Originally posted by SlprTeg
True, but to keep the manifold pressure the same, the turbo will have to spin faster. And when the turbo reaches its limits, then you will start losing power because the turbo cant make up for the lack of boost. And aince you are leaking boost, you are slowing down the turbo's cycle, causing boost lag. That air/fuel that got lost would have spooled the turbo alot better if it had combusted releasing its energy.
Last I checked, higher density fluids pushed out lower density fluids from the same occupied space. Again, overlap is between the exhaust and intake stroke, lasts very few
thousandths of a second, and if a bit of fresh a/f mix makes it into the turbo manifold unburned, who cares? It's still a higher density charge at a lower temperature, sure it won't expand as much as if it were burnt, but volume is relative to heat, so it will expand as it's passing through the turbine. You will not cause lag due to valve overlap, you will cause worse lag if you try to run with very small or zero overlap.
I know you are not so naive, that you think that the intake charge will push out 100% of the exhaust gases. They will intermingle, causing a vortex due to the extreme pressure differences. Which will amke it virtually impossilble not to leak boost and retain some exhaust gas in the chamber.
100% efficiency is the goal, not the result.
Explain to me how there's going to be an extreme pressure difference from a boosted intake charge entering the cylinder at the same time a boosted, burnt exhaust charge is exiting? Extreme temperature difference I'll give you, the pressure I won't, even in NA engines, gases attempt to disperse to gain an equilibrium pressure once released, the hotter exhaust gasses will always be at a higher pressure, until the exhaust valve opens. It really doesn't matter what the pressure of the incoming charge is, you are trying to deal more with port designs and vortices than merely the interaction of gases with heat and pressures.