NEW TECHNOLOGIES, NEW ISSUES
The move to smaller engines with more torque and better fuel economy might seem like all up-side for drivers, but today’s smaller, hotter-running engines pose significant challenges to lubricants. The latest is a phenomenon called low-speed pre-ignition (LSPI), also known as "super knock," which can destroy pistons and connecting rods.
WHAT IS LSPI?
LSPI is another version of engine knock, which has been around since engines were invented. In this case, it occurs under low-speed, high-torque conditions in turbocharged gasoline direct-injected engines and is more destructive than typical engine knock.
Under normal operation, spark-triggered ignition is timed to work in tandem with downward piston momentum. LSPI occurs when an oil/fuel droplet hiding in the piston crevice launches into the combustion chamber and ignites the fuel/air mixture too early. The resulting force clashes with the upward moving piston and can cause damage like that on the piston shown.