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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.
When the flame moves backward it may also be called a "pop-back". A backfire can be caused either by ignition that happens with an exhaust valve open or unburnt fuel making its way into the hot exhaust system. A visible flame may momentarily shoot out of the exhaust pipe. A backfire is often a sign that the engine is improperly tuned.
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The reduced engine speeds allow more time for autoignition chemistry to complete thus promoting the possibility of pre-ignition and so called "mega-knock". Under these circumstances, there is still significant debate as to the sources of the pre-ignition event. [3] Pre-ignition and engine knock both sharply increase combustion chamber temperatures.
It's commonly known as "Detonation or Knock". Engine management systems can overcome pre ignition by the means of a knock or detonation sensor. The sensor will detect pre ignition and retard the engines timing to protect the engine from damage. Undesired engine behavior will occur such as loss of performance or power.
Crankcase dilution occurs when the fuel oil from the engine gets into the lube oil of the engine. This can be caused by the walls being wetted due to the fuel condensing in the cylinder. If the engine is cold, or there is an excess amount of cooling around the cylinder, [ 1 ] the fuel oil will condense and have a higher chance to end up in the ...
Dieseling (in the sense of engine run-on, and disregarding combustible gaseous mixtures via the air intake) can also occur in diesel engines, when the piston or seals fail due to overheating, admitting engine oil into the cylinder. A structurally failing diesel engine will often accelerate when the throttle is released, even after fuel ...