joblo1978

iTrader: (14)

I just moved to Colorado from Virginia. I went from sea level to 6000+ feet. My mileage is horrible now, approx. 250 mi. to a tank and the power loss is very noticeable. I can no longer chirp 2nd gear. Is this normal or could there be something else wrong with the car? I understand that the oxygen levels are not as high here and some performance loss is to be expected...but this much?

Unaffliated Racing

iTrader: (15)

the air is just too thin up high..it has to take in a lot more air just to stay running.

Michael Ozorowsky

iTrader: (1)

I'm LUCKY to get 250 miles to a tank.

tomaSS

iTrader: (1)

Me too! More like 220 miles to a tank and I am at 2300 feet in Vegas.

P Mack

iTrader: (6)

You should expect a loss of about 20% at that altitude. I know my car feels like it pulls harder in 3rd in San Antonio than in 1st at 7000 ft. My mileage seems to be better at high altitude though, and it should be.

8-Pack

Its just the air, ever try running at high elevation, its the same principle. 250 to a tank isnt horrible, I can normally get 300 if I drive right.

ktmrider

20% loss is about right. We are the same elevation as Denver here in ABQ, so you must be in CS or so.
Not only is there less oxygen content at the higher elevations ( main reason for MPG loss ) but the atmospheric pressure is considerably lower too. Less volume of air overall being "pushed" into the cylinders. Basic internal combustion engine definition = air pump.
Either way, it sucks sometimes. Just think tho, when you go down to a lower elevation next time it will feel like you installed a supercharger! J/K, trying to put a positive spin on things for ya.

VaNDaL*SS*

iTrader: (1)

**** i get like 220 here, but im like only a 100ft over sea level if that!

f-bodman

Exactly, the same reason an engine performs worse when you remove a supercharger from it.... less pressure.

hugger1975

iTrader: (3)

get off the pedal.
i get 300miles per tank minimum in CO
Im from chicago, know what u mean about noticable power loss.


---thats why i am doin a 233/239 in feb!!!!!!!

P Mack

iTrader: (6)

At lower altitudes I don't think there is a gain from the pressure on the intake stroke because the piston also has to push against more pressure on the exhaust stroke, not to mention there is more pressure on the other side of the piston in the crankcase. I think it all evens out. The real gain is from higher cylinder pressure after combustion due to more oxygen being in the cylinder.

Joblo, where'd you move to?

J-Rod

I would disagree. Look at a DA calculation. Barometric pressure increase mean an increase in atmospheric pressure. Denser air means more air. More air=more hp. When air is cold and dry and dense (like in the dead of winter when a Northern cold front blows through) you'll see the DA drop into the negatives here. When that happens you can pick up to 9% gross HP.

Joker

Look at the vehicles that run the Pikes Peak hill climb; some of these cars/trucks actually have air being injected like gasoline into the combustion chambers from compressed air tanks to help with the thin air up there. Like everyone has stated here, the motor is a big air pump and the less air density, the harder it has to work with less so the output is less...

P Mack

iTrader: (6)

Yes, I know more pressure means denser air. I'm talking about pumping losses.

P Mack

iTrader: (6)

I reread my post and I guess it's not very clear. On a 4-stroke engine there is the intake, compression, power, and exhaust stroke. All the power comes from the power stroke, and it takes power on the intake, compression, and exhaust strokes. The power it takes to pull air into the cylinder and push the exhaust out is called pumping losses. No doubt you will make more power on the power stroke with a more dense intake charge. But some people have said that the power lost due to pumping losses is greater at higher altitude, and I don't think they are.

SScam68

iTrader: (20)

I am getting 30-31mpg doing 75mph with an M6 going from Albuquerque to Santa Fe (~55mi) on my commute to work. I actually tested it out for several weeks. At 85mph it drops to 26-27mpg.

Albuquerques elevation is 5000 ft and Santa Fe's elevation is 7000ft. I test engines for emissions purposes and depending on a given day we ususally correct our results to about 22%.

joblo1978

iTrader: (14)

Thanks for all the quick replies everyone. I moved to Colorado Springs.