Quote:
Originally Posted by Wonderbar
No charger will, but forced air loses less % of power at altitude than an NA motor. Turbos and s/c were actually designed for use in piston powered aircraft motors to still have power at flying altitudes.
Example; when I was in Colorado Springs, an NA car would lose about 18% horsepower when compared to the same NA car at sea level. A turbo car would only lose about 5% and a supercharged car about 4-5%.
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Well, in theory here is how altitude effects N/A and FI (temp and dew point being constant) you have to use absolute station pressures, with SL (14.5 psi) & ~4000' (13 psi) and 5 psi gauge for FI as an example.
N/A: 14.5/13 = -11.5%
Turbo with gauge reference: 19.5/18 = -8.3%
Turbo with abs reference (BMW, Audi, others?): 19.5/~19.5 = ~ 0%
Mech super: 19.5/17.5 = -11.5% *fixed speed relation to engine so PR applies. so 5psi @ SL will be 4.5psi @ 4000'.
FTS 19.5/17.75 = -10% (compressor rpm increases slightly due to lower density @ altitude, so PR is up, ~ 1/2 way between a turbo an mech super)
SC piston aircraft (WW II) had 2 gear ratios (low alt and high alt) since it does not compensate for altitude. Modern turbo aircraft engines primarily 'turbo normalize' to maintain +SL performance regardless of elevation.
So..Fenton racing a BMW 135i which can maintain nearly zero loss @ altitude..nice!
Rob