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Something else to think about in the scenario that the waste spark is igniting anything at the top of the exhaust stroke. Let's say the a/f mixture went through the ignition cycle without lighting off. Now the piston drops and uncompresses the mixture.
When this occurs, isn't some of the heat from the previous compression now drawn out from the decompression?
When an a/f mixture is decompressed, does some of the mixture condense into larger droplets from the previous vaporized state, due to the drop in pressure and temperature?
Isn't most of the charge expelled from the cylinder way before the 24 or so degrees before TDC of the exhaust stroke? In fact, most likely past the turbo by this point with a short runner exhaust system?
The piston speed is very slow by 24 degrees BTDC exhaust stroke. In tuned exhaust systems, the charge would have exited the primary tube and a low pressure pulse would have traveled back up the primary and would be pulling residual and the next intake charge into the chamber by this time. Assuming a large overlap camshaft and the unburned charge would be traveling at the same speed through the primary tube as a higher volume and pressure burned charge, which I realize it wouldn't.
I would think that if the charge that was expelled from the cylinder did light off, it lit off way before 24 degrees before TDC ex somewhere in the exhaust system from exhaust system heat.
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