bigs

Here's my baby - gonna be down in Dallas next week.

We're at 4K feet here in Utah. Dallas will be much lower. I know the basic formula for HP loss due to altitude. My question is: Will I notice a distinct "seat-of-the-pants" difference when I get down there?

Anyone have experience comparing a GTS's performance at significantly different altitudes? Will it be a "Holy Crap!" moment or an "eh" moment?

zoltan944

It will be an "eh". If you ran a 1/4 mile at both locations you would see some difference but the car really wouldn't be that much different to the butt-dyno. Also is will be hot and humid in Dallas, so it wont help as much as a 60degree day at 0feet along the beach

Sailmed

Hey Bigs,
I can't tell ya about above sea level differences.....




But I can tell ya they don't do well below sea level.

bigs

Sounds like a "holy crap!" moment...

Sailmed

7 feet of salt water came over Marathon - 20+ structure fires in 48 hrs. We were pulling fire hose down US 1 with jet ski's. We saved people from roofs, were busy doing swift water rescues - loading people and pets into the engine as they were being swept across the island, and not one of us on the department had time to protect our *** - ettes.
While non of us would wish it upon anyone, we are a strange crowd I guess - we were all having the best time of our life!
That's the engine in the avatar - 5 years later

Jack Riffle

" who's da u-boat commander"? Guess we found him!!

jpNcos

I don't think you will notice to much difference from 4k feet, but you will be a better drinker at sea level.

S4ordie

Not much difference to be noticed between 4,000 asl and being down at the beach. The computer/maf/o2 sensor/..... are always ampling the air and adjusting fuel mixture and timing accordingly. What makes a bigger difference is a significant delta in temperature.

50f at 4,000' will make the car seem much more powerful than being in Dallas on a 105f day.

bigs

That wouldn't be hard!

dr bob

You'll notice sharper throttle response with the altitude change. Max power will improve. Your foot won't be as tired from pressing against the return spring so much. Reality is that you'll adjust subconciously, and won't really notice unless you are in the hard-throttle habit. I set the cruise and can't seem to see any difference.

jorj7

Bigs,

You loss about 12% at 4000 ft, so you should get that back when you get to sealevel.
If your car has 345 hp at sealevel, you lost 41.4 hp up there. You should be able to
feel 41 hp, but since you gain it gradually as you come out of the mountains, you may
not notice it.

Nicole

My car felt sluggish in the Rocky Mountains, on the way to the Denver OCIC. Once back in the Bay Area, it was back to its old self.

jpNcos

Denver is 5680' so a little higher, and yes you will notice losing it more then gaining it from my experiences.

Ketchmi

We took Nicole up to about 11,000' while she was here, that'll suck the life right out of most 928's.

Bigs does have a bit of a hard-throttle habit, he will notice the difference I will guarentee it. I can see the grin on his face already...

S4ordie

I restate with a bit more caveat; the air temp delta in a relatively normal, spirited driven, not WOT for extended periods of time, will deliver a more noticable effect due to significant ambient air temp than air amount of O2. The metering and compensation truly moderates the noticable seat of the pants difference. If Bigs' GTS were carbed he would notice the 41hp difference in a significant way because there would be no metering/adjustment taking place. The fuel/air/ignition would be the same at altitude and sea level. Depending on how the carb was jetted would create the real difference in performance.

George, your application of WOT high output use of your car at altitude during an ORR would undoubtedly see a difference on the guages but probably not so much in a stock, unmodfied, car like Bigs. A very hot humid 105 degree F in Dallas, on hot soft asphalt, will not feel like there is a real world performance gain compared to a 50 degree F cool dry 4,000 asl mountain road environment.