I just moved from a city at 5,000 feet above sea level to one that is 3,000 feet above. How much horsepower do I gain for the 2,000 foot decrease? Is there a formula to calculate the loss or gain for an increase or decrease in altitude? Someone posted a formula, but it has been so long ago that I can't remember it.

After guessing low on my off nitrous hp (haven't dyno'd with mods), I'm losing 6.92868hp just for being in Oklahoma. (while we're doing math, anyone care to figure out what I put in as my hp?) I will paypal you $1. Edit: @1276ft.

OUCH! Using your formula my equation would be: 2950 x .03 x 160 / 1000 = 14.16 hp loss. Meaning 160 drops to 145.84. 160 to 146. Guess I'll have to go turbo! Thanks for the info. Floyd P.S. Guess this explains why my 95 Ranger V6 seems like it's become a 4 cylinder.

Algebra isn't my strong suit but I believe you used 181 as your hp figure...keep the buck, you can buy me a beer if we ever meet up for a ride.

You did the math right, but made the wrong conclusion. Your horsepower is greatest at sea level and decreases as you go up in altitude. Say at sea level, your HP is 160. At 3000 ft, your power loss is 3000 x .03 x 160 = 14.2 resulting in 160 - 14.2 = 145.8 hp At 5000 ft, your power loss is 5000 x .03 x 160 = 24.0 resulting in 160 - 14.2 = 136.0 hp So, by moving from 5000 ft down to 3000 ft, you picked up about 10 hp.

I think I did 182 but it comes out almost the same at 181. people just don't ever get rewarded for using math anymore!

3% is a rough rule of thumb. The higher the RMP which hp is developed at, the more the altitude penalty will be. For expample it means a Duc 1198 will lose less hp than a GSX-R 1000 when going up in altitude.

about 3% per 1,000'. I am at 2,800' elevation in Boise, ID. I love going to sea level tracks or riding at sea level. Turbo is not really effected by elevation as long as the turbo is big enough to build the same amount of boost at elevation. I ride snowmobiles any where from 5,000'-9,500' elevation. Their is no comparing a turbo sled hp at elevation to a NA snowmobile no matter what engine mods and pipe they have.

Some aircraft use what is known as a "turbonormalizer." This is a system that increases boost to keep the effective intake pressure the same as sea level. Thus an engine at high altitude produces the same horsepower as it does at sea level. Before the advent of jet engines, high-performance piston engined aircraft like WWII fighters used two stage compressors (turbo or supercharged, and combinations thereof) so that they could operate with decent power above 20,000 feet MSL. While a Busa just loses power as it is operated at higher altitudes, airplanes have competing factors. My plane loses significant power as it is operated at higher altitudes, and less power means lower speed. At the same time, the lower air density also allows the airplane to move faster relative to the ground, so losing power but also losing drag. A magic combination happens about 7000 to 8000 feet MSL, where the reduced drag more than makes up for the loss of horsepower, resulting in the fastest speed. (which is, sadly, just a tad lower than a Busa at sea level . But then I can go 175 all day without fear of a speeding ticket or wiping out in the turns! )