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I just got back from a trip to Colorado and have a question. While driving west of Colorado Springs my car started losing power. I was going 55 to 60 and ended up barely going 40 to 45. I was at 7000 to 8000 elevation. I turned off the AC thinking that was the problem but no improvement. Had the car checked before and after the trip and the mechanic couldn't find anything wrong with the car.
It was a narrow two lane highway and I was backing up traffic. There were only a few places where I could pull over and let people pass. It was embarassing to say the least. The car is a 4cylinder Chevy Prizm. Usually
I've driven a 8 cylinder in the mountains and never had this problem.
A friend told me I should have downshifted from drive into 2nd but wouldn't that make the car go even slower?
Is there something I could have done differently?
Perhaps you had less atmospheric pressure on the engine in the higher elevations causing a loss of power?
No perhaps to it. A Prizm needs every bit of engine it comes with just to maintain highway speed. Thinner air at higher elevations will rob any engine of power, and that anemic 4 banger has none to spare.
At 8000 ft, your engine has about 2/3 of the power it did at closer to sea level due to the reduced oxygen in the air.
Your car engine is basically a pump that is powered by fuel and air being ignited. With less air/oxygen available at altitude to ignite, your horsepower suffers.
Depending on your gear ratios and speed, you could have manually shifted down to another gear.
I just got back from a trip to Colorado and have a question. While driving west of Colorado Springs my car started losing power. I was going 55 to 60 and ended up barely going 40 to 45. I was at 7000 to 8000 elevation. I turned off the AC thinking that was the problem but no improvement. Had the car checked before and after the trip and the mechanic couldn't find anything wrong with the car.
It was a narrow two lane highway and I was backing up traffic. There were only a few places where I could pull over and let people pass. It was embarassing to say the least. The car is a 4cylinder Chevy Prizm. Usually
I've driven a 8 cylinder in the mountains and never had this problem.
A friend told me I should have downshifted from drive into 2nd but wouldn't that make the car go even slower?
Is there something I could have done differently?
Combustion engines lose power at higher altitudes. This is especially true if the engine has no forced induction -- in other words, if it is not turbocharged or supercharged. As an aside, this is how semi tractors came to be turbocharged. Diesels require a lot of air as it is, and long-distance haulers could barely get over high-altitude mountain passes out west. Consolidated Freightways decided to build their own tractors, and Freightliner was born. Nowadays nearly all diesel engines are turbocharged.
Anyway, back to the subject at hand. At 8,000 feet, a car engine is making roughly 70% of the power it would be making at sea level. The small engine in your Prizm simply couldn't get enough air at high altitude to meet that power demands you were asking of it. The V8 you drove in a similar situation was experiencing the same rate of power loss; it just happened to have enough power in reserve to keep you moving.
All of the 'above', no pun intended...
Even our '02 Vette, which runs with almost anything on the road, was down a bit on power on many high passes and 10,000+ ft roads during our 13,000 mile Road Trip, this past summer. Normal...
GL, mD
"Top of the World" Bear Tooth Pass Highway, ~11,000 ft Wyoming
Icefield Parkway, Banff National Park Alberta, CDA
Last edited by motordavid; 09-12-2011 at 08:35 AM..
Location: We_tside PNW (Columbia Gorge) / CO / SA TX / Thailand
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Yes, Mtns + elevation can kill naturally aspirated 4 cyl engines. (Non-turbo). Your particular engine performs best at higher RPMs, thus a lower gear is essential when climbing. Autos with V8's typically have enough 'spare' power that loss at altitude is not noticeable to a 'recreational' driver.
Quote:
"Top of the World" Bear Tooth Pass, ~11,000 ft Wyoming
Years ago I had a 1966 4 cyl International Scout. Had a 2 jet carburetor. You reached in and slid a valve to swap over the smaller jet for high altitude.
People who live in high altitudes have their autos tuned for high altitude.
as the others have said, an engine loses power at higher altitudes, and the less power reserve you have, the worse things seem to be. downshifting does help as it turns the rpms up and let the engine make more power. but even that is limited as well.
as for forced induction, that really does help as it normalizes the engine power output to more like what it does at sea level. in fact turbos were put on some light aircraft for that reason. it was called turbo-normalizing.
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