edpurplett

Wow...cheers for the smart folks !! some backup for my 'seat of the pants' theories :-).. Thanks ALL!!!!!

6% sounds pretty close... can one of the smart folks validate that with HP to weight guesstimates..? (though I guess HP-weight numbers are mostly qtr times??)

Would 50 to 85F degrees delta, stable barometric.... support my contention that I run in the 7's in cooler weather (50 degrees plus-minus) and lose almost 1.5 seconds in 80+ degrees... (3140 lbs at 80ish degrees)..

Approx 600 crank HP at 78 degrees if memory serves.. (realatively wide and early torque curve since I know the number sseem optomistic and I havenet validated speedo to fractions yet... :-).... 500-550 ft lbs from about 3800-6500

... this all basically started since Jean's times seemed slow and I thought it was predominantly heat related.... maybe so?!?!?

e

TB993tt

Bill
CGT - great stuff

May I ask the 100-200kph time - the mags all seemed to get around the 7 second mark ?

Ed
That dyno data I posted before shows that at 30DegC ~86DegF the power lost is 35hp.
I'm afraid that is not enough to lose you a full second or more unless there is something wrong with your set up and too much timing is being pulled losing you much more.
My guesstimate is 1.5 seconds at these levels and weights represents between 50 and 100hp ?

FM9

So what is the final verdict on VRAlex's 4.4 second run.......real or fake?

As for the CGT run, it looks about right for a two person, 91 Octane run by a non-pro driver.

edpurplett

Tb,

thnx! you're probably right... I'll try to do some temps variance runs on the same roads if the AX shows up ..

e

Jean

Bill, thanks for the data, it is great value added to this thread!

Alex's runs are not conclusive as far as I am concerned, they could be correct, or they could have an issue. He does have a run that is 100% conclusive however, done at 1.2 Bar and still the fastest by far posted here. .

Now, are you going to continue hiding or will you disclose which tuner you are in the UK?

Jean

Ed,

Why are you torturing yourself?

You will get the AX22 very shortly, can you imagine what happens if you run it in 10 seconds?

My run was at 0.8- 0.9 Bar Ed with my lousy aerodynamics, huge tire drag and alignment settings , you'd better beat my times!

edpurplett

Jean,

I'm a masochist...I like to torture myself.....

I'm hosed whether I'm fast or slow in the times.... :-)....If it's 10 seconds I have to banish myself.. If I'm faster than you I can't possibly ever tell anyone since you're such a gentleman.. ;-)

e

Bill S.

7.98 seconds on our run with the .4 second shifts, 91 octane, bumpy road and 2 people.

Konstantin

this is slow for a C GT. Either something wrong with the car or with the driver or with the test conditions.

Konstantin

Jean

Well, I will show a practical example below about Bill's shifting skills, and while over a short run like a 60-130 the relevance is minimal, over a track race or longer run, the difference would be substantial. Again thanks to Bill for sharing all his data, true openness and value added in the real sense of the word.

Back to theory, as far as gear changes, the theory is widely available out there, from the practical side of things, you need to look at your dyno chart and establish the RPM band between your peak torque and peak HP in every gear, not complicated at all. Then you need to calculate where does the next shift drop you in terms of RPMs..

To identify that optimum RPM range, you simply do the following (stock 993TT):

Gear ratio 3rd.: 1.56
Gear ratio 4th.: 1.21
Identify the RPM drops between shifts: (Simplistic formula)
RPM after shift = Gear ratio to/Gear ratio from X RPM before shift
RPM after shift= 1.21/1.56 X 6,700= 5,197 RPM

So when you shift at 6700RPMs you will recover acceleration at 5,200RPMs which puts you right between peak torque (4,500RPMs) and peak HP (5,750RPMs), you are good to go.

The graph below shows how Bill's long G's during his shifts (black line) hardly drop to negative G's, meaning his car hardly decelerates while he is shifting.. Also, check out the broadness of his dips (shifts), the narrower, the faster they are.. This is comparing my shifts (green) vs. TB993TT (red) vs. Bill S.

The dips in long G's can be due also to drag (aerodynamic and mechanic/rolling) since I have the most downforce of the three cars and the fattest tires.. The table on the top left shows what the times would have been if TB993TT and my shifts had been as fast as Bill's. Imagine this over an enduro race!

JasonAndreas

The NA 993 starts to pull timing at 68F/20C, does anyone (Geoff(s)?) have the maps for a TT?

Bill S.

Thanks Jean. Maybe we'll be able to share in the new-found AX-22 profits.

Here's some Ruf Turbo R bhp and lb/ft figures (from 1998 911 & Porsche World) that may explain why Ruf suggests shifting at 7200. Numbers are rpm, bhp, lb/ft. The curve is more important than the actual numbers (i.e., area under the curve is power):

2000, 104, 267
2500, 182, 375
3000, 235, 404
3500, 279, 411
4000, 348, 449
4500, 466, 535
5000, 506, 523
5500, 499, 468
6000, 460, 395

I think the goal is to stay in the max HP and TQ area as long as possible without too many shifts. That's pretty much the theory behind the new CVT cars (Continuously Variable Transmission).

I always thought it would be cool to show, in different colors, where you were, and for how long, on the HP/TQ curve in each gear.

Here's exactly what Ruf said to me in an email:

"To get the best acceleration you should shift at the first interrupt of the limiter. To rev to 7200 rpm is OK."

Red rooster

Bill,
Do you have any more torque numbers above 6000 rpm ? Just so I can have a private look.

It certainly was not my intention to imply that you were not a very good driver.
Such a thought never entered my head .
If this harmless look at some gearchange theory is to be taken to a personal level then I apologise for posting and withdraw from this thread.
I obviously wish you well .

Geoff

Bill S.

Geoff, you're funny. I actually thought Jean wasn't addressing your question. You wanted to know the best RPM shift point, and we have a discussion on shift timing, where it sounds like I'm a bit unusual. Fortunately it doesn't take much skill to get the optimal shift point, just someone telling you!

Here's more data from the Ruf Web site. I haven't seen anything published over 6500 RPM...

Jean

Bill, as agreed in private, please lease it for 50 USD per run for cars below 9.1 seconds and 30 USD for 9.2 or above.....no! the other way around should be more profitable

Geoff, we' re just having some fun, I am just trying to "sell" the tool with some charts, seems like we have a busines going Thanks for your inputs, they are always very interesting.