Date: Sun, 22 Aug 2010 13:19:09 -0700
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: Garcia's Ghost doesn't like gettin' high.
Content-Type: text/plain; format=flowed; charset="utf-8"; reply-type=original
Hi Dave and all -
re
"make the stuff burn faster than it would at that altitude if it were 87
octane"
I suspect you just made that up. The reason lower octane is used at higher
altitude is there is no need for the higher octane level required at lower
altitude.
"Octane" is a measure of resistance to detonation in the combustion
chamber. At higher altitude, there is less pressure in the cylinders, thus a
lower octane fuel will suffice.
Scott
----- Original Message -----
From: "Dave Mcneely" <mcneely4@COX.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Sunday, August 22, 2010 7:05 AM
Subject: Re: Garcia's Ghost doesn't like gettin' high.
> 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
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