Jean

I see. And if you adjust your numbers by 2.5% or anything less, you will be in 0.3G territory as I mentioned.

The adjustment as you are doing it is for low speeds, since the tire will compress under the load of acceleration, however once you reach higher speeds you need to reverse that factor because of tire expansion as a result of heat and centrifugal forces.

Most likely than not your speed will be higher than 220kph at 6050RPMs, for instance, TB993TT reached beyond 200kph with 295/30 tires before hitting his rev. limiter in 4th gear, so around 7000-7050RPMs, if you do the math, it is a zero adjustment to rolling circumference at 200 kph, but I think we are splitting hairs here.

Jussi

Jean: check my ax test -topic

ebaker

Respectfully, I believe caculations of speed, power, and acceleration should use a tire's circumference and not the rolling radius. It's based on the distance traveled with each revolution of the tire, which does not change when the tire is compressed by loads. This all assumes no slipping. I don't believe the 3% compression correction factor should be used.
I also would be interested in seeing the data on all the engine parameters on your runs.

eclou

Whew, just made it through all 85 pages - took me a whole week. I have to say you 993tt guys are a compulsive bunch. Great info here. I would like to humbly add my data point - 997TT with GIAC ecu and AWE exhaust (200 cell cats). 100 octane, upper 85-90F with 70% or so humidity. Sea level, slight uphill run with no noticeable wind. No powershifting. Std weight car, driver 180lbs



100-200 kph about 7.3s and 60-130 mph about 8.4s.

pstoppani

Well, my motor is a victim of a botched attempt at getting a 60-130MPH measurement. On my third run I decided to try starting in 3rd (I did a couple that started in 4th) and sure enough, I blew the shift from 3 to 4th and got 2nd instead. I got to see 9500 RPM on the tach for the first time; and then the smoke

So far it looks like I just blew the crankshaft seal, but will know more next week.

Looks like it will be Spring before I can try it again, a bit more carefully!

eclou

looks like my clutch did not like the GPS runs. Clutch is slipping badly now.

Basal Skull

ouch, sorry to hear that guys! I guess these runs can take a toll on our cars....

TB993tt

The 60-130 should have no ill effects on a properly prepared car. The gear change is an (embarrassing ) driver error and could happen during any spirited "session".
The clutch sounds like an incorrectly specced "tune" - Tuners worth their salt will know how much torque the stock clutch can hold and will spec accordingly.

No excuses -lets have some more

eclou

It's not the 60-130 that eats the clutch, it's the 0-60 that precedes it

pstoppani

Indeed

ScottMellor

OUCH!
At my first drivers ed, I was given some brilliant advice on how to avoid the "3-2 MONEY up-shift".
When you go from 3rd to 4th, reach down with your palm facing down and away from you. With your open hand just push the gear lever back and into 4rth. The spring loading keeps you in the gate and if you completely screw up in the heat of battle, you can ONLY end up in 6th.
It really works.
Now ifI could just find a trick to keep from turning on the windshield wipers other than removing the fuse or blades ....

Jean

Compulsive? Have you been to the 996TT board lately?

Great times, these 997TTs will never cease to amaze me, excellent performance! I would look at the 60-130mph as a real life check up of the car. This test is not being rough on it (unless one goes wild), but it can show you the latent weaknesses, such as clutch, overboost, loose IC hoses etc... Isn't it better than if you had the clutch go bad during your upcoming Texas Mile?

Pete, I had this happen to me at the race track, and it was VERY violent, I released the clutch too and almost hit the wall as a result . The engine did not suffer any damage then that I could feel, however I did blow the main seal a bit later, this is the cranckase seal I am talking about. The only reason it would smoke with the seal failure is if the oil is dripping on the headers. Good luck.

eclou

That's what I keep reminding myself. Actually I am quite happy it did not let loose a couple of weeks ago during the track event. I had been anticipating the need for the upgraded clutch for some time now. At least there will be one less thing in the back of my mind to worry about for now...

BTW If interested I have a shop that can fab inconel manifolds for anyone interested. They have just finished 996/997 jigs for me, and 993 jigs can be done with a donor set of manifolds.

Bill S.

No need to start from 0. That's the beauty of the 60 to 130 test. It's easy on the car.

Start from about 30 MPH in 2nd or 3rd gear and then floor it, taking each gear to redline. Start in the gear that gives you the fastest 60 to 130. That's probably 3rd gear for your car.

Felix

Here's a 9.66 second 60-130 run with a UMW stage 2 set-up. There's probably some more time to be saved in the shifts but not a huge amount.

Speed, intake air temp and altitude are aganst the left axis while boost and longitudinal g are against the right axis. Data recorded with a Race Technology DL1.

IAT is from tapping into the factory sensor in the intercooler and boost is meaured using an external sensor.