Re: Turbos at Altitude

["Richard Klein" <rklein@cris.com>]

On 21 Mar 96 at 21:24, Terry Donohue wrote:

> you're really operating at 1.17 bar.  I know Porsche controls their turbos
> in an absolute sense, so they can get full boost even at higher altitudes.
> Is there any way to do this on Audis?  I'm particularly interested in this
> since I'm about to move from Chicago (700 ft.) to Tucson (2400 ft on up to
> 9,000 ft).  Getting turbos to run at full boost absolute at higher
> altitudes is one real advantage we have over aspros (look at results from
> Pike's Peak for confirmation).

Tuscon's higher above sea level than Chicago, but the air is dryer.  
Am I correct in thinking that water vapor isn't useful for 
combustion?  If so, you'll have less useless mass in the combustion 
chamber and more room for oxygen, which would offset the 
disadvantages of altitude to some extent.

On another hand (I think I need 3 at this point), water injection is 
sometimes used to reduce a tendency for detonation, so more water 
vapor in the air (and combustion chamber) might allow higher 
compression ratios, more advanced timing, more boost, or lower octane 
fuel.

I'm sorry I'm not answering your question (absolute boost v. 
relative boost)...

   -Rich

   '85 Audi 5000s   '72 Suzuki GT380
   '85 El Camino SS '73 Suzuki GT550 in pieces

    in beautiful Bay City, Michigan "Unity in adversity"