Labels:text | screenshot | font | black and white | document OCR: GAS ENGINE DISCUSSION The "gas" engine is more correctly called the spark ignition or S.I. engine because the burning of the fuel air mixture drawn into the cylinder is initiated by a spark, which occurs at about the top of the compression stroke. The exact timing depends on several factors, including the engine speed, throttle setting, fuel-air ratio and temperature to name a few. The spark ignites the fuel air mixture; a flame front then propagates rapidly (and silently) across the combustion chamber, heating the gas and thereby raising the pressure in the cylinder. The efficiency and maximum power output of an internal combustion engine are fundamentally limited by the compression ratio. Unfortunately, if the compression ratio of a gas engine is raised too much, the fuel air mixture wil ...
