Originally Posted By TRENDZ
This from your last post GTX MATT...

"I'm looking at it from the standpoint of the valve is closed, there's some # of boost in the intake manifold behind the valve, now the valve opens and its going to fill the cylinder in less time that at 0 PSI."

Hard to argue if that's where it ends. But that's not where it ends. What is the pressure on the other side of the intake valve when under boost?
The cylinder has only two points of reference, the intake charge, and the exhaust. As boost increases, so does exhaust pressure. It doesn't matter if it's supercharged or turbocharged... exhaust pressure gets very high under boost. So at best, cylinder fill starts to happen (loosely)at around a 1:1 pressure ratio.


Correct, I would say it absolutely doesn't end at the intake valve, once the intake valve starts to open the pressure wave is now going through the cylinder and into the exhaust path (assuming overlap) until the exhaust valve closes, then its ending at wherever the top of the piston is. Pressure on the other side of the valve changes depending on where the piston is of course, cam specs, etc. But it should be less than the pressure on the intake side of the valve under boost.

Last edited by GTX MATT; 11/10/17 02:52 PM.

Now I need to pin those needles, got to feel that heat
Hear my motor screamin while I'm tearin up the street