Quote:
Originally Posted by JohnAh
Cubic/square, that sounds clear, thanks!
I'm familiar with both "Pinging" and "detonation" as names for the condition when fuel ignites by preassure/temperature from another location than the spark plug. If I have understood right, the noise comes from two wavefronts/pressure waves meeting with a sharp mechanical chock as a result.
What I tried to describe is a phenomenon that keeps the engine running for some second or even more the moment after the ignition have been switched off. -Same words in english?
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You're welcome.
Generally, yes -- it's two wave fronts hitting each other. It can melt pistons, break ring lands, and damage bearings.
Running after shut off is called "dieseling," as the engine is running like a diesel with no ignition from a plug. It smells horrible and stings your eyes! This doesn't happen with electronic fuel injection, as the fuel is cut off, but can continue with mechanical injection or a carburetor. This is why some carburetors have a solenoid that the idle stop screw rests on while the ignition is on; it retracts when the ignition is shut off and shuts the throttle blade(s) completely (or nearly so) to shut off the air flow.