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Effect of elevation on carb tuning

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Lin

Lin

Jedi Knight
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Sorry, I meant to ask in my post about Going Mobile:

What are the recommendations on adjustment to SUs for traveling at elevation. Mine are tuned for driving in Virginia at about 1000 ft. I am around 7,000 ft. now and anticipate that I may run into some problems tomorrow.

Lin
 
Hi,the air is "thinner"so mixture will tend to be richer,it depends how long you are going to be at that altitude,if the car has no noticeable running problems ,I would not bother to adjust anything,as to get optimum mixture you will be making adjustments every time you change altitude,it's better to be running a bit rich than too lean,better to have plugs a bit sooty than the possible engine damage and running hotter from being too lean.If really affecting running then lean the mixture out a bit on each carb
 
Hi Lin, if you run into running problems first lean the carbs as has been stated. Real sluggish performance may require a slight timing adjustment too. However, I have run at 9000 Ft elevations and just suffered with the power loss until back at lower elevations., of course this running was not for a prolonged time.Cheers-Keoke
 
Or we (Ric and I) could hook you up with EFI which will do the adjusting for you :smile:.....

Seriously, it was great to meet the Going Mobile team yesterday! A caravan of beautiful cars out for a amazing tour!!!..what could be better. If you were running okay going over Moument pass on the way to my place (over 7,000 ft. running 75 mph) you may well be okay until you get to a lower elevation. Sorry I didn't think to pull a plug to see what it looked like.

Cheers,
Steve
 
Well fellows, Thanks for the feedback and advice. I decided to not change anything this morning. We went over Monarch pass (11,300 feet) without much of a problem. The car clearly didn't like it. I lost power but no real problems and no hiccups. So I will plan to leave the carbs alone for now.

Lin
 
Hey Lin. Great to hear your trip is going well...

Several years ago I drove across country in a Mustang convertible (a modern one - 1986 - w/EFI) I owned at the time. I lost power at higher elevations as well, but also remember the fuel being different. I know it was lower octane. Maybe that's changed over the years, but just thought I'd mention it as a possibility...

I imagine you're over the mountains now. Best of luck. I have my car back now. I leave in a little less than two weeks for Georgia.

- Devin

Edited to remove route question... just saw your other post about the return route.
 
I seem to have heard that with sea level settings you lose approximately 5% power for each 1000 foot increase of elevation. I did not change mixture or timing when I ran out to Tahoe in 2002 and never noticed a real loss of power except when going up the very steep Pike's Peak road (14K+ elevation at the summit). I don't remember that overheating was an issue on that climb--we weren't going very fast--but the needle did almost peg on the long high-speed pull up Monarch pass
 
Thanks for the suggestions and comments. I decided to simply go a quarter turn leaner while in the mountains. It did help with running but particularly with idle in the small towns on route 50. I will just readjust when I drop out of the elevation.

Lin
 
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