Date:         Sun, 22 Aug 2010 09:03:25 -0700
Reply-To:     Don Hanson <dhanson928@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Don Hanson <dhanson928@GMAIL.COM>
Subject:      Re: Garcia's Ghost doesn't like gettin' high.
In-Reply-To:  <01c401cb41ab$1bd75120$6801a8c0@PROSPERITY>
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On Sat, Aug 21, 2010 at 8:35 PM, Scott Daniel - Turbovans <
scottdaniel@turbovans.com> wrote:

> power loss due to altitude is gradual.
> like if your engine has 100 hp at sea level..
> 90 hp at say 7,000 feet.
> one poster said 3 hp per 1,000 feet gain I think...sounds about right.
>

  Power loss due to elevation is not linear.  There are layers in our
atmosphere, it is stratified.  The HP loss due to elevation is not a smooth
curve.  Up to >5000' of elevation the 02 content doesn't change very quickly
or with much effect on 02-sensitive systems....systems like internal
combustion engines or human athletes.  At around 5000' above sea level there
is a distinct and relatively sharp decrease in the O2 content.  At 5000'
elevation and up, your power loss 'comes on' quickly and noticeably .  From
my experience, you can consider <5000' as one "zone", normal elevation,  and
above 5000' your can think 'high elevation'.  There is another 'sharp'
decrease in O2 somewhere around 13,000' but of course, no roads that high so
N/A as far as engines are concerned.
  I would guess the 3% of hp per 1000' goes something like...a few % power
loss only,  until around 5000' elevation and then about 15% between 5000'
and 7000'.   I found some graphs online showing this curve, but don't have
those handy.


>
>
> for a 'cant' get out of it's own way' ..
>

  I drive through that area around Mammoth Lakes in California (Hwy 395,
etc)  often and I've done a bicycle race out of the Owens Valley (Bishop,
Ca., elevation around 4500') .  At Bishop's elevation, everything is
relatively normal but once up the Sherman Grade (tops out around
8000'?)...power loss really happens.  I often  find myself checking to see
if my parking brake is on by mistake as I near the summit of that Sherman
Grade.  When racing my bicycle there in what is a brutal, mainly climbing,
race,  after descending back to the Owens Valley floor between the
consecutive  mountain climbs,  it feels like you almost get 'super-charged'
by all that "extra oxygen"...(yeah, right...)  Check out the elevation
profile of the bike race below. Other info on that area in the EC race
website too... an austere but spectacular part of California.

http://www.everestchallenge.com/page1.ihtml?id=10




> So without resorting to a spreadsheet- I've lost a third of my horsepower?
>> Good grief.
>> I guess my main question is: Is there a point (that can be expressed in
>> altitude) at which the ECU can no longer adjust the mixture? Any of you
>> Boulderites want to weigh in?
>> Btw, the cold start problem seems to be related to flooding.
>>
>> Cya,
>> Robert
>>
>
   "A third of my horsepower"?  Close to that, I guess.  Significant,
anyhow.  Your van is probably not 'acting up', it just 'sucks' at high
elevation and doesn't get any air...
  There is a Vanagon-centric shop in Bishop, said to be good.  I bet he has
first-hand experience with Vanagon behavior at those elevations and could
give you some specific information..
  Elevations like that is where forced induction engines come into their
element.  You can program the boost to give your motor adequate oxygen for
optimum combustion, where a Normally aspirated motor, the ECU has to reduce
the amount of fuel to match the reduced available 02 in order to keep the
optimum combustion (stoichmetric) mix.  It is amazing the advantage a
supercharged or turbocharged has at elevation...
  Don Hanson

  Don Hanson