The objective of this investigation is to compare the transient firing behavior of a spark-ignition engine fueled with methanol, liquefied petroleum gas (LPG), and methanol/LPG, respectively, during cold start by means of a cycle-by-cycle control strategy. The experimental results showed that the ambient temperature affects the methanol-fueled engine reliable cold start the most significantly, and the amount of methanol injected per cycle takes the second place. When the ambient temperature is below 16, the methanol-fueled engine can not be started reliably without auxiliary start-aids even at a large amount of methanol injected per cycle under low injection pressure. The amount of fuel injected per cycle affects the LPG- and the methanol/LPG-fueled engine cold start reliability significantly. A proper amount of fuel injected per cycle can ensure reliable start of the LPG- and the methanol/LPG-fueled engine. At the same injection timing of LPG and methanol, the LPG-fueled engine may realize the ideal firing of the next cycle combustion after fuel injection, and the firing of the methanol-fueled engine is one cycle later than that of the LPG-fueled engine. If the injection timings of methanol and LPG are controlled reasonably at cold start, the methanol- and the methanol/LPG-fueled engine may realize the ideal next cycle firing after fuel injection.
