The effects of temperature and fuel volatility on vehicle evaporative emissions

Report no. 90/51: Matched pairs of European vehicles with and without carbon canister evaporative emission control systems have been tested to establish gasoline evaporative emissions, including running losses.Measurements were made over a range of ambient temperatures, fuel volatilities and different driving patterns.

The uncontrolled vehicles exhibited gasoline vapour emissions which increase progressively with ambient temperature and fuel volatility. A 1°C change in ambient temperature was found to have the same effect on evaporative emissions as a 3.8 kPa change infuel RVP Carbon canisters were found to provide effective control of gasoline vapour emissions, capable of reducing total daily emissions by around 95%.

Large reductions in benzene emissions were achieved by the canisters, in line with the total emissions.Reducing fuel volatility had no significant effect on emissions from the canister equipped vehicles.