I live in New Mexico at 5,000 feet altitude. I heard that normally asperated engines loose around 4% of their horsepower for each 1,000 feet of elevation gain. My question is will I see a equal drop in the output of the Supercharged S, or will it be able to keep up? I test drove the vehicle in Phoenix and it will be shipped up here this week and I'm just wondering.
Thanks,
Fatbob

 

Hey Bob, the idea with superchargers and turbochargers is to keep the presure constant inside the engine, when you gain altitude the barometric presure or bar's is lower too, that means less air(OXIGEN, with all it cmponents)is contain in a molecule, but with a controlledatmotfere inside the enguinethis problem will be less.
So basically you will not have probles of HP decrease up there, I hope you enjoyed as much as I am.

 

I agree with you up to a point, supercharged and turbocharged engines lose less power at high altitudes compared to standard engines, however they do lose some power. As you pointed out, there is less oxygen available, therefore the computer has to dial back the fuel to keep the mixture within limits: less oxygen and less fuel= lower power.

 

I agree with everybody else. Another way to look at it is the way that I do when flying an airplane with a turbocharger. There is an altitude where the aircraft can no longer maintain seal level pressure with a turbo (usually somewhere above 7,000 feet). Once you reach that altitude, you will get less power.

My guess is that for a car, it is similar. You will no longer be able to generate full power in a MCS once you reach a certain altitude, but the real question would be what that altitude is. I would expect that at 4 - 5,000 feet, you wouldn't notice a difference.

 

in this context, the power limiting factor is the oxygen content in the cylinder during combustion; the fuel injection will mix gas in accordingly to get the correct mixture, based on how it measures oxygen content. at a higher altitude, a given volume of air contains less oxygen, so with the same boost as at sea level, you would be putting less oxygen in the cylinder at altitude and less air as well, since the boost pressure is a fixed ratio (at a given rpm) of in to out pressure.

with a carburetted engine, you would have to re-jet, booster or not, to compensate for the altitude, other things being equal. the fuel injection is cabable of making the same adjustment as re-jetting, but it is still limited to it's fuel map which may not be optimized for altitude.

 

4-5000 feet is nothing really to worry about in terms of power loss.

i have had my MCS over 12,000 feet on 5 seperate occasions now. Even at that elevation, the supercharger worked like a champ. The power loss is slight. The only thing I noticed was that when the car is pushed hard at 10,000+ ft that if you stop the fan will run for a while (4-5 minutes).

Hope that helps.

 

>>I agree with everybody else. Another way to look at it is the way that I do when flying an airplane with a turbocharger. There is an altitude where the aircraft can no longer maintain seal level pressure with a turbo (usually somewhere above 7,000 feet). Once you reach that altitude, you will get less power.
>>
>>My guess is that for a car, it is similar. You will no longer be able to generate full power in a MCS once you reach a certain altitude, but the real question would be what that altitude is. I would expect that at 4 - 5,000 feet, you wouldn't notice a difference.
Kdog...the a/c actually has a 'turbonormalizing' system which uses either an automatic or manual wastegate to control the boost. This system's purpose is not to increase h.p. but rather to enable the engine to develop it's maximum horsepower at a much higer altitude.
Automotive systems are designed to increase the horsepower of the engine under normal (i.e. sea level) conditions for performance. Since these systems do not general have adjustable wastegates, the boost is constant and does decrease with an increase in altitude. In the aircraft we adjust fuel flow and manifold pressures to compensate for changes in density altitude, but no so in our autos. ....Keep the dirty side down! c ya around the tarmac