Date:         Mon, 11 Mar 2002 16:52:49 -0500
Reply-To:     "G. Matthew Bulley" <gmbulley@BULLEY-HEWLETT.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         "G. Matthew Bulley" <gmbulley@BULLEY-HEWLETT.COM>
Organization: Bulley-Hewlett
Subject:      Re: Loss of power at altitude
In-Reply-To:  <50750ECDD09ED411AF9A00508B6A823B7C0775@harp.interval.com>
Content-Type: text/plain; charset="us-ascii"

Beyond the loss of O2 (which isn't the chief issue for loss of power
described), you also significantly loose the amount of atmosphere
stacked on top of you when you go up a mountain.

It is the weight of the atmosphere that pushes the air into the
cylinders on a non-super-charged engine, and the atmosphere at higher
altitudes has much less weight than sea-level. I know this can be
confusing, because we always think of the piston "sucking" air in... it
*really* isn't, though.

It is merely getting out of the way, and whatever weight of atmosphere
is available at that place will do its best to rush through the air
filter, past the throttle, and into the place where the piston was
moments prior. Again... it took me a little think time to digest this,
but it is the root.

Boosting fuel will only take you outside the stoichiometric ratio, since
there isn't enough air coming in to match it. The only (sorta) solution
is to supercharge, either with an exhaust-driven charger, or a
mechanical-driven charger...

Lurking, and popping up on the Vanagon list since 1997,

G. Matthew Bulley
Bulley-Hewlett
Corporate Communications
Business: www.bulley-hewlett.com
Alliance: www.ntara.com
Call tollfree: +1.877.658.1278


-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf
Of Aaron Reams
Sent: Monday, March 11, 2002 3:00 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Loss of power at altitude

Yeah, that makes sense... but the loss of power was very significant.
For
example, the loss of power in other vehicles like my jeep is negligible
if
even noticeable for the same drive.

Note: On a gradual incline at altitude I was in second gear and slowing
(<
23 mph).  At sea level on the same incline I could easily accelerate in
3rd
and probably maintain in 4th (> 40mph).

Thanks for the response!

Aaron



>Nope you got less oxygen and so less power at altitude.  I forget the
exact
>figures but you lose a bunch of HP at 8000 feet.