If you are passing through the higher elevations with a turbo then the
computer will compensate for it and you won't notice a lot of difference.

Ok, it's knock sensor will start retarding if the boost pressure mapping
doesn't understand whats going on, and it probably will
And my aviation point was also wrong, as the aircraft have to take-off at
sea level!

However, surely all of these high States are not at that altitude and surely
one has to take the worst case, which is running around at more like Sea
Level than right high-up. Taking an average case, you could get damage, it
only takes a few seconds or less of detonation to do serious harm at high
throttle openings. I also can't see that having differing fuel specs all
over the place is in any way a good thing, or easy to administer, or even
cheaper having non-standard mixes. Octane ratings higher than the minimum
required don't actually do damage to an engine, like  a brief spell of
detonation, just your wallet

The DJ needs 93 minimum at Sea level. It runs a 10.5:1 CR as standard from
the factory. It goes better with 98, Super Unleaded and does another mpg
maybe.

Clive Smith

----- Original Message -----
From: "John Brush" <jbrush@AROS.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Thursday, July 11, 2002 4:19 PM
Subject: Re: 85 octane in Colorado

> >business, indeed -
> >read anything Ricardo related - a giant among motor engineers.
>
> Interesting. I guess the whole country, and the oil companies, have got it
> wrong......
>
> >And what if you drive into Colorado in  a turbo or supercharged car? If a
> >manufacturer states 95, 93, 91 minimum octane rating, that's generally
> >what they mean.
>
> The moment you cross the border into Colorado with a turbo or a
> supercharger, you car will cease to function..................
>
> The manufacturer will state an octane rating for the elevation that the
> car is to be operated at. There will be a footnote about changes to be
> made if the elevation is increased.
>
> >My DJ would have a problem on Super Colorado!
>
> Since there are plenty of turbos and superchargers on the highway in
> Colorado, I would say the prevailing thought process of less octane at
> higher elevations is pretty much correct.
>
> If you are passing through the higher elevations with a turbo then the
> computer will compensate for it and you won't notice a lot of difference.
> If you live there, your computer/engine combo will probably be different
> than that of a person living at sea level.
>
> John