if the IM has vac on decel: what relative psi in EM?... say you are decellerating from a wot pull at approximately 6000 rpm, throttle plate closes, bpv vents, im vac is present. How does the intake manifold vac effect exhaust manifold pressure ?

 

I doubt anyone other, than FP, has recorded pressure in the exhaust manifold. IIRC Robert @ FP did post a thread a long long time ago that contained EM pressure data.

I'm not sure what you are really trying to solve or address, but you could just give FP a call.

 

well, i dont need exact figures, but ive heard that there can be a good amount of BP in a turbo EM(~50iiiiiiiiish) I just wonder what kind of changes are gone through as soon as you lift . The intake tract closing off Im assuming puts this EM pressure very near atmo I would speculate...

Somone else mighjt have measured too..

 

No idea and not sure why it is even important....The big restriction is the turbo. The engine won't be pumping as much air in your scenario as when WOT at 6K rpm, so I would expect the back pressure in the exhaust manifold to be less than peak under WOT conditions. Again, not really sure why you care or what you are trying to solve for.

 

Im not trying to discover any thing tangable. ... however I would have to say there is some tuning knowledge for me to me gained. Like how an engine responds to timing changes as you lift, decel........ mash throttle lather rinse repeat