooling up sion technology is provided in Table 7.10. As was the case their own equivalent units had also made careful estimates of for the engine technology chapters (e.g., Chapters 4 and 5), the high-volume piece cost increase of DCT6s. These OEM the baseline for transmission costs is the 4-speed automatic estimates were that high-volume DCT6s would cost nearly typical of 2007 model-year vehicles. Cost estimates are from $200 more than 6-speed automatics. Thus, the range between the two sources considered (EEA, 2007; Martec Group, Inc., estimates was approximately $350. At the present time, in- 2008). As can be seen from Table 7.10, the cost estimates for sufficient information is available to narrow this wide range. the 5-, 6-, 7-, and 8-speed automatic transmission replace- ments for the baseline 4-speed automatic have a considerable SUMMARY numerical range. In addition to the cost estimates, Table 7.10 also includes cost estimates converted to RPE using the RPE There is a range of non-engine technologies with varying multiplier of 1.5. Besides the estimates for 5-, 6-, 7-, and costs and impacts to consider. Many of these technologies 8-speed automatic transmission replacements, estimates are are continually being introduced to new vehicle models also included for DCTs and CVTs. The DCT estimates reflect based on the timing of the product development process. an even wider numerical range than those for the automatics. Coordinating the introduction of many technologies with For example, the 6-speed automatic cost estimates range the product development process is critical to maximizing from $133 to $215, whereas the estimates for the wet-clutch, their impact and minimizing their cost. Relatively minor 350 N-m torque capacity range from $140 to $400. changes that do not involve reengineering the vehicle can Although DCT units have been in high-volume produc- be implemented within a 2- to 4-year time frame. This tion for a number of years, until recently only the VW-Audi could include efforts such as aiming for minor reductions group, working closely with one supplier, has produced such TABLE 7.9 Estimated Incremental Costs for Vehicle Accessories That Improve Fuel Consumption Description Source of Cost Estimate Estimate HVAC—variable stroke, increased efficiency (humidity control, paint, glass, etc.) $70-$90 U.S. Environmental Protection Agencya Electric and electric-hydraulic power steering Deutsche Bank $70-$120 Thermoelectric energy recovery Several hundred dollars aThe U.S. EPA has estimated the cost associated with improving the energy efficiency of the A/C system and reducing refrigerant leakage from the system at less than $110 to the consumer (ANPR-H�-OAR-2008-0318; FRL 8694-2). With an RPE of 1.75 the cost to the original equipment manufacturer would be just over $60. TABLE 7.10 Estimates of Replacement Costs for Transmission Technologies Relative to 2007 4-Speed Automatic Transmissions $Cost $RPE $Cost $RPE Transmission Type (EEA, 2007) (EEA, 2007) (Martec, 2008) (Martec, 2008) 5-speed automatic 133 200 — — 6-speed automatic 133 205 215 323 7-speed automatic 170 255 — — 8-speed automatic — — 425 638 DCT (dry clutch, 250 N-m) — — 300 450 DCT (wet clutch, 350 N-m) 140 210 400 600 CVT (engine <2.8 liter) 160 240 — — CVT (engine >2.8 liter) 253 380 — — NOTE: RPE values were determined using a cost multiplier of 1.5.

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115 NON-ENGINE TECHNOLOGIES in mass (material substitution), improving aerodynamics, over the next 5 to 10 years appears to be within reach for the or switching to low-rolling-resistance tires. More substan- typical automobile, considering the current baseline. tive changes require longer-term coordination with the PDP Transmission technology has significantly improved and, because reengineering and integration with other subsystems like other vehicle technologies, shows a similar curve of are necessary. This could include resizing the power train/ diminishing returns. Planetary-based automatic transmis- transmission or aggressively reducing mass (e.g., changing sions can have five, six, seven and eight speeds, but with the body structure). Substantive changes like this will take incremental costs increasing faster than their impact on fuel 4 to 8 years to adopt. The cost estimates provided in this consumption. Continuously variable transmissions have been chapter all assume coordination with the PDP to help contain available on the market for a number of years, but their rate costs and achieve maximum impact. of implementation seems to have flattened out, suggesting Two important technologies impacting fuel consumption that future new implementations will be limited in number. addressed in this chapter are light-weighting and transmis- DCTs are in production by some vehicle OEMs (e.g., VW/ sions. Light-weighting has almost unlimited potential because Audi DSG), and new DCT production capacity has been an- vehicles can be made very light with exotic materials, albeit at nounced by other vehicle OEMs and suppliers. It is therefore potentially high cost. The incremental cost to reduce a pound expected that the predominant trend in transmission design of mass from a vehicle tends to increase as the total amount of will be conversion both to 6- to 8-speed planetary-based reduced mass increases, leading to