Report by the Committee on Motor Vehicle Emissions (1973) / Chapter Skim
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3 Potential of Spark-Ignition Internal-Combustion Engines Passing Emission Certification for 1975 and 1976
3 Potential of Spark-Ignition Internal-Combustion Engines Passing Emission Certification for 1975 and 1976
Pages 22-68
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From page 22... ...
S and foreign manufacturers are currently assembling and testing fleets of vehicles equipped with the complete system to evaluate different promising catalyst materials and to obtain data on system durability before final production designs are frozen.
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From page 23... ...
For same manufacturers, the current fleet tests represent the first extensive evaluation of the complete engine emission controls with the best oxidation catalyst materials now available. Data obtained fray same of these manufacturers' fleets are shown in Table 3-1.
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of .,l ~ ` o · A Ad c~ cam of A · · · · c~ c~ c~ c~ ~ LO om ~ ~ ~ e · · · ~ ~ O O ~ C~ ~ _ C~1 C~ )
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From page 25... ...
have completed 50,000mile durability testing and met the standards at every test throughout the test period. The Wankel engine with a thermal reactor has achieved emission levels below the 1975 standards in a compact car.
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From page 26... ...
results in a large fuel-economy penalty, severe driveability problems with attendant safety hazards, and an increase in engine HO and CO emissions. It is not practical at this stage to achieve NO -emission levels approaching 0.4 g/mile with EGR alone in a conventional engine.
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From page 27... ...
rich mixture must be provided during cold starts. The excess fuel is not fully burned in the combustion chamber, and the cold engine thus emits high levels of hydrocarbons and carbon monoxide.
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From page 28... ...
3.3.3 Carburetors The precise metering of the fuel and air to automotive engines has become much more important in recent years because the mixture ratio is a critical parameter affecting the exhaust composition and the functioning of exhaust-treating devices. Most 1975-76 model carburetors have been redesigned to achieve better air-fuel ratio control and maintain good co Id - s tart pert ormance o f the engine .
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From page 29... ...
EFI systems can respond quickly to changes in operating conditions and are therefore able to provide satisfactory control of air-fuel ratio under transient conditions. However, contacts made with carburetor manufacturers, automobile manufacturers, and producers of electronic fuel injection equipment indicate that current EFI systems do not provide substantial improvement in air-fuel control over the advanced-design carburetors operated under steady conditions.
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From page 30... ...
3 . 6 Potential for Engine Emis sion Reduction The methods of emission reduction discussed so far have been engine modifications that reduce emissions from the bare engine, i.e., before after-trea~ment devices such as catalysts and thermal reactors.
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From page 31... ...
engine emissions, rich carburetion 1.5 25 1.5 ( ) 1972 C7S-C test procedure (b )
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From page 32... ...
The further reduction of emissions in conventional engines must be achieved with exhaust treatment, such as catalysts or thermal reactors . 3.4 Catalysts The control system for 1976 on which most development effort has been concentrated uses two catalyst beds to clean up the engine emissions before exhaust to the atmosphere.
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From page 33... ...
~9 LL In Cal A: C)
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From page 34... ...
~ The oxidation catalysts used in these dual-catalyst systems are the catalysts now being developed for 1975 model year vehicles. These consist of noble metals (platinum and/or palladium)
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From page 35... ...
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From page 36... ...
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 ~ 1 ~ ~ 1 1 1 1 to 1 ~ ~ 1 1 V 1 aL1 ~1 1 ~1 1 _I ~1 1 1 ~ ~ <1)
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From page 37... ...
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From page 38... ...
The results of the most promising durability tests of some dualcatalyst vehicles are summarized in Table 3-4. Emissions are shown as a function of mileage.
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From page 41... ...
c, e~d erl U
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From page 42... ...
It is not known how severely these contaminant levels will affect the activity of the different NOX catalysts now being evaluated. Laboratory tests on a noble metal NOX catalyst which contained platinum and other metals showed lead poisoning of magnitude comparable to that observed with platinum oxidation catalysts.
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From page 43... ...
Ammonia formation increases with carbon monoxide level in exhaust mixtures. Thus, whereas the air-fuel mixture must be slightly fuel-rich to provide net reducing conditions at the NO -catalyst bed, too great a CO level leads to excess ammonia formation and results in increased concentrations of NO in the exhaust.
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From page 44... ...
The width of this window has been found to be only + .1 air-fuel ratio, thus requiring an overall control of air-fuel ratio to within less than + 1 percent. Lean-side deviations from this window result in a drastic loss of NOx conversions; richside deviations lead to considerable loss of HO and CO oxidation efficiencies and increased ammonia formation.
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From page 45... ...
