An Investigation on Low-Speed Pre-Ignition Mechanism in a Turbocharged Direct Injection Gasoline Engine

Abstract

Low-Speed Pre-Ignition (LSPI) has been regarded to be caused by auto-ignition of lubricant which is diluted by fuel impinged on liner wall. This paper shows the results of numerical simulation and experiment for analyzing the LSPI mechanism. Simulation results indicated that flame propagation can be started by auto-ignition of lubricant before spark ignition timing, and then unburned mixture (end gas) cause knock due to compression by flame propagation. Experimental results showed that auto-ignition occurs even if quite small amount of lubricant is included in fuel droplets splashing from piston crevice into cylinder.