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Altitude effect on 135i turbos
I was considering an 07 EVO before I decided to wait for the 1er and discovered that in that car the turbo makes up about 1/2 the difference in altitude (i.e. cylinder air pressure difference at 5000 feet is halved compared to a naturally aspirated car).
Does anyone know how the 1er computer handles altitude difference? I've heard people guess that it makes up the complete difference, but this would increase lag quite a bit. The turbos would have to spool up quite a bit faster to make up the pressure difference, and this seems counter to BMW's intention for the engine.
I have an '02 A4 1.8T auto and it is a dog when I go up into the mountains (8,000+). The shift points go way up, and even after the turbo spins up the car is generating way less power than it does even in Denver at 5200 feet.
This question is also important in determining whether it makes sense to mix 100 octane in with the 91 I get at the pump - if there isn't enough air in the cylinder at altitude it wouldn't matter.
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