An experimental study on methanol-gasoline and gasoline-methanol dual-fuel spark ignition (DFSI) combustions for knock suppression and higher engine efficiency was conducted with a high compression ratio gasoline engine. The methanol gasoline DFSI was organized using a port fuel injection (PFI) of methanol and a direct injection (DI) of gasoline

while the gasoline-methanol DFSI was organized by gasoline PFI and methanol DI. The tested engine was naturally aspirated and operated at stoichiometric condition. In the test

the amount of methanol injection was varied from 0 to 100%. The effects of these two injection modes on knock-limit extension

fuel economy

and PM reduction were investigated. The test results show that both the methanol-gasoline DFSI and gasoline-methanol DFSI are promising approaches of using alternative alcohol fuels in practical gasoline engines with significant improvement in engine efficiency and knock suppression. The gasoline - methanol DFSI exhibits better in anti-knock performance and PM reduction than the methanol-gasoline DFSI.