Abstract:

Boost and direct injection are effective measurements for energy saving in gasoline engines, while
super-knock has become the main obstacle for further improving power density. Pre-ignition and superknock
are two different combustion phenomena. Super-knock is a kind of severe engine knock in high power
density internal combustion engine, which generally occurs at low-speed, high-load operating conditions
with stochastic, sporadic and destructive. Pre-ignition is a abnormal combustion phenomenon in spark
ignition engine that ignition occurs before the spark timing. Pre-ignition itself does not always lead to superknock,
however, pre-ignition accures before super-knock. To eliminate pre-ignition is an effective approach
to suppress super-knock. The origins of pre-ignition include oil droplet and particle. The composition and
physicochemical properties of fuel and oil affect seriously the frequency of super-knock.

Key words: boost gasoline engine, super-knock, pre-ignition, oil droplet, deposit