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Re: Turbos at Altitude

On Thu, 21 Mar 1996, Terry Donohue wrote:

> >Living in CA I regularly drive my car to 7-8K feet and have little
> >trouble finding the wastegate, even at altitude.

i have gone up to 3000 feet in my supercharged corrado and have
found that it feels every bit as powerful at that altitude as sea
level.  the v8 feels noticeably more sluggish but the thinner air
makes it easier to rev higher.

>  As far as I can tell, our cars control it relative to atmospheric
> pressure.  For instance, a stock '89-'90 200TQ allows 0.4 bar above
> atmospheric (or 0.8 in the case of mine with modified wastegate spring,
> etc.).  Thus at whether you're at sea level or 7,000 feet, when you first
> turn on the ignition, the boost gauge will read 1.0; at full boost it will
> read 1.4, but at 7,000 feet, atmospheric pressure is actually  0.77 bar, so
> you're really operating at 1.17 bar.

is this really the case?  i always thought that the wastegate would
simply open at a predetermined pressure regardless of what atmospheric
pressure was.  i always thought that it was the reason why turbos
are popular in places like denver.

and most aviation piston engines had superchargers and turbochargers too.