jakedvmhi

Does anyone have any info on what normal power loss of turbo vs normal aspiration when gaining elevation (What is normal % loss)?

Pat-SoCal

I don't think there is a for sure way to calculate. Humidity is a big factor

Richard Solomon

Search the archives, I beat this to death all the time Short answer: modern turbocharged engines use an ABSOLUTE pressure sensor in the intake manifold to regulate the wastegate, thus they produce the SAME manifold pressure regardless of altitude.

Yes, you can't cheat physics, turbos spin faster, boost may take longer to achieve, etc, etc, etc but peak HP should be approximately the same until you get so high that the turbos spin out of their efficiency range.

It *IS* possible to calculate this, if one had the KKK K03 compressor map - which I have searched for in vain. (Not the generic K-class map on the web: that one doesn't seem to have numbers on it.)

M3EATR

Horsepower is dependent upon a number of air properties: humidity, density, temperature, viscosity. I was a mechanical engineer in my schools days and am trying to remember back to my fluids class. If we just look at altitude versus air density, here are some numbers:
Altitude(meters), density factor
0000, 1.000
1000, .9075
2000, .8217
4000, .6689
This won't be exact, but close enough for argument's sake. So, you can see that at 1000meters that the density is about 10% less(.9075). When I run around the mountains at about 10,000'(3,000m) I should see around a 30% loss in power(somewhere around .7). This sounds about right because I used to have a Jetta GLX and when I was going through the mountains I could swear that I lost close to 60Hp from the about 185 I was pumping out at sea level. Cars are just gasping for breath at those altitudes. That's why I bought the S4 -- forced induction. Now if someone can just help me out with my problem below under "S4 Failed Turbo @ 2K miles, Altitude Effect?"

jakedvmhi

Thanks, anybody know of any links that might have some numbers?

ÅllroÅd :DFW

I took a trip to Taos, NM and noticed that with 91 octane gas vs 93, there was a slight loss in power+turbo lag was very pronounced.

RocketJohn

5% UPTO 10,000' DUNNO ABOUT HIGHER ELEVATION...