ttAmerica RoadsterAWD

Can the VC be changed out with the tranny/engine in place? I peeked under the car and looks like i'm gonna have to undo the torque tube, somehow have to slide it foreward, so do I need to also disconnect the front differential...............what's the general method of replacing the VC while on the car...anybody??

Jaime

Kevin

Yes, but.... You will have to undo the front diff mounts and as you said slide everything forward and drop down the torque tube.. You have to drop the tranny and engine mounts down. I have replaced a 6 speed 2 wheel drive tail cone when everyone said that I had to remove the gearbox.. Once the tail cone housing is removed the VC is very easy to remove..

fc-racer

The RUF car was totally as it would come from RUF, spare tire in there, full weight. He does have the RUF seats though which might take some weight out although they look really heavy. He could have done much better with the ET, but he really babied it out of the hole.

Have you checked your alignment settings, maybe you're running tons of negative camber and only using 30-60% of your contact patch when the car squats and accelerates. In my 944 Turbo S, anything more than -2D would cause a lot of wheelspin in straightline acceleration.

The RUF's torque output was very smooth, felt like stock but with a lot more torque.

ttAmerica RoadsterAWD

Assuming you're asking me, yes, Ruf Dallas has done and checked my alignment a few times.

Jaime

K24madness

I am running 1 degree of negitive camber. This has been going on for a while now. I upgraded the suspension from ROW to PSS9's set on 2 and have all 6 ERP links in the rear. I also installed the gaurd LSD. I have just learned to deal with it. It is a hand full.

I have driven another 993tt that puts down the similar power but has up to 60 more fp or torque below 4,500. The power laydown in that car is more predictable.

Jean

If I can add a datapoint to traction issues, not related to 4WD vs. 2WD as such.

I am attaching below a picture from my datalogger (sorry for the quality), I will help out with the readings, the red line is the lateral G forces (scale -0.4 to +0.4G) and the black line is speed (scale 55-105mph). The whole run is 5 seconds.

This is a run in 3rd gear at 0.9 Bar, hot day, dry pavement and "R" compound Pilot Sport Cup 315s in the rear, -2 degrees of camber and about 700-1000 miles on the tires..

Notice how the car is pulling sideways between 60-90mph with a peak of 0.39G. Typically you would see lateral 0.1G MAXIMUM in a normal similar run with a car that has grip. In case you wonder, 0.4G is a very very scary number when you are in straight line acceleration at somewhat high speeds. I added the longitudinal acceleration which is the green line, and you can see how it drops while the lateral Gs are increasing, depicting traction loss (over and above the normal drop in acceleration). The green scale is -0.7 to +0.7 Gs

I go through similar issues up to 5th gear and have to lift off occasionally to avoid the car from snapping at 130mph.

Any suspension issue is ruled out since I have an almost race setup, Sport Cups take a long time to warm up, and in the meantime they provide lousy traction. With my Pirelli P-Corsa, I see a maximum of 0.3G of lateral slip during a similar acceleration run.

Stummel

Jean,

0.4 g lateral is more than anyone needs to have some fun in the straight line.
I assume that your car has plenty "down force" for traction so it seems that you should live with that and master it.

BTW, how much g's is the car pulling forward in 3rd? Do you see 1g?

Jean

Stummel,

It is fun on a track but you need a desert 6 lane highway to be at peace on the street . I see longitudinal 0.7G consistently (no spikes) in 3rd gear.

Rob 97 993c2

jean - i find your datalogger graph fasincating. But, im not fully sure im understanding 100% of it in the context of the 2-wd setup vs. the stock awd. ... beyond that your car is an amusement park ... sorry that im so ignorant.

Conceptually, i agree with you that the stock awd doesnt work well, as ive had lots of problems (despite many alignment setups) getting my car to handle well on the track. Even in stock form (with pss-9) i feel the awd working against me. This makes me rethink doing turbo mods if the problem increases given the added hp/torque.

Jean

Rob
I agree, which is what I mentioned in my first line. This was rather in response to the post about the RUF not braking traction, and K24Madness saying he does.
I do think the 4WD is worthless too, especially on a dry track since it adds an unpredictability factor when you are driving at your limit. On slippery surfaces, it does help however. The sharpness of the steering , turn in and exit, are improved dramatically IMO.

viperbob

I agree 100% Jean. It is hard to explain to people the difference when you have added HP and driven the car aggresively on the track. My car was truly dangerous before taking out the 4wd system. Turn ins at speed were difficult to initiate consistantly, getting down to the apex under many conditions was tough without having to scrub off too much speed fighting the car, and it goes on. No amount of suspension tuning could get the car to handle properly (and I know a couple of things about suspension and had a full Moton setup) Now as you say, it was sharp and precise.

Peter S 993tt

I've been reading this thread - and I think I remember that the front wheels have a slightly smaller circumference than the rears (the rubber) - that differential causes the VC to heat up. I agree that if you just get in with the car cold - it won't do a thing, but drive it a few miles and the VC is quite apparent - especially in the wet. FWIW - my car doesn't touch snow or ice so I can't tell you about that.

AndyT

What type of data logger are you using Jean ? I was looking at a Raceteck system.

Jean

Andy
These graphs are from the very versatile Race technology AX 22. I also have a MXL Pista on board that is a more professional tool, but a nightmare to setup with all the sensors.

AndyT

" Excellent Smithers, excellent"

Thanks Jean I'll check that out, Andy