Originally Posted by
CaudleDynamicsLLC
I had to sit down and study that a bit more, the axis/scale for the green line isn't showing, but with it peaking at TDC compression and staying steady while either valve is open it seems to me to correlate more to cylinder pressure as opposed to intake port pressure? I think all the information in that one picture is extremely valuable. If that is indeed cylinder pressure, it would be awesome to also overlay pressure in the intake port, maybe between the valve and injector. I'd tend to agree that the differential between the two pressure sensors (cylinder and port), especially when also compared to overall intake manifold pressure, should give you a pretty reasonable idea when and if there really is significant reversion into the intake, when air actually starts flowing back the correct direction past the injector, and possibly, how much delay between SOIT and fuel actually getting past the valve. That level of detail seems like it would still probably be very combination dependent though and would have to be tested a stock or negative overlap cam, and also on an aggressive positive overlap cam. With air having inertia and a "springiness" to it, there may be interesting pressure waves and reversions even on small cams that this whole EOIT study would benefit.
On further thought, it would probably have to be tested on a running engine with combustion and thermal effects though, since hundreds/thousands degree F air surely behaves differently than air pumped through by motoring the engine, and if we are looking at pressure differentials, we'd certainly want cylinder pressures to be relevant.