Re: 91 200'isms

[Albert Ng <ang@copper.ucs.indiana.edu>]

Yeah, you are right. In low ambient pressure the wastegate should keep 
close longer to maintain the manifold pressure. But for what I mean is,  
at a certain altitude(maybe more higher) the situation won't happen the 
same as you menthioned. The wastegate will fully open (by altitude sensor) 
to perevent the turbo overrevving since the turbo restriction is reduce 
by the thin air density. 

I really can't recall where I read this piece of info, but I think 
some member on the list can probably tell us more about this. :-)


Albert  Ng
'87 5kcst

On Sat, 16 Mar 1996, Robert Myers wrote:

> Albert,
> 
> It would make sense for there to be some sort of ambient air pressure
> measurement to allow better boost control.  But at lower ambient pressures
> you'd want the wastegate to stay closed longer, not open sooner.  Part of
> the "spring" holding the wastegate closed is atmospheric back pressure.  At
> lower ambient pressures (higher altitude) you need a stiffer spring to
> maintain the same absolute manifold pressure.
> 
> Is this 18 cents short of a paradigm?  :-)
> 
> At 12:41 PM 3/16/96 -0500, you wrote:
> >
> >Just my little something about this topic. I heard from somewhere a while 
> >ago that all the Audi 5kt car has a altitude sensor. If the car is operating 
> >at a certain altitude, the sensor will kick on and send signal to somewhere 
> >to fully open the wastegate. I don't know why they doing this, but, by my
>           ^^^^^^^^^^^^^^^^^^
> 
>                  ???
> 
> >guess, is that they want to keep the turbo spin slower since on a higher 
> >altitude the air density is lessen and the turbo will spin fast.  
> >
> >
> >Albert Ng
> >'87 5kcst
> 
> ---snip---
> 
> ___
> 	Bob 
> ********************************************************************
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>