Re: 91 200'isms

[Robert Myers <rmyers@wvit.wvnet.edu>]

Imagine going toward the other extreme.  Imagine going up a "mountain" until
you reach a total vacuum.  There is no air present, therefore, no air to
compress with your turbo compressor.  The ambient pressure would be zero and
your manifold pressure would also be zero.  Granted, this extreme is not
attainable on the surface of Earth, but the trend should be obvious.

Maximum manifold pressure will decrease with decreasing ambient pressure.  
The effect of a wastegate is ignored here.  It will have an effect only at
higher pressures, not toward the low pressure end.

At 04:13 PM 3/15/96 -0800, you wrote:
>On Mar 15,  3:23pm, Eliot Lim wrote:
>> Subject: Re: 91 200'isms
>>
>> On 15 Mar 1996, Joe Yakubik wrote:
>>
>> > hits 1.7 bar on a daily basis @ 2000 ft altitude; 1.8 bar nearer to sea
>level
>>
>> perhaps this has been a long time misconception of mine, but i always
>> thought that turbos would produce the same manifold intake pressure
>				        ^^^^^^^^^^^^^^^^^^^^^^^^^^^
>> regardless of altitude..
>
>	This would be true (if *I* understand it correctly, of course!)
>	if your compressor had enough capacity.  I believe this is usually
>	*not* the case: manifold pressure may be wastegate limited at
>	sea-level, but get into the mountains, and the turbo running full-tilt
>	will still not trigger the wastegate.
>
>	Presumably (as mentioned in a previous thread), making a turbo
>	larger would give it enough excess capacity to maintain maximum
>	boost at any altitude, but that would result in ridiculous turbo lag
>	times.
>
>	-Arun
>
>
>
>Arun Rao
>Scientist
>Pixar
>1001 W. Cutting Blvd.
>Pt. Richmond, CA 94804
>(510)215-3526
>
>

___
	Bob 
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