Correction factor different for turbo?
Correction factor different for turbo? How do correction factors (for altitude) work for turbocharged engines? The engine in question is a small aircraft engine, and the wastegate will keep the manifold pressure constant up to a certain altitude until it is all the way closed. It seems like the wastegate should keep the power about the same, but something tells me it's more complicated than that. We will be dynoing this engine at 7000ft, but the numbers need to be corrected for sea level.
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Joined: Nov 2001
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From: Las Cruces, NM
Originally Posted by P Mack
How do correction factors (for altitude) work for turbocharged engines? The engine in question is a small aircraft engine, and the wastegate will keep the manifold pressure constant up to a certain altitude until it is all the way closed. It seems like the wastegate should keep the power about the same, but something tells me it's more complicated than that. We will be dynoing this engine at 7000ft, but the numbers need to be corrected for sea level.
The wastegate will keep a constant pressure differential relative to the outside (barometric pressure)
So sealevel is 14.7 psia, 4200 feet is ~12.3 if you are running 5 psi of boost then at sea level you will get 19.7 psia and at 4200 feet you 17.3 psia. So your pressure ratio is the same. However, density/temperature ratio is not the same. Temperature produced by the turbo at higher altitudes will be higher than at sea level because the turbo is spinning much faster to produce the same boost. So now power will not be the same only boost levels.
This link along with associated pages should help http://wahiduddin.net/calc/calc_cf.htm
Gary
