Ok so i have read and heard people talk about driving there cars in high altitude.

high altitude = thinner air less oxygen.

So it makes sense that cars will lose alot of power in high altitude as the engine isnt getting as much air as sea level.

Thing i dont get is when some people talk about how driving your car in high altitude is dangerous or bad for it. this makes no sense.

running rich = safe but not as powerful
running lean = bad

Well higher the altitude the less oxygen molecules are in the air. so this means the car is getting the same amount of gas but less oxygen causing the car to run richer.

Make sense or am i missing something?

 

Yes, you are missing the fact that your ECU compensates for barometric pressure..... aka altitude so you still have the same A/F ratio's... less 02, less fuel.
This is also similar how your ECU compensates for air temp as well

 

i have to tell you that i lived at 8000 ft of elevation , and also we have a crappy gas , so the cars lost alot of hp .
i do not have reference on a evo on the dyno because we do not have aroun a 4 wheel drive dyno , but if some can get son dynosheet of a mustang gt 500 i have one here totally stock on dynojet without any cf , the at the wheels was 347 hp

 

What is "cf" referring to in this paragraph?

 

correction factor , at this altitud was 1.38 more o less dependes on the climate conditions

 

Correct me if I'm wrong but wouldn't a turbo couteract most of the power loss? i know turbocharged small aircraft can fly much higher since the engines won't lose power. But i am also not a mechanic.

 

A turbo brings you xx PSI above the pressure of the environment. If the pressure of the environment is lower to start with, the absolute pressure after the turbo will be too.

 

No.... a turbo certainly helps... the reason why aircraft have FI is to make more power than they could NA (w/o larger engines because that means weight)... the more power allows them to fly at higher altitudes, because at higher altitudes we all understand there is less air, which means less lift, so they have to fly faster.... and in this reference is why the speed of aircraft are referenced as MACH, because it is the relative speed compared to the speed of sound which changes by static temperature (which changes w/ altitude)

 

the more dense the air is, the better.

Also when it is colder out, the air is more dense..

 

However the wastegate spring is constant no matter what the barometric pressure. If its set to open at 15psi at sea level it's going to open at that same pressure regardless of altitude. The turbo will have work harder to open the wastegate and will be less efficient. This is why turbocharged engines do so well at altitude although they don't make as much power as sea level.

 

^^^^x2

 

bumping up this old thread, i live in a high altitude place, roughly around 5500ft above sea level, my car was tuned at sea level and when i took my car home ive noticed the idle dipping especially at stop lights to around 500 rpms, car shakes but never stalls, i recently brought the car down on an out of town trip and noticed the idle was more consistent at sea level, however the next day car was idling around 1100-1400 and wouldnt seem to go any lower till i got back home. im planning to bring the car back to the tuner soon cause i have informed him of the idle dipping. the idle drop is pretty annoying, does the altitude of where i live in have a direct effect on the idling? what adjustments should the tuner do to improve my idling at high altitude? maf and injector scaling? advance timing? any input would be very much appreciated. thanks.

 

I think the best thing would probably be to adjust the biss screw at altitude. There is a procedure for doing this, you will have to search.

On a side note, to clear up some miss information in this thread. The way your turbo will react to altitude depends greatly on how you are controlling boost. If you are using a manual boost controller then it uses current atmospheric pressure as a base line. So at sea level it would be 14.7 psi + 20 psi. if you are at 2000ft your base is 13.4 + 20psi. So effectively you have lost 1 psi of pressure. If you are using an Electronic Boost Controller (3-port etc) and a map sensor then your baseline is absolute 0 (bar/kPa) regardless of your altitude. So when you change altitude the ECU is targeting an absolute number. This means the Turbo may have to spin faster at higher altitude, but it will try and achieve the same bar/kPa at any altitude. Here is a neat chart if found http://www.sablesys.com/baro-altitude.html