Altitude sickness or fact of life?

[Zaurusman]

I know my Protege's 2.0 isn't exactly a torque monster or anything, but I was really surprised by how much it slowed down through the San Juan Mountains in Colorado on vacation last week. At one point I was down in third gear with the car trying to return to the 45 mph speed limit. Is this the norm for the Protege and something I have to get used to with four cylinder engines (though I sure loved the whopping 41 mpg it returned for that leg!), or does it sound like maybe the MAP sensor (if Mazdas have 'em) is faulty? Is there anything that will specifically help altitude issues, or is it simply the math of air density and all that? It was also noticably less punchy in Santa Fe and Colorado Springs, which are both around 6,000 feet up, compared to Dallas which is pretty close to sea level. I expected less performance, but it was glaringly obvious to the butt dyno, and I had to re-learn how to start out in 1st with the stick after I bogged it a few times and nearly stalled it once. That's a big difference!

Air filter is almost new, throttle body was cleaned while in Colorado Springs.

TIA

[goldstar]

This has nothing to do with the fact that your car is a Protege or has a 4-cylinder engine. The phenomenon you noted is strictly a function of decreasing air density with increasing elevation.

For example, SAE net HP for the normally aspirated 2.0L engine is 130 at 77 deg F and sea level elevation. At 6000', the HP is reduced to 104 because of reduced air density. For more information, go to:
http://www.slowgt.com/Calc2.htm#BasAltCal

[justanotheradikt]

but i thought modern cars adjusted pretty good to the difference in air density? old carb cars sucked when you moved them around.

[keleko]

just use NAWWWWWWWWZZ at high altitude, bo-ii!

[pro00]

I have the same problem with my car going over some mountains in west VA.
I don't think it is anythng wrong with your car, just that less air density phenomenom.
But then, there were civics that were passing me up the hill with more ease. Now, i don't know if they were flooring it or not. I had the windows up.

[Zaurusman]

I've flown through west VA's mountains in my V6 Dakota at 75+ with the air and cruise on, and my Protege beats it 0-60 ... I guess that's why I'm so surprised the car's so much slower in the mountains. I wouldn't have thought the difference between 16.4 lbs/lb-ft torque and 20 lbs/lb-ft torque would be that massive to be the difference between 75+ and 40-45 mph at altitude, particularly when the Protege has it by 1.5 lbs horsepower-wise.

Thanks for the link, goldstar. Does torque follow the same general calculation as horsepower?

[Kooldino]

but i thought modern cars adjusted pretty good to the difference in air density? old carb cars sucked when you moved them around.

Yeah, they'll adjust to match the amount of fuel to the mass of air entering the motor, but the point is that a lower mass of air is entering the motor at high altitude.

[Zaurusman]

Here's a new question: Does a turbocharged engine suffer the same thing due to less intake thus less exhaust to run the turbo? Or does it consistently create the psi it's designed to regardless of altitude?

I suppose that if my MAP sensor were bad, I'd have run really rich in the mountains, huh?

[Jeph]

A Turbocharged engine suffers the same fate unfortunately. And to answer your other question, my car ran 2 more pounds of boost when it got back from Arizona which is about 4000 feet below Utah.

[Zaurusman]

This is all good to know as I consider possibly moving to Colorado. Thanks, guys!