Concerns such as depletion of petroleum fuels and global warming
are placing more severe demands on internal combustion engines each
year for reduced fuel consumption and CO₂ emissions. Countries
around the world have set regulations that drastically reduce CO₂
emissions from vehicle exhaust. In order to meet these
requirements, various new engine technologies are being developed.
One of the technologies to cut CO₂ emissions of the SI engine is
the combination of reduced displacement, high compression ratio,
forced induction, and direct fuel injection. But in this downsized
engine, abnormal combustion, which occurs under the condition of
low speed and high intake pressure, is a serious problem. It has
been referred to as Super Knock, Mega Knock or Low Speed
Pre-Ignition (LSPI). In this paper, we use the term Super
Knock.
Many research institutions and car manufactures have been
investigating this abnormal combustion, but the exact cause is
still unknown.
The goal of this study is to investigate the cause of Super
Knock using a 1.6L in-line four-cylinder SI engine with direct
injection and turbocharging. By recreating Super Knock we
investigated its sensitivity in terms of both engine parameters and
spark plug characteristics. The results of these investigations are
reported in this paper.