Topic: What is detonation, pinging?

Here's what's going on in the cylinders inside the engine during pinging or knocking:

http://i280.photobucket.com/albums/kk184/RXi_20v/ping1.gif

Illustration #1 The piston begins to move upwards during what's called the, "compression stroke," compressing a mixture of fuel and air.

http://i280.photobucket.com/albums/kk184/RXi_20v/ping2.gif

Illustration #2 In a normally operating engine, the spark from the spark plug ignites the mixture of fuel and air, causing an extremely rapid burning of the fuel in the cylinder. That's good. It's what creates the pressure that makes the piston travel down very fast, causing the crankshaft, your transmission, and ultimately the wheels — to turn.

http://i280.photobucket.com/albums/kk184/RXi_20v/ping3a.gif

Illustration #3 However, it's possible for the mixture of gas and air to burn somewhere else in the cylinder, simply from the pressure (or compression) within the cylinder, and not from the spark. That's called "pre-ignition," and it's more likely in a high-compression engine. Illustration #3 However, it's possible for the mixture of gas and air to burn somewhere else in the cylinder, simply from the pressure (or compression) within the cylinder, and not from the spark. That's called "pre-ignition," and it's more likely in a high-compression engine.

http://i280.photobucket.com/albums/kk184/RXi_20v/ping4.gif

Illustration #4 When the fire you want (that's the one from the spark plug), collides with the fire you don't want (that's the one resulting from the pre-ignition), the result is a ping or, if the pre-ignition fire is big enough, a knock. The degree of severity, including the amount of noise generated, is determined by how big that unwanted flame is.


-- First posted by DonnieB

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Re: What is detonation, pinging?

nice post

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Re: What is detonation, pinging?

retard the timming

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Re: What is detonation, pinging?

one thing that bothers me with this is that by retarding the timing of the "wanted" flame front, makes the problem go away....  this in essence means that pre ignition takes place as the result of the sudden spike in combustion chamber pressure, as the main flame-front starts to move away from the plug tips(it being a bit early and all)....  we are  talking micro seconds after the spark...  so it's not exactly "pre-ignition" for if it was,  pulling back on timing would not have had any impact on it....  yes?

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Re: What is detonation, pinging?

interesting #Rotor- This is just a guess of logic from me-if the timing is not right the cyclinder pushing down will pull the spark away from the plug causing the point where the air, fuel and spark ignite to be lower in the cyclinder camber-thus causing preignition(think you said this). It is micor seconds(but micro seconds is a big deal if it off) so by sorting the timing of the inlet valves which allows the air and fuel in, the point of ignition(fire) will happen where it should.
Any gurus willing to help on this one??

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Re: What is detonation, pinging?

Very Nice article.Thanks

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