I came across a question about wasted spark systems, and I was wondering whether there is a risk of prematurely igniting the incoming fresh mixture charge with that wasted spark.
At the top of the exhaust stroke, the inlet valve is opened already. An inlet valve timing of say, 20 degrees before TDC isn't uncommon, and ignition advance can be less than that. This means that these two overlap.
So with the right conditions concerning engine speed and engine load etc, I guess there's a chance that there's a bit of fresh mixture sucked into the cylinder already, when it isn't at it's TDC, nor at the time of ignition yet. Especially with forced induction engines. The wasted spark then could ignite that incoming charge. In the worst case, the flame could propagate throught the intake port.
These are all just guesses though, but i'm curious why it doesn't happen. Is it that the mixture isn't inflammable yet at this point? Or is it impossible for an intake charge to be forced into the cylinder so early, even when the inletvalve is already opening?
I'm curious about your theories!