GDM Z28

iTrader: (16)

I wasnt sure where to put this so i threw it in here....if its in a bad place can a mod please move it?

Which do you guys is worse? Some has told me Stock LS'1 are running high 14's(@ like 103) in denver stock where plenty are hitting low 13's here (a buddy went 12.8 @ 109 with just a lid and muffler)

Can someone please tell me which is worse and why? I know the altitude will affect performance because there is less air so the motor will run rich but what if you just tune it to run back at a normal A/F? TIA

TAQuickness

iTrader: (28)

altitude has a more dramatic effect on air density than humidity.

P Mack

iTrader: (6)

That's not true, although it was with carburetors. You lose power because there is less air to burn and expand against the piston. An engine makes a certain amount of power at sea level pressure, exactly 0 power in a complete vacuum, and somewhere in between at altitudes in between.

GDM Z28

iTrader: (16)

But have you heard of LS1's looseing THAT much power in denver where it would run a low 14 to mid 14 @ 103mph? He said the autos and sticks were doing it.

P Mack

iTrader: (6)

Yeah, I believe it. I used to live in Colorado Springs. I think my cam/headers car put down like 295 rwhp uncorrected. The density altitude was around 8000ft if I remember correctly.

Also to back up my claim that fuel injected cars don't run rich at altitude, i drove my car up pikes peak (only to 10000 ft) while logging with hptuners. Driving to Texas the next day i logged again. From 10000 ft to 600 ft above sea level my fuel trims didn't change noticeably.

Ryan02SS

iTrader: (3)

I've talked to a friend from Boulder and his 435rwhp LS1 has trouble trapping 115mph at 8K+ altitude.

GuitsBoy

iTrader: (4)

My folks have a cabin in upstate NY at 1600 foot altitude, and I can clearly tell the difference in power when I take the car up there vs. driving it here at sea level. The car feels like it cant get out of its own way, even though the temps are always 10 to 20 degrees cooler up there.

org

The difference is in absolute manifold pressure. Standard sea level pressure is 29.92. You lose about an inch per thousand feet, and the effect is fairly close to simply restricting the throttle opening by that amount. That's why you can get by with less octane at higher altitudes...the engine thinks you're at partial throttle even when all the way to the floor.

P Mack

iTrader: (6)

My car pulls harder in 3rd here than it did in 1st in colorado springs.

Mr. Luos

iTrader: (9)

Last time I ran it was 8200+ DA at Bandimere. In April.

14.0 at 105.23. Cammed and bolt-ons. Corrected dyno was 376 RWHP. Granted the 60' was horrible thanks to a really bad stock clutch.
Corrected for altitude alone...13.0 at 113 (roughly).

Yup...sucks racing here. Most n/a cars find 1.2 seconds when they are near sea level.

purple98haz28

iTrader: (5)

lived in denver and now i live in south louisiana. altitude has a ton more effect ont he car then humidity. A TON

ssheets

iTrader: (1)

There was a great artcile im Motor Trend a few years back. It had a good formula to calculate the loss. It is substantial. I live just under 5,000 ft and when I drive to sea level it's play time.

Denver is about 5,200 ft above sea level...hence the "Mile High" city.

algws6

iTrader: (3)

in my WS6, i went from trapping 122 in Waco to trapping 117 in El Paso.

TAQuickness

iTrader: (28)

The PCM is quite well aware of when you are at WOT or PT.


Density Calculator:
http://wahiduddin.net/calc/calc_da_rh.htm

GuitsBoy

iTrader: (4)

Theres just less cylinder pressure with a lower MAP, so you can get away with lower octane.

Mr. Luos

iTrader: (9)

My town north of Denver is 5400, Denver is 5200 roughly, and down south there are towns that are 6000.
Bandimere is actually on the side of the foothills....at 5800 feet. Sucks. Most days are 8000+ density altitude.

It apparently effectively lowers compression ratio as well. I have heard right around 0.5 points. Never actually checked this out though.

All I know is my Trans Am was a completely different car when I took it out to visit family in Iowa.

DanWS6

iTrader: (5)

On the one hand I'd like to take my car somewhere at sea level just to see the difference but then I'd probably be sad everytime I drove it up here again.

When I went to Bandimere my best run stock (with a lid) was around 14.6@97.5

I'm hoping to hit high 13's with new tires.