lucas had asked "So the fuel is being burned after the piston is at the top or before or right at the top? "
The answer is all the above.
On a old car at idle, you set the ignition to 10 degrees BTC. Ignition thus starts and finishes at its own pace, regardless of engine speed. Combustion would finish after TC. Peak cylinder pressure occuring soon after TC.
The faster the engine is running, the farther the advance has to be, on the old car, thats what the distributor did.
Get things to far advanced and knock occures. Modren cars and computers test this, using an accelerometer to look for knock, then lessining the advance as needed.
Had an 1988 Thunderbird turbo, fun to run at the track, just unplug the knock sensor, advance the timming a bit, supprise the 5.0 mustang types.