Quote:
Originally Posted by mechman600
I'm not sure if a bit more backpressure really matters. I used to think it does, but not anymore.
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depends on what you call a bit, dont know what engine you are thinking of either, but if it is a 7 litre job, running @ 4000 rpm, putting out 50 PSI, with a bore/stroke of say 4 inches (keep me honest here):
it has to push 50 sq inches of piston area, at 50 psi for 4 inches every revolution
so thats about 2500 pounds of force, for 1/3 a foot or 840 foot pounds per rev
or about 3350000 foot pounds per minute @ 4000rpm, or over 100hp!!
Of course the intake is presumably pressurized too, so that would offset the losses by the ratio of intake PSI to exhaust PSI. i.e. if the intake is at 25psi, you would be spending a total of 50hp just on backpressure. If I figure this right.