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The expansion of the gases still pushes the piston in only one direction, no matter where the crankshaft is.

CompUser wrote: ...

A most interesting and informative article. Thank you!

It seems that what I learned many years ago about engine knock (and overconfidently echoed in this topic) is quite wrong, and I stand corrected. Read it for yourself to understand.

Of course, but before TDC it is the wrong way, and after TDC it is the right way. You don't want any expansion of gases to occur before TDC.

I'm withdrawing from this silly discussion because CompUser in a post above referred us to an article that brings me up to date on the problem of knocking. He was right.

Uncle Ben

Well, yeah, the TDC thing is correct, but that is a matter of timing: "WHEN the piston gets pushed", not what DIRECTION the piston gets pushed. I was confused when you said the piston gets pushed the wrong direction by the expanding gasses-- and the expanding gasses can only push the piston in one direction!