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Re: Diesel knock sensors ever posible? ALL

"Pinging"/"knocking" in a spark ignited engine occurs when the heat and pressure of the fuel mixture that was lit by the spark plug rises to a point which exceeds the flash point of the remaining fuel mixture, causing it to ignite in a secondary location, often at the far end where the accumulated pressure is "trapped", instead of a smooth burn across the cylinder. These two separate areas of combustion (they're not explosions) collide and make one helluva noise. It's the shock wave that you hear. The measure of octane is a fuel's resistance to doing EXACTLY this detonation under pressure...the more it can stand without lighting itself off, the higher the octane number. All the cylinder conditions at the instant of combustion have their effect, and changing ignition timing is one of the most effective ways to reduce it, so there's an easy remedy.

A Diesel engine works by creating so much heat between the molecules of air by compressing it 2-3 times smaller than in a gasoline engine that combustion can occur, and then spraying a fine mist of fuel into the cylinder. The fuel is always being consumed (oxidized) at the injector as it is being metered. Unlike a gasoline engine, the fuel is not already in the cylinder when combustion starts so you CANNOT have "pinging" in a Diesel for the reasons you get it in a spark motor. That's not to say that Diesels don't make lotsa noise, we all know they do, but it's because the pressure rise is much higher and at a different rate.

I know that was a long way around the block to simply say "no" to your question.






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New Diesel knock sensors ever posible? [ALL]
posted by  someone claiming to be Bill D.  on Thu Dec 7 14:04 CST 2000 >


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