31 replies to this topic

[J0E]

3.  Fact:  The turbo, at 5300ft is trying to take air which is already at a lower atmospheric pressure than sea level, and compress it to say 14psi.  Therefore, the turbo is already working harder to compress it.  More importantly, the energy that the turbo is putting into compressing the air is SIGNIFICANTLY raising the charge temps in comparison to air at sea level because it is applying the same(actually more) energy to compress it and the air has a lower heat capacity.  Simply consult adiabatic charts in any thermodynamics book to see what I am talking about.  This is no doubt having an impact on the efficiency of the turbo.  I am not quantifying, just saying it is.

You are absolutely correct, however I wouldn't put such an emphasis on the "SIGNIFICANTLY".

You and Dana bring up great points, but the fact is regardless of the air pressure at altitude, in the end, you still have the same manifold pressure (boost) as at sea level, or even 2000 feet below it. The only difference is the turbocharger will have to work slightly harder (pressure drop) to make this boost. However, this is easily offset by lower ambient air temperatures; in Dana's case a chili 50 degrees. That ambient temperature easily makes up for the increased temperature of the compressed air, this making the case somewhat moot. Now NA cars do not have means of compressing their inlet air to a pre-determined pressure, thus they face the consequences of lower performance at altitude. While the performance loss for a NA car is significant, the loss with forced induction is not nearly as bad whatsoever.

[kenhoeve]

No, re-read my post. All of those items make a difference and the only one you addressed is charge temps.

50* air as opposed to 80* is by my super formula, a 30* difference. I promise you the charge temps increase from compressing 5300ft air as opposed to sea level at those temperatures will more than make up for that 30* difference.

Can someone provide with a compressor map?

[Dana]

There.

-Dana

[Dana]

in Dana's case a chili 50 degrees.

Today the weather in Albuquerque at 2 pm local time was:
Temp: 60.1*F

Chili? Red or Green?

-Dana

Edited by Dana, 14 April 2004 - 05:57 AM.

[donstruke]

I have a 1985 Dodge Omni GLH Turbo that is essentialy a Shelby GLH-S clone. At Albuquerque Dragway my best time ia a 14.10@100.6 on 15 psi. It just so happened that I had to drive to Los Angeles the week following that run, so I took my Omni and went to the strip in Palmdale (2800 feet) with a bunch of friends while I was out there. Running the same 15 psi of boost I was able to post a 13.54@105.7.

-Dana

Unless both runs were in similar temp and humidity, I don't think you can compare your ABQ apple with your LAX orange. Also both dragstrips would have to have the same degree of drop/rise from start to traps. HOWEVER this sure is one entertaining thread!

[EricF]

Y'all retarded.

Did I already argue in this thread? Probably. I'm retarded.

[jross]

Interesting fact to keep this all in perspective: almost all major scientific innovation was driven by personal conflict and arguements (so Joe does serve a purpose). Newton and Leibniz, the creators of calculus (who independantly formulated it, using different notations), Lavoisier and Priestley drove forwards chemistry by leaps and bounds (Lavoisier basically founded chemistry as a modern science, and not merely a subsect of alchemy), Darwin and Owen in biology and evolution, Tesla and Edison (AC current vs. DC current), the list goes on and on. (If you're interested, one good account is Micheal White's Acid Tongues and Tranquil Dreamers. I find it's a good starting point.)

The reasonable man adapts himself to the world: the unreasonable one persists in trying to adapt the world to himself. Therefore all progess depends on the unreasonable man. -George Bernard Shaw, Maxims for Revolutionists

Edited by jross, 15 April 2004 - 01:59 AM.

[Playboy]

The temperature was around 50*F, but there was this dammed, bitter cold 25 MPH head wind that was killing everyone's performance. Going down the track and then hitting a brick wall as the wind kicked up was no fun

Yeah, that might slow you down. But at least you didn't get my performance last night:

Me: "Where is everyone?"
Them: "It's good friday."
Me: "And..."
Them: "We're closed."



A 25mph head wind could make a big difference, though. We'll have to wait till next time for your real times.

where do you race, englishtown?

[jester1182]

despite not reading even half of that ive got to say those times dont seem quite right. before you go to the track again make sure everything is in tip-top shape. youd be suprised what a little restriction or leaking vacuum line can do to crimple performance(i know i was).

[Dana]

despite not reading even half of that ive got to say those times dont seem quite right. before you go to the track again make sure everything is in tip-top shape. youd be suprised what a little restriction or leaking vacuum line can do to crimple performance(i know i was).

I've replaced all the ignition components, it boosts well and I've checked all the vacuum lines.

This track is at 5300 feet, there is nothing wrong with my car. It runs strong and hard. It is faster than a new Mustang GT and many, many other cars. The altitude affects my performance quite a bit, so my numbers are right in line.

That is all.

-Dana