SUV's at high altitude (octane, mileage, gas, head)

[Vision67]

I have a 2014 Ford Escape turbo 2.0 in Colorado. I love it.

It will maintain 75 mph in cruise up I-70 to the Eisenhower Tunnel at 11K feet.

So I punched it at that elevation. It accelerates like a scalded cat.

Fun car!

[Old Gringo]

My wife's 2009 Subaru Forester non-turbo regularly sees duty in the mountains of NM at 7000 - 9000 ft elevation and never misses a beat. If there's a difference in performance due to the elevation, it's slight.

[Colorado^]

Originally Posted by Old Gringo

My wife's 2009 Subaru Forester non-turbo regularly sees duty in the mountains of NM at 7000 - 9000 ft elevation and never misses a beat. If there's a difference in performance due to the elevation, it's slight.

It's ~3% loss in HP per 1,000ft.

[Old Gringo]

Originally Posted by Colorado^

It's ~3% loss in HP per 1,000ft.

I doubt it.

That would mean 21% to 27% which would be very evident.

It isn't at all evident.

[f5fstop]

Originally Posted by Colorado^

Now there's something we agree on. There should be a law against towing a travel trailer in Colorado with a gas engine. We'd all get to our destinations a lot sooner.

I tow quite well in CO with a gas engine and a trailer behind my rear bumper. I can do the speed limit up and over the passes I have traveled with no problem. Yea, I might use more fuel, yea it will downshift but you know, that's why they made auto transmissions that downshift. You just have to make sure you have enough truck engine for the load and know how to drive it.

So if you want a law for only diesels in the mountains, let's make them illegal where you don't need them? Sounds fair to a ludicrous statement!

[Colorado^]

Originally Posted by Old Gringo

I doubt it.

That would mean 21% to 27% which would be very evident.

It isn't at all evident.

It's a scientific fact.

HP Loss = (elevation x 0.03 x horsepower @ sea level)/1000 (google it).

However at altitude we usually have colder, drier air which is more dense. This help increase hp a little.. that's why we say ~3%.

But given identical humidity and temps, you lose 30% of your HP at 10Kft vs sea level.

[oberon_1]

Originally Posted by Old Gringo

My wife's 2009 Subaru Forester non-turbo regularly sees duty in the mountains of NM at 7000 - 9000 ft elevation and never misses a beat. If there's a difference in performance due to the elevation, it's slight.

Never misses a beat? How many HP is that?


Toi the OP: Yes, you suffer from significant power loss at such altitude. Maybe I missed it, but what's wrong with super charged or turbocharged engines?

[Old Gringo]

Originally Posted by oberon_1

Never misses a beat? How many HP is that?

Not enough to notice. It's a 2.5L four banger, so it doesn't have all that much go power to begin with. If it lost ~ 25% it should be very noticeable.

It isn't.

But then, I'm not carrying heavy loads or towing a trailer.

[JWG223]

Originally Posted by Hemlock140

Modern fuel injection engines with computer control compensate for elevation, you have no worries unless you buy something 30 years old.

Only partially. They are still losing power. They just aren't running rich or lean.

Wallace Racing - Braking HP Loss at Altitude Calculator

OP is considering a 178bhp vehicle (at Sealevel)

OP is taking this vehicle to an altitude of what, 8K feet? So....


OP will have a 136hp vehicle, at that elevation.

Turbos go a long way toward fixing this, they just run hotter as they work harder to attain the same boost at higher altitudes, so you get more heat soak.

[JWG223]

Originally Posted by Old Gringo

I doubt it.

That would mean 21% to 27% which would be very evident.

It isn't at all evident.

It's accurate. It's raw physics. Air is thinner, engines are just big air pumps, you aren't turning any higher RPM obviously, so guess what? You're pumping less air/fuel through your big air pump. There is no way your naturally aspirated engine will bend the laws of these physics, I hate to say, and yes, your Forester is likely noticeably slower. Here is how slow they are at 1 mile elevation:


https://www.youtube.com/watch?v=eWFCmcX75u0
(skip to 4:45)

It pulls a 0-60 of 12.1 seconds or so. That's at about 5K feet. At near SL, it's a 9 second 0-60, roughly.