As a first attempt to assess the scope for reducing the emissions from gasoline fuelled vehicles in the European market via fuel changes, an experimental scouting programme has been conducted to examine the effects of fuel composition and properties on both regulated emissions and detailed exhaust gas composition. This 4 fuels/4 vehicles programme involved exhaust emission tests on a chassis dynamometer, and was carried out mainly on non-catalyst vehicles, using two commercial gasolines and two (“reformulated”) test gasolines representing “intermediate” and “extreme” changes of the base gasoline design. The fuel characterization includes analysis by hydrocarbon type and carbon number; the exhaust analysis comprises both regulated emissions and hydrocarbon speciation measurements.
In the case of regulated emissions, the fuel effects are, as expected, relatively small in comparison with the effect of installing exhaust catalysts. Nevertheless, significant emission benefits are achieved via the fuel changes relative to one of the commercial gasolines. Interestingly, however, relatively modest changes prove to be sufficient to produce these benefits, and further extreme reformulation does not promote additional emissions reductions. Moreover, the second commercial gasoline gives essentially the same reductions in total hydrocarbon and carbon monoxide (but not nitrogen oxides) emissions as the two “reformulated” fuels.
Exhaust gas hydrocarbon speciation profiles for a given fuel are very similar for different cars and different (i.e cold and hot ) parts of the driving cycle. The detailed hydrocarbon composition of the exhaust gas is dominated by the gasoline composition, with the exception of the exhaust olefins which are as dependent on the paraffins as on the olefin content of the fuel.
A much larger follow-up programme is now underway in which the fuel effects on emissions are being investigated systematically for both catalyst and non-catalyst cars via independent variation of individual fuel parameters.