Re: Turbos at Altitude

[ptimmerm@mashtun.JPL.NASA.GOV]

>  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 itwill
> read 1.4, but at 7,000 feet, atmospheric pressureisactually0.77 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.

	The above paragraph uses some flawed math.  There may be some
	effect, but there are two sources of pressure on the WG.  First
	and formost is the spring, secondly is air pressure.  First is
	not effected.  The second may be.  Probably not with a car that
	uses a frquencey vavle on the WG.  Definetly not with the
	schrappnel knobben, maybe a little with an open atmosperic port.
	Certainly less than cited above, although he was right is will
	be linear, the magnitude of the change will be lower than 
	calculated.  In some cases approaching 0.0.

	paul timmerman