Knock suppression in spark-ignition engine by using methanol injection

A methanol injection system has been built and installed on a CFR SI engine. Methanol was injected into the intake manifold to mix with the indolene-air charge coming from the carburetor.;It has been found that the injection of methanol is a very effective method for suppressing knock in gasoline engines. The evaporative cooling effect of the inlet charge and the impeding effect on the preknock reactions in the end gas are the two main factors that caused the knock in the engine to be suppressed.;The results of the experiments show that under engine condition of this study, for indolene with methanol injection, the effect of mean cylinder pressure and mean end gas temperature on the end gas autoignition delay period can be expressed by the inverse form of the Arrhenius relationship: t;Also, knock limited compression ratio (KLCR) tends to increase with the increase in methanol injection into the intake manifold. Under the present test conditions, with 10% (by volume) methanol injection, the increase in KLCR was 0.93 for spark advance of 30;The 10% methanol injection seems to be the optimal for best knock control because higher rates of methanol injection do not produce much more significant gains.