..........................

 

did you prove something??

 

More than you realize, apparently.

 

This isnt the part that would protect the motor is it? Because that has to be out of the question. If it's not, then more details please.

 

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Tried it before.

 

Ah...I didn't realize that. Well, instead, you can try doing what I do with the majority of your posts. Just skip right on past them.

 

I agree with all your points, there is no perfect setup for any car, every driver, track and weather conditions can make a bad setup a good one , and viceversa. It is enlightening to see how after many many hours of setting up their cars and testing/datalogging during the two days before racing, the Supercup teams end up having to redo everything all over again the night before the race just because the rubber on the track from the F1 cars (They race and practice the same days) has screwed up everything. In Supercup terms, that means for the driver being a tenth of a second slower.

Sorry but I cannot see how this is possible.

The 62-38% weight bias on the GT3R cars is impossible to get anywhere close to 50-50%. That would mean moving around 260lbs from the rear to the front of the car, which in Cup car terms is literally impossible since there is nothing to move. In fact I don't know of any Pro- series that would allow moving anything rear to front or use components that would skew this weight balance. Some change can be had by playing with fuel quantity, but this is very limited.

The 996 GT2 has a weight bias of 63-37+ vs. a 996TT that has a 61-39. The 2% shift between TT and GT2 is as a result of tire sizes, and AWD components namely. In contrast, a 997 GT3 has 61-39% and a 997TT has exactly the same 61-39%. The 3 year winner of the German Tuner Grand Prix, the Cargraphic GT3 RSC, has a weight bias of 61-39% and so is the Manthey M700 Nurburgring beater.

Going to 50-50 is a moot point given the design of the cars, whose geometry was built around this weight bias and any changes to it will make the handling worse rather than better after a certain point, IMO around 3-5% maximum, after which no suspension modifications can make it handle better.

Back to the thread topic, getting the right balance for a 2WD is not a difficult thing to do, exactly just like getting a 4WD properly setup for the track IMO.

 

change out the front carriers and add lower GT arms and increase neg camber. loosen up the front sways. take out excess weight up front. this will help understeer. oh yeah, and a good corner balance.

 

"Jean"

We have run 50/50 on our 996GT3 WC car -although be it with ballast. It is fully attainable. SCCA mandated and minimum bias for the Porsche's.

Every engineering has there own opinion on what weight bias and what works best.
We found what works best for us based on the conditions we race in.
There are so many variables based on set up that we can sit here and debate for months.

I can also tell you what teams "publish" there weight bias in these (tuner challenges) and what they really are often times completely different.

Anyways......... back to the thread..

 

Fabryce,

Since you had mentioned Pro racing, I was referring to IMSA Cup racing rather, just realized that you race in SCCA WC (as well). The 100% factory stock (by regulations) Michelin Supercup cars running at Indy with factory ca. 60-40 weight balance/bias were running fast laps of 1:35s last year by Alzen and Saelens, I am not aware of any private team owned and modified Porsche GT3 race car going faster.

However if it is SCCA that you are referring to, I admit that I am not very familiar with the regulations, but if I am not mistaken, the base GT3 weight is 2900 lbs, which means that you would need to shift about 300lbs+ rear to front to get a 50-50 balance, which is even more unlikely

Also, maximum ballast in GT is 200 lbs (please point me to it if I am wrong), and must be placed and strapped in the passenger footwell/seat area per regulations, so other than needing 300 lbs to get to 50-50, I honestly don't see how this location could make much difference to weight bias with 200 lbs max, but if you are sure about your numbers, I will not dispute it further.

I am not trying to debate for the sakes of it, but I fell it is important for people to know that there is no point in going mad over achieving those 50-50 weight balances when in reality it will not make much difference but rather maybe the opposite (due to suspension geometry). In a racing environment, it is mass transfer that really matters, and that has little to do with static weight balance. Unlike daily street driving.


Tuners competing at the German GP are required to have their cars officially weighed prior to the event by SportAuto the organisers, in the particular case of Cargraphic, my information is first hand from Cargraphic owner.

Cheers
Jean

 

Jean you are certainly the statistition

Yes I do agree with you on some points ... When refering to Speed GT I was refering to years past and not the current rules as SCCA will change the rules
to keep the competition equal.

All things being said. I have been around racing long enough to know the games teams play.. We sometimes play them too

In terms of the of the set up and weight bias.. Everyone has there own opinion what works and what doesnt. I was simply speaking from our experiance at that particular time.

You should come out and do some racing over in the states. There is always a need for someone who knows what they are doing in practice versus just in theory..

Are you currently setting up cars and doing any racing?

If you are ever in town please feel free to stop by..

 

Fabryce

I understand.

I don't like statistics (with due respect to Wross). I believe in practical and accurate data.

I first raced as an amateur a car 21 years ago and use data as an edge as I don't have time to practice enough.

I am also lucky to have as a close friend and mentor an engineer who is paid to advice top Michelin Supercup teams and also people like the Bergemeister brothers what they do right or wrong.

Thanks for the invitation, I will sure drop by whenever I am around .
Cheers

 

Forgetting about aerodynamic downforce, the only time a 50/50 front/rear weight distribution is "perfect" is in steady-state cornering, on a car with equal sized tires. When braking - even into turns - a rear weight bias offers a slight advantage because forces are more evenly distributed to all four tires. When accelerating, a rear weight bias is also advantageous because more weight is over the primary, rear driving wheels. Do formula cars appear to have this imaginarily perfect 50/50 weight distribution? I don't think so. The perfection of the 50/50 is in the imaginations of ignorant automotive journalists, and the marketers of front-engined performance cars who can't hope for much more. Of course, once you put a huge wing at the back of a
race car, which may generate many hundreds of pounds of downforce, your static distribution is suddenly less important, and your dynamic distribution, at least for going fast, will have a rear bias.

 

By "push", you guys mean turn out understeer, not turn in, correct ?

I don't think that this is necessarily a weight distribution issue per se, Ferrari V8s are around 58/42, but the *huge* difference is that the weight is between the axles, not beyond them, so they don't squat as much under load. Don't get the motricity either, but once you've nailed the apex, you have the guarantee that the front will not wash out, like 911s tend to.

My Carrera was horrendous in that respect, the TT seems better in that respect. The most telling corner I know here in that respect is turn 6 at Infineon. I find Thunderhill quite forgiving in that respect.

 

You hit the nail on the head with that one, sadly some of the people here that are commenting about having resolved push have not tested it in real conditions that bring out the flaw. Turn in push can be eliminated with a rear sway, but track turn out push is another issue and once the sway is added, something that DEFINITELY cant be tested on the street (I've tried it and nearly crashed doing so) And it can only still be tested on certain turns at certain tracks.