a curve with diminishing automatics and to DCT automated manuals, with CVTs returns. About 10 percent of vehicle mass can be eliminated remaining a niche application. Because of the close linkage at a cost of roughly $700 (or about $2.00/lb; see Table 7.11). between the effects of fuel-consumption-reducing engine If the aggressiveness to reduce mass increases much beyond technologies and those of transmission technologies, the 10 percent, it is necessary to begin addressing body structure present study has considered primarily the combined effect of design (such as considering an aluminum-intensive car), and engines and transmission combinations rather than potential the cost per pound increases. A 10 percent reduction in mass separate effects. TABLE 7.11 Summary of the Committee’s Findings on the Costs and Impacts of Technologies for Reducing Light-Duty Vehicle Fuel Consumption Impact on Fuel Fuel Consumption Consumption Technology Description and Approximate Manufacturing Cost (%) Comments Mass reduction 1% (36 lb); $46-$55 0.25 Material substitution (assume 3,600- 5% (180 lb); $270-$324 Material substitution 3-3.5a pound vehicle) 10% (360 lb); $648-$778 Aggressive material substitution 6-7a 20% (720 lb); $1,600+ 11-13a Redesigned body with aluminum and composite- intensive structures Transmission Five-speed automatic transmissions; $133 2-3 Can also improve vehicle performance Six-speed automatic transmissions; $133-$215 3-5 Can also improve vehicle performance Seven-speed automatic transmissions; $170-$300 5-7 Can also improve vehicle performance Eight-speed automatic transmissions; $425 6-8 Can also improve vehicle performance Dual-clutch automated (DCT) manual transmissions 6-9 DCTs have replaced original automated manual (6/7 speed); $300 (dry clutch), –$14-$400 (wet transmissions clutch <350 N-m) Continuously variable transmissions; $150 (<2.8 L), 1-7 Possible engine noise; not applicable to large engines $263 (>2.8 L) Aerodynamics 5 to 10% reduction in Cd (coefficient of drag); 1-2 Wheel well and underbody covers, body shape, $40-$50 mirrors, etc.; bigger impact on highway drive cycle Rolling resistance Low-rolling-resistance tires; approximately $10 Stopping distance and durability can be compromised 1-2b apiece ($30-$40) with inferior materials; optimal materials drive up costs Tire-inflation monitor; becoming standard equipment 0.7 Depends on monitor settings and driver behavior Low-drag brakes; becoming standard equipment 1 Most cars equipped already today Electrical accessories HVAC—variable stroke, increased efficiency 3-4 Current FTP does not capture benefit (benefits reduced (humidity control, paint, glass, etc.); $70-$90 to 0.5-1.5% within Table 9.1) Electric and electric-hydraulic power steering; 1-5 Electric for small cars, electric-hydraulic for bigger $70-$120 cars—benefits for the FTP are smaller (1-3%). aWith resized power train. bThree percent may be feasible with resized power train.

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116 ASSESSMENT OF FUEL ECONOMY TECHNOLOGIES FOR LIGHT-DUTY VEHICLES Accessories are also being introduced to new vehicles a significant increase in costs. The uncertainty and instabil- to reduce the power load on the engine. Higher-efficiency ity of commodity prices (e.g., for carbon fiber, resins, and air-conditioning systems are available that more optimally aluminum versus steel) increase the risk to the vehicle manu- match cooling with occupant comfort. This includes, for facturer of adopting these new materials. example, humidity control, air recirculation, and increased Finding 7.3: Transmissions. Another promising technology compressor efficiency using a variable-stroke compressor. Electric and electric-hydraulic power steering also reduces for reducing vehicle fuel consumption is transmissions with the load on the engine by demanding power (electric) only an increased ratio spread between the low and the high gears when the operator turns the wheel, whereas the older technol- (e.g., 6-8 speeds) and dual-clutch transmissions that elimi- ogy relied on hydraulic power supplied by the engine all the nate torque converters. time. An important motivating factor affecting the introduc- Finding 7.4: Lower-energy-loss accessories. A collec- tion of these accessories is whether or not their impact is measured during the official CAFE certification tests. The tion of relatively low-cost vehicle technologies can have a certification test currently does not take the air conditioner positive impact on reducing fuel consumption. Low-rolling- into account, and so there is little motivation to improve its resistance tires, improvements to vehicle aerodynamics, and efficiency and incur added cost; however, this situation may electric power steering can all cost less than $200 in total change with newly proposed test procedures. while reducing fuel consumption by about 10 percent, if Estimates for these technologies and several others are HVAC is included as a component of real-world driving. summarized in Table 7.11. The fuel consumption estimates Other technologies that can yield incremental reductions assume ideal conditions, and there are important interaction in fuel consumption are increased HVAC compressor effi- effects among different technologies. Generally, it is not pos- ciency, ultraviolet filtering, glazing, and