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      06-14-2013, 12:01 PM   #59
Malek@MRF
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Drives: E92 M3, E46 M3, G82 M4
Join Date: Jan 2008
Location: Irvine, California

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Quote:
Originally Posted by M&M View Post
Ok I see I emphasize the word QUANTITY and everyone keeps harping on about the ratio. Of course the ratio is the same. There is still 80/20 Nitrogen vs oxygen. But there's less O2 and less Nitrogen. You may end up climbing up to the top of Everest and you may end up getting 2 02 molecules and 8 Nitrogen molecules in each gasp of air (not actual numbers, I'm just trying to illustrate that the ratio stays the same).
The ratio will always remain the same, unless you are using this M3 somewhere other than planet Earth.

This "quantity" you are referring to is known as D.A. (Density at Altitude).

Bob MG is correct, all he will have to do to compensate for his altitude is very basic, and he is already on track to doing it. Superchargers and turbocharger systems do not respond the same way in regards to D.A. The turbo will continue to compress air without the wastegate opening until the target pressure is acheived, it does not care what altitude it is at. The CF supercharged car will generate boost as a function of crank speed and SC pulley speed. Alter the ratio between these two, and you effectively alter the boost pressure (given that D.A. does not change along with ambient temperature). The SC car will be affected by D.A. because it does not have a wastegate boost control system, it is predefined in pulley size and RPM. The higher up you go, the less boost the SC car will generate. Much like in NA form, the SC car will suffer power at higher altitude.
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