Anyone know what the effect of altitude is on the 2.0T and 3.2 engines in the 2007/2008 A4s? I'm at 5500ft. How much power and/or torque is lost? Does altitude affect just horsepower or torque as well?

 

I think it will effect both HP and torque. I heard somewhere that you loose like 5% of your HP for every 1000ft above sea level you are but don't quote me on that.

Josh

 

Since I posted the question I spent a while googling and found out the following so I'll answer my own question and hope it is helpful to others.
A normally aspirated engine will lose a little over 3% power per 1000ft of altitude. That is about 16% at 5000ft.So, the 3.2 engine power drops from 255hp to about 214hp.
A turbocharged engine will lose about 1.8-2% power per 1000ft of altitude. That is about 9-10% at 5000ft. So, the 2.0T engine power drops from 200hp to about 180hp.
So at 5000ft the 3.2 engine is still ahead of the 2.0T by about 34hp.
Some dealers in the Denver area will claim that the 2.0T and the 3.2 generate about the same horsepower when they tell you a normally aspirated engine loses power at altitude but what they forget (or don't know) is that the turbo enginealso loses power at altitude, though not quite as much. On the plains at 5000ft the 3.2 is ahead of the 2.0T by 34hp but at altitudes over 10,000ft such as for Vail and Aspen the 2.0T is about the same asthe 3.2.

 

Well I was some what close. LOL

Josh

 

mrvuml is right about the 3% per 1000 ft. A diverter valve that
holds more pressure might help at high altitude. Check this site:

http://www.grc.nasa.gov/WWW/K-12/airplane/atmosold.html

 

Affect