Date: Sun, 8 Jun 2003 21:50:45 -0500
Reply-To: John Rodgers <j_rodgers@CHARTER.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: John Rodgers <j_rodgers@CHARTER.NET>
Subject: Re: Degrading Comments
Content-Type: text/plain; charset=us-ascii; format=flowed
I can't speak to cazrs, but airplanes have a coulple of kinds of
superchargers.
One type is an internal supercharger and is inside the engine case. It
typically boosts pressure way above sealevel pressure and thereby
produces considderably more horepower.
Then there is the turbo-charger. This is typically driven by being
mounted in the exhaust system. Some have automatic wastegates that
maintain preset pressures. Some are designed to maintain sealevel
manifold pressure up to certain altitudes.
I would think that with a turbo on a car or van the ideal would be to
maintain sea level pressure even at altitude. On a normally aspirated
engine the maximum horsepower will be generated at a certain rpm, at
standard sea level pressure, compensated for temperature. I think
standard pressure is defined at 72 degrees F, at 29.92 inches of
mercury. (1050 millibars??) As you drive to altitudes you lose pressure,
as pressure is lost so is horsepower lost. If the pressure were
maintained as sea level pressure, ie, 29.92 inches, all the way up to
any altitude, then you would be able to maintain sea level horsepower.
The advantage to an airplane maintaining sea level horsepower up to
altitude is that the higher you go the less the drag on the airframe.
Thus if you can maintain sealevel horsepower while up to very thin air
with little air resistance, one could go like the proverbial "Bat out
of hell".
Regards,
John Rodgers
88 Gl Driver
David Marshall wrote:
>How does a turbo work then? I assume that 10 PSI boost means that the
>manifold pressure is 10 PSI greater than the atmosphere pressure. So
>wouldn't that mean that you are still making less power at altitude than at
>sea level? Perhaps I am totally wrong here - heck this is why I am asking
>the question! :-)
>
>David Marshall
>
>Fast Forward Automotive Inc.
>4356 Quesnel-Hixon Road
>Quesnel BC Canada V2J 6Z3
>
>http://www.fastforward.ca mailto:sales@fastforward.ca
>Phone: (250) 992 7775 FAX: (250) 992 1160
>
>- Vanagon Accessories and Engine Conversions
>- Vanagon, Transporter and Iltis Sales and Importation
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>
>
>Due to the large volume of email we receive, PLEASE include previous
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>
>-----Original Message-----
>From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com]On Behalf
>Of Dennis Haynes
>Sent: June 6, 2003 6:18 PM
>To: vanagon@GERRY.VANAGON.COM
>Subject: Re: Degrading Comments
>
>
>A naturally aspirated engine will lose 3% for 1,000 feet of altitude.
>This goes for gasoline or Diesel. The major factor is decrease
>atmospheric pressure which will result in decreased cylinder charge.
>This why lower octane fuels such as 83 or 85 are used in high altitude
>areas.
>
>Dennis
>
>
>
>-----Original Message-----
>From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf
>Of Pensioner
>Sent: Friday, June 06, 2003 8:13 PM
>To: vanagon@GERRY.VANAGON.COM
>Subject: Degrading Comments
>
>Engine performance degradation as function of altitude? Data, numbers,
>curves, experiences? NB it has been pointed out that the air resistance
>actually decreases at altitude. I'm looking for engine performance
>numbers
>independent of van configuration.
>
>p
>
>
>
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