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The impact of market-fuel variations on the HCCI operating range was measured in a 2.3L four-cylinder engine, modified for single-cylinder operation. HCCI combustion was achieved through the use of residual trapping. Variable cam phasing was used to maximize the load range at each speed. Test fuels were blended to cover the range of variation in select commercial fuel properties. Within experimental measurement error, there was no change in the low-load limit among the test fuels. At the high-load limit, some small fuel effects on the operating range were observed; however, the observed trends were not consistent across all the speeds studied.

The fuel effects on HCCI operation in a spark assisted direct injection gasoline engine are assessed. The low load limit has been extended with a pilot fuel injection during the negative valve overlap (NVO) period. The fuel matrix consists of hydrocarbon fuels and various ethanol blends and a butanol blend, plus fuels with added ignition improvers. The hydrocarbon fuels and the butanol blend do not significantly alter the high or the low limits of operation. The HCCI operation appears to be controlled more by the thermal environment than by the fuel properties. For E85, the engine behavior depends on the extent that the heat release from the pilot injected fuel in the NVO period compensates for the evaporative cooling of the fuel.