Fuel Evaporation and the High Speed Knock Phenomenon of Methanol-Gasoline Blended Fuels

The results of an investigation into intake system fuel evaporation are used to study the influence of engine speed on fuel anti-knock performance. It is found that, while adding methanol to gasoline causes dramatic cooling at low engine speeds, this relative effect is lost at higher speeds, primarily due to lower residence times. At low speeds, the cooling inhibits knock for methanol-gasoline blends. However, at high speeds, these blends are found to lose this relative advantage, removing the knock inhibition provided by cooling, and this facilitates knocking at high speeds.