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In order to clarify the effect of each gasoline component on engine performance during warm-up, changes in the air-fuel ratio and quantity of wall flow (liquid gasoline on the induction port) were measured using ordinary gasolines and model gasolines consisting of a blend of several hydrocarbons and MTBE (methyl-tertiary-butyl-ether). The unburned air-fuel mixture in a combustion chamber was sampled via a solenoid valve and analyzed by gas chromatography to investigate the vaporization rate of each component. The results show that MTBE has an important effect on driveability because it contains oxygen and easily vaporizes, resulting in a lean mixture in the transient state. The popular driveability index, T50 (50% distillation temperature), does not provide an adequate means of evaluating MTBE-blended gasoline.

Valve deposits in gasoline engines increase with time, absorbing fuel during acceleration and releasing fuel during deceleration. Valve deposits insulate the heat release from the cylinder and this phenomenon is the cause of bad fuel vaporization. In this way, the deposits greatly affect the driveability and exhaust emissions. Using a 3.OL MPI(Multipoint Injection) engine, we measured the quantity of fuel that deposits at the intake port, and the throttle response (using a wall-flow meter made by Nissan Motor Co.1), 2) to study the deposits effect on driveability and exhaust emissions at a low temperature. The deposits were formed on the intake valve surface (about 8.0 on the CRC deposit rating scale) through 200 hours of laboratory engine stand operation. At low temperature, C9 and C10 hydrocarbons tend to stick to the intake port surface and intake valve as “wall-flow”; this is one cause of bad driveability.

This study evaluates the influence of speciated emissions on ozone reactivity using the values of Maximum Incremental Reactivity published by the California Air Resources Board in September 1990. To evaluate the influence of fuels and vehicle specifications on speciated emissions and ozone reactivity, three different fuels (gasoline, reformulated gasoline, and methanol (M85)) were used. Hydrocarbon species were measured using three types of gas chromatographs. Aldehydes were collected in a dry cartridge and measured by High Performance Liquid Chromatograhpy (HPLC). Alcohols were collected using impingers and measured by a gas chromatograph. In the case of gasoline, as Non-methane Organic Gas (NMOG) is reduced, the proportion of speciated emissions with high ozone reactivity decreases, and this tends to lower Ozone Forming Potential (OFP). In the case of reformulated gasoline, OFP does not decrease, but Non-methane Hydrocarbons (NMHC) do as NMOG is reduced.