MySwiss

Nice numbers Edman951. Let me know, when you on the dyno.....

porshhhh951

elevation really does effect times thats for sure.

I was stock at a 14.0 with a launch that could of been better. There is sounds like a 14.0 is fast for you guys. I am like right at sea level almost. I guess if I run 12's here thats like 14's there. lol

Edman951

Thanks Steven,
I will call you when i plan to go.
Are you going back to the dyno soon with the new intercooler?

p.s. Nice Website congratulations
Happy to see its finally up and running.

DanaT

John,

To "convert" runs at my altitude to "standard (sea level) conditions" using a rough approximation multiply the ET by .92 and the MPH by 1.07. Those are the "official" NHRA correction (or ver close to it) factors for that track.

So a 14.0@100 here would be a 12.88@107 corrected. If you want more accurate correction (i.e. like a dyno uses) you have to convert based upon temp, pressure, and humidty.

Finally, when people talk about drag strip times, I like to think of an old saying that bookies have:

"There are three horses that never win, place, nor show. Their names are Shoulda, Coulda, and Woulda."

That mean, I am not impressed with "well if my car was running more boost, I woulda run 8s". "May car coulda run 8s if the A/F was correct". Basically, nothing more than excuses. Excuses end when the vehicle hits the track. Thats teh allure of street racing. When they loose and have the excuse "I coulda beat you if my car would have been running right" the reply is "I guess you need to figure out why your car don't run so next time you won't loose the cash".

I have never street raced BTW

-Dana

rage2

NHRA Corrections don't work right for turbo cars where:

a) you can adjust boost until you hit the knock limit
b) the boost control system adjusts boost based on absolute pressure (MAP sensor).

Assuming of course your turbo can flow enough air in the above scenarios (wastegate not completely shut up top).

Assuming you are at 4000ft, run the edge of knock at 18psi (which is roughly 15.5psi absolute), and run a 13.0. At sea level, you won't be able to run 18psi, you'd be only able to run 15.5psi because that's the absoute pressure where things begin to knock. So, you'd be making the same horsepower. BUT, at lower engine speeds, ambient pressure is higher, thus, it will improve spoolup rpm. Therefore, you may get a better launch. Scenarios like this you'll see very minimal changes in acceleration, just in the initial launch.

Replace "knock" with "ECU preset absolute boost limit" in the above paragraph and you'll get scenario B .

Now, if you have a turbo where it runs out of steam, meaning your boost controller is keeping the wastegate completely shut up at high rpms, you'll be faster at lower elevations, because it'll be compressing higher pressure air to begin with, you'll get more air, and thus more power. In those cases, the NHRA corrections work fairly good.

special tool

/\
|| One of 5-6 guys on 951 forum to whom you should listen, IMHO.

DanaT

Rage,

Also, don't forget that at high altitude increasing boost changes the pressure ratio. That may drop the turbo into a less efficient range. Also by ideal gas law, as you compress the air more, you generate more heat and hence less effieciency.

The intercooler is also more efficient at low altitude as at high altitude, you have less air mass moving over the surface for a given speed (less dense air means fewer lbs/hr, or moles, of air flowing over the IC to remove heat).

Also, there is one other consideration that you must take into effect if you run "pump gas". At high altitude, an N/A engine creates less cylinder pressure. Therefore, less octane equivalency is needed in the fuel to prevent detonation. Less octane, cost the fuel companies less money.

At high altitude the fuel you can buy is 85,87, and 91 octane. 91 is "mid grade" fuel. Therefore, your knock limit under boost is the same as if you were to run mid grade fuel at sea level.

Off boost performance is not just a little worse, but a whole lot worse. I had my car at sea level for a little while. It was much faster and more repsonsive at sea level than at 6000ft. Off boost performance was in the "acceptable" range at sea level, but in the "pathetic" range at 6000ft.

It not as easy as "just crank up the boost". I have already done that.

-Dana

DanaT

Also,

As far as "corrections" go I think the are bogus in general. Why? Well I have mostly drag raced motorcycles. If you take a 10.00 second bike (easy number) at high altitude it would be "corrected" to a 9.20. There is a lot of difference between controlling, getting outta the hole, etc on a 10 second bike as opposed to a 9.2 second bike. The faster time then requires more tire. Etc, Etc, Etc. The faster you run the harder it becomes.

The correction factors are mearly an estimation at best and good guess most of teh time IMHO. It does allow some comparision to low altitude though. That is why I tell people you ran what you ran.

-Dana

daniel951

whatever i get i get so i am not worry to much because my car isn't design to drag. knowing my luck i will break something trying.

NZ951

MySwiss, I thought you changed turbo's? You still using the 60-1 HIFI?

daniel951

i thought so. i think he only changed the chips to vitesse.

rage2

Yep, but the changes are much more minor than say, the 2.2psi of ambient pressure difference between me and sea level, not enough to justify the NHRA correction factors. It's off quite a bit .

When I drove my car at sea level, I had to drop boost by 3psi. The car felt a little peppier than at 3700ft, not enough to justify like a 5 or 6mph difference in trap speed that's for sure!

I'm lucky to have 94 octane at the pump here at 3700ft. Funny you mentioned 85 octane, I was going to ask you about that seeing as you were way up there in colorado. I heard about it but wasn't 100% sure.

Here in Calgary, I always recommend people to drop 2 octane points for NA cars because it's a waste of money, plus it'll improve fuel economy. Manufacturer recommends 91, use 89, it'll perform better.

DanaT

I cranked my boost upto 19 to see what happens

I will have to compare times to when it was running 16. At 16psi I was running 103mph traps.

Must get the car on teh road first though. I was hoping to get a package of parts in the mail to finish the A-Arm rebuild (wanted the 968 camber blocks). As soon as theyare in, I can get the car on the road.

Yes, I don;t agree with NHRA numbers, but I have seen the turbo cars running slower here than at sea level. I think times are more affected than MPH.

-Dana

Dark Lightning

In my experience:

The elapsed time is primarily the result of 1) how much power you have, 2) how well you can shift, and 3) how well you can launch.
The trap speed is primarily the result of 1) how much power you have and 2) how well you can shift.

You can bog the launch for 15 minutes and still have the same trap speed so long as your shifting is consistent.

daniel951

what do u have done to ur car dana