cool/reflecting sible to apply two or more of the technologies in Table 7.11 paints, but these technologies are not currently pursued and algebraically add the impacts on fuel consumption. The very aggressively because they are not taken account of typical impact from multiple technologies will be less than in the official CAFE certification tests. It would take more the sum of their individual fuel consumption estimates. than the addition of HVAC in one of the five test schedules used to report fuel economy on the vehicle sticker to have a significant impact on the penetration of these technologies. FINDINGS Finding 7.1: Refresh/redesign. With respect to reducing fuel REFERENCES consumption, recognition of product development process Automotive News. 2008. A big fuel saver: Easy rolling tires (but watch timing is important for minimizing the cost of implement- braking). July 21. ing many new vehicle technologies. Only relatively modest Barrand, J., and J. Bokar. Reducing tire rolling resistance to save fuel c hanges can be made when vehicles are restyled, and and lower emissions. SAE Paper 2008-01-0154. SAE International, secondary benefits from mass reduction are unlikely. The Warrendale, Pa. reengineering or redesign phases of product development Bull, M. 2008. Efficacy, cost, and applicability of lightweight structures to fuel economy. Presentation to the Committee for the Assessment of offer the greatest opportunity for implementing new fuel- Technologies for Improving Light-Duty Vehicle Fuel Economy, June 3, saving technologies, and this can occur from 4 to 8 years Washington, D.C. after initial introduction. Significant changes to power train Carpenter, Jr., J., U.S. Department of Energy, Washington, D.C. 2008. Chal - and vehicle structure and materials can be made more easily lenges to automotive composites. Presentation to American Chemistry at this time. Council, Plastics Division, Arlington, Virginia, May 20. Cheah, L., C. Evans, A. Bandivadekar, and J.B. Heywood. 2007. Factor of Two: Halving the Fuel Consumption of New U.S. Automobiles by Finding 7.2: Mass reduction. 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Update for Advanced (by, say, 5 to 10 percent) will require system solutions (as Technologies to Improve Fuel Economy of Light Duty Vehicles—Final Report. Prepared for U.S. Department of Energy. October. opposed to material substitution solutions). Achieving a mass EPA (U.S. Environmental Protection Agency). 2008. EPA Staff Techni- reduction of greater than 10 percent (as high as 20 percent) cal Report: Cost and Effectiveness Estimates of Technologies Used will require a significant change in vehicle design (such as to Reduce Light-Duty Vehicle Carbon Dioxide Emissions. EPA420- a shift to an aluminum-intensive body or aggressive use of R-08-008. Ann Arbor, Mich. other higher-cost materials like carbon fiber) and will incur Forbes. 2008. Automakers’ natural appeal, Forbes Magazine, September 26.

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117 NON-ENGINE TECHNOLOGIES Gessat, J. 2007. Electrically powered hydraulic steering systems for light Martec Group, Inc. 2008. Variable Costs of Fuel Economy Technologies. commercial vehicles. SAE Paper 2007-01-4197. SAE International, Prepared for Alliance of Automobile Manufacturers. June 1; amended Warrendale, Pa. September 26 and December 10. Goodyear Tire & Rubber Company. 2009. Letter from Donald Stanley, NRC (National Research Council). 2002. Effectiveness and Impact of Cor- Vice President, Product �uality and Plant Technology, April 13, 2009; porate Average Fuel Economy (CAFE) Standards. Washington, D.C.: e-mail exchanges with Donald Stanley, January, 28, 2009, and Febru- National Academy Press. ary 25, 2009. NRC. 2006. Tires and Passenger Vehicle Fuel Economy: Informing Con- Heremans, J.P., V. Jovovic, E.S. Toberer, A. Saramat, K. Kurosaki, A. sumers, Improving Performance—Special Report 286. Washington, Charoenphakdee, S. Yamanaka, and G.J. Snyder. 2008. Enhancement of D.C.: The National Academies Press. thermoelectric efficiency in PbTe by distortion of the electronic density Pagerit, S., A. Rousseau, and P. Sharer. 2006. Fuel economy sensitivity to of states. Science 321:554. vehicle mass for advanced vehicle powertrains. SAE Paper 2006-01- Hussain, �., C. Maranville, and D. Brigham. 2009. Thermoelectric exhaust 0665. SAE International, Warrendale, Pa. heat recovery for hybrid vehicles. SAE Paper 2009-01-1327. SAE Inter- Powers, W. 2000. Automotive materials in the 21st century. Advanced national, Warrendale, Pa. Materials and Processes, May. IBIS Associates. 2008. Benefit Analysis: Use of Aluminum Structures in Ricardo, Inc. 2007. Impact of Vehicle Weight Reduction on Fuel Economy Conjunction with Alternative Power Train Technologies in Automobiles. for Various Vehicle Architectures. Prepared for the Aluminum Associa- IBIS, Waltham, Mass. tion, Inc. Kolwich, G. 2010. Light-Duty Technology Cost Analysis—Report on Rugh, J.P., L. Chaney, J. Lusbader, J. Meyeer, M. Rustagi, K. Olson, and R. Additional Case Studies. Prepared for U.S. Environmental Protection Kogler. 2007. Reduction in vehicle temperatures and fuel use from cabin Agency. FEV, Inc., Auburn Hills, Mich. ventilation, solar-reflective paint, and a new solar-reflective glazing. SAE Paper 2007-01-1194. SAE International, Warrendale, Pa.