How does altitude effect horsepower? Are there any sites that can explain it?

 

probly because the pressure or something

 

the air density changes the amount of air compressed into the engine to make the same amount of horsepower. tc applications have a larger effect due to the amount of air being compressed.

 

The higher you go, generally the more power you lose. This is even more pronounced with naturally-aspirated diesels, as the atmospheric pressure is less (The air is thinner.). Forced induction is the way to go at high-altitude. It is MORE than a replacement for displacement. Injection seems to self-compensate much better than a carb (MPI moreso than TBI), but carbs can be adjusted specifically for an altitude range using different jets and needles. Both will lose powerif theydon't have forced induction though. Even my buddy's 5.7LHemiGrand Cherokee, while still quite powerful,loses noticeable pep above 8K ft. His brother's stock 4.0L I6 Rubicon couldn't even hold the speed limit with it's life-sucking autountil we swapped in a CAI.Free-flowing intakes and exhausts can help a lot. My 2.5L I4/5spd YJ pulls grades ok, if I downshift,with stock gears and 31" tires, but I run a K&N in a de-restricted airbox with a free-flowing exhaust. I've even towed from CO with my 4-banger Heep.

Surprisingly, my stock '00 VP sedan w/autopulled the grades just fine too. I even had to be extremely careful driving I-70 out of Denver in the snow because the car would break traction every time it downshifted just maintaining speed. When the snow cleared, the 1.6L Civic zipped around without a problem. The Rubicon didn'thave enough ***** to evenmake it's tranny downshift, with the accelerator floored on the highway. We putted along, losing speed (down to like 30MPH), until Isuggested to just downshift it manually. We had to make that engine scream to maintain the speed limit (ridiculous for a 4.0L).I think it's got a service bulletin or something for that tranny's computernow. (IMO, the only thing that tranny's good for is heating the underside of the Jeep to clear it of snow buildup.) To be fair, most naturally-aspriated cars I've driven through the mountains have seemed kind of gutless. After hot-roddingmy 2.5L up and down passesthough (with a similar MPI setup), the 4.0L Rubicon was a shocking disappointment. Cars with forced induction absolutely FLY though. Even a Dodge Sprinter at max gross weight can handle mountain passes with it's tiny turbo-diesel I5.

If you google the effects of altitude on engines, you should easily be able to find how to calculate power loss at different elevations. Sometimes naturally-aspirated engines won't even run, if you go high enough. (Try pull-starting a snowmobile at 12K ft.)

 

Well I havea Civic, and live at 5,280 feet (Denver). I was just wondering what the difference would be if i went down to sea level.

 

Once your computer adjusted (someadjust faster than others), you'd likely have a bit more pep if you're naturally-aspirated. You'd especially notice it starting off and on steeper highway grades. Your car will feel a lot more "torquey". You may also have to run a slightly higher octane and/or alter your timing to avoid pinging/knock. I haven't had to though.