Research of Knocking Deterioration due to Accumulated Carbon Deposits on Piston Surfaces

The quantity of heavy components in fuel is increasing as automotive fuels diversify, and engine oil formulations are becoming more complex. These trends result in the formation of larger amounts of carbon deposits as reaction byproducts during combustion, potentially worsening the susceptibility of the engine to knock [1]. The research described in this paper aimed to identify the mechanism that causes knocking to deteriorate due to carbon deposits in low to medium engine load ranges, which are mainly used when the vehicle drives off and accelerates. With this objective, the cylinder temperature and pressure with and without deposits were measured, and it was found that knocking deteriorates in a certain range of ignition timing. Additionally, this paper reports the results of an investigation into the relationship between the rate at which the ignition is retarded by the knocking control system (KCS) and the time required to eliminate knocking; this was carried out to help formulate a control plan to resolve the effects of knocking deterioration.