The Effect of Increasing Fuel Volatility on Exhaust Emissions

Vehicle tests showed that exhaust HC and CO were significantly increased with a high volatility (12.5 psi Reid vapor pressure) Indolene plus butane blended fuel when compared to Indolene (9.0 psi RVP) fuel. The HC and CO increases were greater for a vehicle without closed-loop fuel control than for three closed-loop vehicles. Testing indicated that the exhaust emissions increases may have resulted from the higher loading of the evaporative canister with the high RVP fuel. Exhaust NO_X emissions were not affected by the change in fuel volatility.