Effects of Gasoline Properties on Acceleration Performance of Commercial Vehicles

Under hot transient conditions, the effects of gasoline properties, such as the research octane number (RON), the motor octane number (MON) and types of components on acceleration performance were investigated using four ‘Premium Gasoline Required Vehicles’ which are Japanese commercial vehicles equipped with knock sensors (KSs) and an electronic control unit (ECU) to prevent the engines from knocking. Regarding the fuel, two series of fuels were used. One of them {Primary Reference Fuel Series (PRF series)} was prepared to investigate the effectiveness of the octane number of PRF (ON). The other {Components Series (COMP series)} was prepared to investigate the effects of fuel components on the same. Fuels in the COMP series had almost the same RON level, which was almost equal to 90. In the PRF series, the acceleration performance of all vehicles were improved as ON increased. However, the effect of ON regarding the acceleration performance differed among vehicles because of the algorithm in the ECU of the vehicle. Moreover, as ON decreased, hydrocarbons (HC) and carbon monoxide (CO) emissions during acceleration increased while nitrogen oxide (NOx) emission decreased. In the COMP series, acceleration performance of some vehicles improved when higher types of MON fuels containing MTBE, TAME or cycloparaffins were used. Estimated road octane number (ERON), calculated by the weighted average of RON and MON, was a good index to express the antiknock performance of a fuel rather than RON or MON in some vehicles. Fuels with paraffinic oxygenates decreased HC and CO emissions in some vehicles. Heavy components in fuels not only increased HC and CO emissions but also deteriorated acceleration performance due to their poor vaporization.