Re: A4 2.8 vs 1.8T - altitude effects

[marriott@Summa4.COM]

Howdy,

A frequently-used approximation for NA engines is 1% horsepower lost per 
1000 feet elevation. This means the 2.8 and 1.8T are equal at 14600 feet.

> > Does a turbo make up for the loss of external air pressure - ie
> > charge 
> > pressurization is the same regardless of altitude? Would the knock 
> 
> Depends on how they program the wastegate in the computer.  Most likely
>  they
> allow a maximum Absolute pressure which would mean that there would be
> no loss in power.

Correct, as long as the ambient pressure/temperature isn't so low the turbo 
overspeeds trying to reach that level of boost. Most controllers know 
better than this, and it's mostly a problem with small turbos which are 
running close to their max. to begin with. If only I had to worry about 
this with my car :-(

cu
James



James Marriott, BSME
work:  Manchester, NH, USA  marriott@Summa4.COM (603)625-4050 x 2539
home:  Auburn, NH, USA      marriott@grolen.com (603)483-8587

'64 Falcon Sprint Convertible--balanced & blueprinted 260 V-8
    GOES great. Stopping? 217k
'86 4000S        the better half's commuter (heated seats), 100k+
'87 4000CSQ      H-stock auto-x und daily driver, Kanc-1 veteran, 137k

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