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In spark-ignition internal combustion engines, knocking (also knock, detonation, spark knock, pinging or pinking) occurs when combustion of some of the air/fuel mixture in the cylinder does not result from propagation of the flame front ignited by the spark plug, but when one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front.
Pressure in cylinder pattern in dependence on ignition timing: (a) - misfire, (b) too soon, (c) optimal, (d) too late. In a spark ignition internal combustion engine, ignition timing is the timing, relative to the current piston position and crankshaft angle, of the release of a spark in the combustion chamber near the end of the compression stroke.
Common causes of backfire are running rich (too much fuel going into cylinders) or faulty ignition, possibly a fouled (dirty) spark plug, coil, or plug wire. Pop-backs are usually caused by problems with timing. If the timing is too early, the spark plug fires before the intake valves close, causing the combustion to propagate into the intake ...
The high compression ratio in the auxiliary combustion chamber causes the auto-ignition of the homogeneous lean air-fuel mixture therein (no spark plug required); the burnt gas bursts - through some "transfer ports", just before the TDC - into the main combustion chamber triggering its auto-ignition. The engine needs not be structurally stronger.
In the case of highly supercharged or high compression multi-cylinder engines, pre-ignition can quickly melt or burn pistons since the power generated by other still functioning pistons will force the overheated ones along no matter how early the mix pre-ignites. Many engines have suffered such failure where improper fuel delivery is present.
The double exhaust pulse would cause part of the next exhaust pulse in that bank to not exit that cylinder completely and cause either a detonation (because of a lean air-fuel ratio (AFR)), or a misfire due to a rich AFR, depending on how much of the double pulse was left and what the mixture of that pulse was. [5]
To explain these phenomena, consider a flame that is stabilized with swirl, as in a gas-turbine combustor, or with a bluff body. Moreover, say that the chemical composition and flow conditions are such that the flame is burning vigorously, and that the former is set by the fuel-oxidizer ratio (see air-fuel ratio ) and the latter by the oncoming ...
Crankcase dilution is a phenomenon of internal combustion engines in which unburned diesel or gasoline accumulates in the crankcase.Excessively rich fuel mixture or incomplete combustion allows a certain amount of fuel to pass down between the pistons and cylinder walls and dilute the engine oil.