cummins cowboy

so lets say you have a custom tune, be it a dyno tune or a tune that comes with your hand held tuner, lets also say this tune set a specific AF ratio at or near sea level, does the AF automatically adjust for higher alititude?? so if I have my car tuned at 700 ft, will the AF ratio remain the same at 7000 ft elevation??

loudnlow

I wouldn't think so. I noticed last year on my road trip from Utah to California my car ran totally different. I would think it would have to be adjusted somewhat but maybe the ratio difference would be minimal.

SirKnightTG

It's going to run different in higher altitudes due to it not being able to pull in as much air, because it can't burn as much gas. The PCM will adjust to maintain stoich (14.7).

So if you're pulling in less air in the high altitudes, it will pull fuel to maintain that 14.7 ratio. Less fuel = less power.

So yes, you should still get the same ratios.