Low Elevation to High Elevation

[oakley6575]

Hey guys, I'm from Las Vegas and I'm going to school in Southern Utah. The elevation change is from about 2,000ft to 6,000ft. When I'm in the lower elevation, my truck runs 200% better. It will spin the tires for as long as I want. But up at school, If I hammer the throttle at low mph, or even sometimes at a standstill, it has a very hard time breaking the tires loose. Why would it have such an effect on performance?

408 Iron Block
LS3 Top End
231/239 114
4L80E 3.42 gears

I can post the tune later today. Thanks for your help

[mecanicman]

Air pressure and density change with altitude. All the weight of the air above squishes the air below. So, the lower you are more air is present. When air is more dense there is more oxygen present. Also with more pressure it is easiar to force more air into a void(vacume) such as an engine. Lower altitude means more power. Whole reason for having a baro sensor and hp correction factors on dynos.

[Rinkrat456]

You effectively lost 15% of the oxygen molecules available for engine consumption. Have two tunes, one for school and another for home.

Then get 4.10's.

[04SilveradoMykk]

Essentially what your feeling is as if you reduced static compression of your engine. While in higher elevation you can run more ignition timing without knock, but it may not compensate for how much power was lost.

I started tuning at an elevation of 5400-6000ft (Prescott Az) and I've recently moved to Hollywood Ca.... still getting used to the differences of elevation

[oakley6575]

You effectively lost 15% of the oxygen molecules available for engine consumption. Have two tunes, one for school and another for home.

Then get 4.10's.

Yea I just took 410's out of my truck after I built the 408. Couldn't get traction through the first two gears. I put 3.42s to help that a little bit and make it a good highway cruiser for school. I'm getting 22.5mpg with this motor in a truck on the highway. Can't ask for much more than that. But I wish I could have 410s up in the elevation.

[oakley6575]

Essentially what your feeling is as if you reduced static compression of your engine. While in higher elevation you can run more ignition timing without knock, but it may not compensate for how much power was lost.

I started tuning at an elevation of 5400-6000ft (Prescott Az) and I've recently moved to Hollywood Ca.... still getting used to the differences of elevation

So what should I change besides adding some spark. Would you add some to the whole table?

[smithers]

Look at your MAP values, you probably go from 88kpa up to 101 which is in essence, adding ~1.8 psi of virtual boost.
More oxygen per volume of air = more fuel = more power.