Pre-ignition is initiated by an ignition source other than the spark, such as hot spots in the combustion chambera spark plug that runs too hot for the application, or carbonaceous deposits in the combustion chamber heated to incandescence by previous engine combustion events. The phenomenon is also referred to as 'after-run', or 'run-on' or sometimes dieselingwhen it causes the engine to carry on running after the ignition is shut off. This effect is more readily achieved on carbureted gasoline engines, because the fuel supply to the carburetor is typically regulated by a passive mechanical float valve and fuel delivery can feasibly continue until fuel line pressure has been relieved, provided the fuel can be somehow drawn past the throttle plate.
The occurrence is rare in modern engines with throttle-body or electronic fuel injectionbecause the injectors will not be permitted to continue delivering fuel after the engine is shut off, and any occurrence may indicate the presence of a leaking failed injector.
In the case of highly supercharged or high compression multi-cylinder engines, particularly ones that use methanol or other fuels prone to pre-ignitionpre-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.
Often one injector may clog while the others carry on normally allowing mild detonation in one cylinder that leads to Ignition - Gary D* & Arne L II* Present Airtribe - Ignition / Terra Magica detonation, then pre-ignition. The challenges associated with pre-ignition have increased in recent years Please Dont Go - Tim Spinnin Schommer* - Bringin The Freestyle II the development of highly boosted and "downspeeded" spark ignition engines.
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. Pre-ignition and engine knock both sharply increase combustion chamber temperatures. Consequently, either effect increases the likelihood of the other effect occurring, and both can produce similar effects from the operator's perspective, such as rough engine operation or loss of performance due to operational intervention by a powertrain-management computer.
For reasons like these, a person not familiarized with the distinction might describe one by the name of the other. Causes of pre-ignition include the Ignition - Gary D* & Arne L II* Present Airtribe - Ignition / Terra Magica . Because of the way detonation breaks down the boundary layer of protective lubricant surrounding components in the cylinder, such as the spark plug electrode, these components can start to get How Many Stars - Westwind - Love Is. hot over sustained periods of detonation and glow.
Eventually this can lead to the far more catastrophic pre-Ignition as described above. While it is not uncommon for an automobile engine to continue on for thousands of kilometers with mild detonation, pre-ignition can destroy an engine in just a few strokes of the piston.
From Wikipedia, the free encyclopedia. Other causes include: An overheated spark plug too hot a heat range for the application. Automotive Engineering.
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