Questions for you Rocky Mtn riders

[Mile Hi]

I have always heard that power loss is approximately 4.5% per 1000 feet. Anyone have different numbers? After the 95" build the dyno showed 95 hp, 99 tq which are basically sea level numbers I presume. So at 6000 feet, with a 4.5% loss per, all that expense for the 95" build gets me back to stock sea level. Bummer. Our thin air also brings up the question of heads/cfm flow, and how that will affect proper matching of parts. Seems to me that with all the considerations in a build, some things would need to be done differently at high altitude. Anyone have sound knowledge on this? When I moved to the Denver area in 1980 it sure seemed like at least a 25% loss on the Sporty, and my lungs as well. Would appreciate any info.

[disco]

Most natural aspirated engines are derated 3% per 1000 ft. elevation above 1500 ft. Only modification required is leaning out your fuel mixture. Where I live I can go from 3000 ft. to 7000 ft. and down to sea level in an 8 hour ride. God bless fuel injection!!!

Disco

[Warhawk]

Don't worry about it. I lived near Salt Lake for a couple of years and could be at 10,000 feet less than 40 miles from the house. There is a slight loss of power, but it's really not too noticeable until you go above 10K.

[Road Bag]

Originally Posted by Mile Hi

I have always heard that power loss is approximately 4.5% per 1000 feet. Anyone have different numbers? After the 95" build the dyno showed 95 hp, 99 tq which are basically sea level numbers I presume. So at 6000 feet, with a 4.5% loss per, all that expense for the 95" build gets me back to stock sea level. Bummer. Our thin air also brings up the question of heads/cfm flow, and how that will affect proper matching of parts. Seems to me that with all the considerations in a build, some things would need to be done differently at high altitude. Anyone have sound knowledge on this? When I moved to the Denver area in 1980 it sure seemed like at least a 25% loss on the Sporty, and my lungs as well. Would appreciate any info.

As you go up in elevation, your cranking pressure (static) and cylinder pressure (running) go down. If you were to never to ride down the mountain, you could certainly go up in compresion and advance the timing as well to regain cylinder presure and a little power with a more aggresive tune up. Your still going to be down on power overall. I think the only logical thing to do is step up and buy a Turbo. Thats right! Just pull out your CC and do it! Don't ask the wife, you already know what the answer would be. Just think, you'll have your own little air factory right on the side of your bike. 6000' my ass! Just reach down and give the wastegate a couple more turns and watch the elevation drop! Let us know how it works for ya.
RB