Altitude change

[C5 TT]

What can I expect when I have an altitude change of 7000 ft? I will be starting at sea level, which is where I live, and driving to Montana to an elevation of about 7000 ft. for the weekend with some autocrossing.
Should I plan on adjusting my tune to compensate for the altitude change while I am at that altitude for the weekend?

I am running a C5 Corvette with a TT setup. I am still running with the MAF.

What if I had an SD tune, would that make a difference?

[KAZ MotorSports]

As a high altitude tuner, I have done many experiments with SD and MAF controlled cars. MAF will compensate easily...SD will need a full retune depending on the measured air density where it was tuned and where it ultimately ends up to be run. I have seen air density levels in Texas on a hot, humid, low pressure system day that was 4000' above sea-level. In Colorado Springs on a perfect dry, cold, high pressure system day that was reading nearly 4500' above sea-level density.

Ultimately most of it depends on your setup to compensate for the less dense air. If your turbos and intercooler are efficient at sea-level it does not necessarily mean they will be at high altitude. Turbos that work at their peak efficiency at sea-level have to work harder and spin faster to compress the same amount of air at high altitude to get the same boost levels and flow of air. Working harder means hotter air out of the compressor housing which inturn means the intercooler has to wick out MORE hot air than if it was in more dense air. Charge temps rise and the end result is hotter less dense air entering the combustion chamber.

Be prepared for a couple of things. For sure your turbos will take longer to spool than at sea-level. Also your compression ratio in the motor drops. Thus you end up with a weaker torque curve to turn your wheels and accelerate the car until the turbos wake up. She will definitely feel lower on power than what you are used to at lower elevations.

Hope this helps,
-Kenny

ps...if your travels bring you through Colorado Springs you are more than welcome to swing by our shop for a quick baseline run to see your power loss. We may be able to dial in a few more ponies for you if you wanted. Are you running Methanol Injection? If you are used to seeing your numbers produced by a Dyno-Jet or other inertia style dyno be prepared for unruly low numbers. We use a Dyno Dynamics machine...aka The Ego Breaker.

[C5 TT]

Thanks for the information.

[KAZ MotorSports]

Anytime. Did you get a chance to run in the thin air?

-Kenny

[oztracktuning]

Tweaking B0304 will likely help at high altitude.
I have only tested to 4000 feet but 0.500000
0.570801
0.641357
0.712158
0.782959
0.853516
0.924316
0.995117
1.000000

Seemed to help.

[C5 TT]

Kenny, I have not had a chance to run at a higher altitude yet for any length of time.
Maybe this summer.

Thanks for the information oztracktuning I will give it try later.