Because the oxygen sensor is an electrical transducer, it is particularly well suited for adaptation to the electronic circuitry of the EFI control module. Also, fuel-injection systems provide quicker response to error signals than do carburetors.
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From page 46... ...
This system is more complex than the three-way catalyst approach since an air pump is required to supply secondary air upstream of the oxidation catalyst, and air must be diverted to upstream of the NOx-reduction catalyst during the cold-start portion of the test. Again, the elf mination of e~aust-gas composition excursions outside the desirable operating window of the catalysts would be expected to improve catalyst life, and there is a better chance to develop separate oxidation and reduction catalysts by a given time than to find a three-way catalyst adequate to the job.
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From page 48... ...
There have been two basic versions of systems using a thermal reactor only: fuel -rich and fuel- lean sys tems . The fuel-rich system results in less NOX formation, but only at the expense of substantially poorer fuel economy.
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From page 49... ...
Another reactor-plus-catalyst approach is being developed by Questor. Their system consists of a small-volume thermal reactor bolted onto the cylinder head, in which partial oxidation of engine HC and CO emissions occurs, followed by an Inconel 601 screen NO -reduction catalyst, followed by a final oxidizing thermal reactor.
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From page 50... ...
With its inherently high exhaust temperatures and its exhaust ports all adjacent, the Wankel engine is particularly well suited to emission control by a thermal reactorCurrent production rotary engines on compact cars operated with~rich carburetor settings and thermal reactors have been developed to meet the 1975 standards with NO x levels of about 1 gram per mile. However, the fuel-economy penalty compared with a current equivalent piston engine is about 30 percent.
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From page 51... ...
Marl up a · d \9 ~ 1 C: ¢ ~ o o a, in U]
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From page 52... ...
The best results achieved with oxidation catalysts and rotary engines are shown in Table 3-8. Levels approaching the 1975 standards for BC and CO have been achieved at low mileage with a compact car.
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From page 54... ...
* Oxidation catalys t 22 and air pump (Best Effort)
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From page 55... ...
The Ford engine required two catalys t changes and frequent maintenance. The Texaco engine used three oxidation catalysts in series to achieve the required HO and CO emission control.
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From page 56... ...
23 O 31 TCPd 10,000 0.77 1.90 0.38 Emission controls include oxidation catalyst, EGR, throttling at light load.
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From page 57... ...
One of the advantages of the stratified-charge engine is excellent fuel economy relative to conventional engines, particularly when emissions controls are applied. The original version of the stratifiedcharge L-141 engine developed for optimum fuel economy showed a 30 percent fuel economy gain over the conventional carbureted engine.
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From page 58... ...
o As o 0 o o o o to 1 a)
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From page 59... ...
Low-mileage emissions data are given in Table 3-11 for 54 Honda vehicles and two modified GM Vegas. All these cars met the 1975 standards without EGR or exhaust treatment, and Honda has expressed confidence that larger engines using the CVCC approach could also be made to meet 1975 standards without a catalyst.
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From page 60... ...
Cal Cal C: b0 a)
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From page 61... ...
c,: o is lo a)
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From page 62... ...
The engine can operate on regular leaded gasoline; durability testing has been on unleaded gasoline to simulate fuel anticipated in the United States in 1975. The effects on vehicle performance of the CVCC system are small.
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From page 63... ...
Reductions in compression ratio to enable use of l~wer-octane gasoline resulted in acceleration penalties, as did the minimization of enrichment techniques formerly provided specifi cally for rapid acceleration capability. In addition, the use of EGR to reduce combustion temperatures and thereby inhibit NOx production imposes a severe acceleration penalty.
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From page 64... ...
In its January 1, 1972, report, the COVE concluded that all three areas of vehicle performance discussed above would be adversely affected by the 1975 em~ssion-control systems. Information received from manufacturers indicated losses in acceleration capability ranging from a minimum of 5 percent to a maximum of 20 percent over 1971 levels.
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From page 65... ...
, hydrogen, and alcohols have been considered by the Committee. 3.11.1 Liquefied Natural Gas and Liquefied Petroleum Gas Both industry and gove~-~ental groups have evaluated natural gas and propane (LPG)
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From page 66... ...
11. 3 Hydrogen Hydrogen gas has three properties which, when taken together, give it a unique potential as a vehicular fuel.
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From page 67... ...
When natural gas approaches exhaustion, the cheapest way of making hydrogen gas will be to use coal as the base material. When the price of coal becomes too high, hydrogen can be made by heating or electrolyzing water.
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From page 68... ...
g., methyl alcohol is widely used as a racing fuel. Methanol has the advantage of providing a lower combustion temperature, reducing the NOx emissions, and it also has lower lean misfire limits than gasoline, thus reducing HO, CO, and NOx emissions while maintaining a satisfactory driveability.
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