Ok we made it back from a trip into the mountains - Breckenridge, CO. The truck ran strong for about 500 miles to Denver, then we hit altitude and the power was left in Denver. Low end was fine but high end was not there, which was fine I guess because all I needed was low end to climb all the other snow covered stuff for three days. I really didnt think that the altitude would dampen the power that much, but when we came back down to Denver, the power rejoined us. I was more curious about if I could have changed the settings on the Evo to correct for the air/gas mixture in high altitudes and since I will be traveling that way again soon, I thought I would throw the question out. Thanks!

 

There is something about high altitudes in the Edge manual. I don't remember exactly but I think retarding the timing is what you would have needed to do.

 

Actually, no. You COULD advance the timing a bit for the higher altitude. Because the air density is so low, gas has a lower tendency to pre-iginte. Also, the colder temperatures cause the same effect. I can't remember off the top of my head the exact amount. I seem to remember something like 0.5 degrees of advance for each 2,000 feet? However, the gas they sell is about 2 octane points lower than what it would be at sea level too, so I wouldn't be in a hurry to advance the spark.

But really, the reason you lost power is because the air is MUCH less dense. At 18,000 feet, the atmospheric pressure is about half what it is at sea level. Breck is what, about 10,000 feet? The atmospheric pressure is probably somewhere between 3/4 to 2/3 of what it was at sea level there. In the military, you MUST be breathing supplemental oxygen when flying above 10,000 feet (cabin altitude). Less oxygen means less fuel can be burned, and, less power results.

When I drive over the high passes in Colorado, I just "live with it".

- Jack