and 0.43 grams per mile NO These levels were achieved by improving the configuration of the auxiliary combustion chamber and the air-fuel control pattern. No EGR or exhaust-treatment devices were used. The emissions are not especially sensitive to variations in airfuel ratio. Thus the required performance of the double carburetor system is no more demanding than current requirements. The two throttle plates are linked mechanically. operating mode. The mean air-fuel ratio varies with The new cylinder head is about the same height as a conventional head. The new head, intake, and carburetor on the modified Vega fit comfortably into the engine compartment. 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. There is a slight loss in power for the same engine displacement due to leaner operation and decreased volumetric efficiency. Fuel economy is essentially unchanged. There are no driveability penalties. X Development of the Honda CVCC engine to achieve lower NO emissions is continuing. The effects of EGR and modifications to the basic combustion process are being examined. 3.10 Effect of Emission-Control Devices on Vehicle Performance, Some of the emission-control devices and techniques required to meet the 1976 emission standards have a profound effect on at least three areas of vehicle performance: acceleration capability, fuel economy, and driveability. There is also some concern that poor performance of such cars will make them unsafe in certain circumstances, for example, if the vehicle stalls when accelerating into fast-moving 94-492 0-73-pt. 118 · 62 traffic. The customer is sensitive to these characteristics which affect both his pocketbook and his attitude toward any particular vehicle. Traditionally this area has been one in which customer complaints and warranty returns have been especially prevalent. It is therefore not surprising that manufacturers have registered great concern in the past about the adverse effects of emission control devices By the same token, however, the market place imposes considerable inherent motivation for manufacturers to devote great attention to product improvement in these areas. The comments that follow in this section refer primarily to vehicles equipped with the dual-catalyst emission-control system. Χ X In general, vehicle acceleration capability is reduced by control measures applied for control of all three pollutants (HC, CO, and NO); however, NO control measures which reduce combustion temperature have the most serious deleterious effects. Reductions in compression ratio to enable use of lower-octane gasoline resulted in acceleration penalties, as did the minimization of enrichment techniques formerly provided specifically for rapid acceleration capability. In addition, the use of EGR to reduce combustion temperatures and thereby inhibit NO production imposes a severe acceleration penalty. X Losses in fuel economy accompany most of these losses in acceleration capability and are aggravated by countermeasures taken to overcome deficiencies in acceleration capability and driveability. Many of the smaller engines have been dropped in the various car lines The use of a larger displacement engine results in a fuel economy penalty for both city and open-highway driving. When EGR is used to control NO emissions, the mixture must be enriched to retain adequate driveability, causing drastic reductions in fuel economy. X The most troublesome of numerous driveability problems is the cold-start problem. The quick choke action and subsequent lean mixtures required to minimize HC and CO emissions introduce problems with engine stalls and unsatisfactory drive-away during warm-up. and spark retard cause such problems as lack of response, die-outs, and hesitation on acceleration. EGR In its January 1, 1972, report, the CMVE concluded that all three areas of vehicle performance discussed above would be adversely affected by the 1975 emission-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. All manufacturers anticipated losses in driveability, in some cases indicated to be severe. Anticipated increases in fuel consumption ranged from 5 to 15 percent for standard sized cars up to 20 to 30 percent for small cars, again over 1971 levels. Much of the deterioration in performance was anticipated to come with the introduction of NO requirements in 1973, and early reports on performance of the X new models have confirmed this. During 1972, the CMVE has received reports on both the 1975 and 1976 emission-control system progress. While manufacturers are still concerned with performance, particularly fuel consumption, the concern over vehicle driveability has diminished. No substantial new acceleration, fuel economy, or driveability problems are introduced with the 1976 emission-control systems compared with the 1975 systems. At the same time, considerable progress has been made in finding solutions to problems that appeared to be very serious one year ago. It seems likely that competitive pressures will result in further improvements and improved reliability in these performance areas. The effort required is essentially engineering development based on extensive field experience with these new systems. The major long-term concern should be the continuing fuel economy penalty which results from the decreased compression ratio to allow the use of unleaded fuels, compounded by the use of EGR to control NO emissions to very low levels, and aggravated by the increased engine sizes introduced to compensate for the loss in performance. X 3.11 Alternative Fuels One approach to reduce emissions from conventional engines is the use of alternative fuels. The use of liquefied natural gas (LNG), liquefied petroleum gas (LPG), hydrogen, and alcohols have been considered by the Committee. 3.11.1 Liquefied Natural Gas and Liquefied Petroleum Gas X Both industry and governmental groups have evaluated natural gas and propane (LPG) to determine their capability in reducing emissions from automobiles. One engine manufacturer showed that emission levels approaching the 1975-76 standards can be achieved, but exhaust gas recirculation is still required to reduce NO formation to the 1975-76 standard. There is an 8 percent loss in peak engine power (350 cu. in. 1970 engine) from gasoline when using LPG and a 15 percent loss using natural gas. There is a substantial loss in fuel economy (30 percent), and driveability is impaired. The use of LPG for starting and warm-up in a dual-fuel car using gasoline for conventional operation was attempted. Cold-start emissions are decreased. On an experimental natural-gas 6-cylinder engine sized for bus operation, another manufacturer showed that the use of compressed or liquefied natural gas would produce emissions which would meet 1975 standards. The 1976 NO standard could be met only with EGR, a catalytic after-burner, and a great reduction in performance. sions were odorless and there was no particulate matter present. X The emis There are over 5,000 cars converted to run on gaseous fuels in the Los Angeles basin where gas supplies and liquid systems have been joined together to provide the gaseous fuels to the car operators. Emissions are cleaner, maintenance is reduced, but a heavy bulky tank is required to hold the gaseous fuel. 3.11.2 Status of Liquefied-Gas Substitutes for Gasoline The CMVE has investigated the technical problems and economic factors involved in supplying natural gas and LPG. It is possible to modify the petroleum refining process so that LPG can be substituted for gasoline for motor vehicles. The original capital costs would be in the $50 billion range. about twice as much as gasoline presently costs. Also, there is a serious net loss of energy in changing from gasoline to LPG. The percentage of crude oil consumed in the processing operations would increase from about 4 percent to about 14 percent. This would be an unrecoverable waste of natural resources. The fuel costs to the customer would be There is not enough LPG, LNG, or Synthetic Natural Gas (SNG) currently available to be significant if conversion were desired now. A three-year lead-time for making changes for supplying these alternative fuels is a minimum. 3.11.3 Hydrogen Hydrogen gas has three properties which, when taken together, give it a unique potential as a vehicular fuel. First, since there is no carbon in the fuel, the problems of unburned hydrocarbons and of No after-burner, catalyst, or other carbon monoxide do not exist. secondary reaction vessels are needed. Second, the flammability limits of hydrogen are extremely wide. The volume percentage of hydrogen in air can range over a factor of 19 |