Date:         Sun, 22 Aug 2010 09:05:35 -0500
Reply-To:     mcneely4@COX.NET
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Dave Mcneely <mcneely4@COX.NET>
Subject:      Re: Garcia's Ghost doesn't like gettin' high.
Comments: To: Greg Potts <greg@POTTSFAMILY.CA>
In-Reply-To:  <4C7083CB.80007@pottsfamily.ca>
Content-Type: text/plain; charset=utf-8

Robert, the high altitude mix should actually be lower octane than you get at lower altitude.  87 is usual below 3000 ft.  I have noticed on numerous trips out West that once I get above 3000 ft, the octane is usually either 85 or 86.  That is to compensate for the lower atmospheric pressure -- make the stuff burn faster than it would at that altitude if it were 87 octane.  But, if your van has any breathing problems at all, as you have noticed, 9000 ft doesn't provide much air, therefore drop in running efficiency.  I used to select higher octane fuel at altitude, but that was actually a mistake.

Don't know what one does with modern cars to offset the atmospheric pressure drop.  I used to, with an old Dodge Dart (with carburetor), take the cover off the air filter (reverse it).  The air still had to go through the filter, but there was a greater volume of air.  I don't know if that reduced the filtering efficiency, but at the time (I was a kid, 22-25 years old) I reasoned that the air was cleaner in Colorado mountains than in Texas.  Maybe.  But it did give me enough air to get over the passes.  David

---- Greg Potts <greg@POTTSFAMILY.CA> wrote:
> Hi Robert,
>
> Rule of thumb says you are losing 3% of HP for every 1000' altitude.
>
> The ECU can correct the mixture, but it can't increase the O2 content of
> the intake air.
>
> Happy Trails,
>
> Greg Potts
> Toronto, Ontario Canada
> 197x Westfakia "Bob the Tomato"
> 1987 Wolfsburg Weekender Hardtop
> www.pottsfamily.ca
>
> BUSES OF THE CORN - AUGUST 13-15th, 2010
> www.busesofthecorn.ca
>
>
> On 8/21/2010 4:31 PM, Robert Fisher wrote:
> > My van does not run well at high altitude. When we came here to Mammoth last
> > year the van lost a considerable amount of power after running normally the
> > whole way up here, and despite the fact that I filled up on local gas. I
> > don't remember the octane, but it was one of those pumps where you have
> > three choices for one hose and I think I'd remember picking something other
> > than the usual 87... on the other hand you'd think that "regular" here would
> > be a high-altitude formulation. I am going to try to remember to check it on
> > the way back through town.
> > This time I filled up on 87 in Bishop with the same results. Everywhere we
> > go here is between 8&  9 thousand feet; in addition to the low power it's
> > difficult to start when cold, to the point that I actually have to goose the
> > gas until it smooths out. Is there some point where the ECU can no longer
> > compensate well for the altitude, or does this point to another problem?
> >
> > On another distantly related note, I've noticed that the wood fires here
> > seem to smoke much more than at lower elevations... is there anything to
> > that?
> >
> > Cya,
> > Robert
> >
>
>
> --

--
David McNeely