HeavyChevy

Clear, I understand. I will download the software, please send me the files.. Jean Lahoud

Just to make sure we are aligned though, the 996TT 4WD system is the same as the 993TT (996 was not the first Porsche to use it), as far as what could make any difference to acceleration is concerned. It is the 997 system that went back to the 964 model.

The only difference is the transaxle tube going to the front differential and the position of the VC to improve weight balance ratios. The VC system and mechanism is exactly the same, it is a silicone filled temperature activated power transmitter that relies entirely on the wheel speed difference between the front and rear and variable between 5-40%. Once you disconnect and remove the tube, VC and axles from the front, you get 100% power on the rear wheels, as long as you don't do that, you might have interfering electronics or other.

Your data might be accurately read on your car, but where I might disagree is that the data collected and the way it was done is not valid to state that 2WD is slower in acceleration, if done the right way, it is not, and arguably on the track as well, you do need to make substantial adjustments to your suspension settings and hardware to take full advantage of the swap.

Concerning your questions about the car, the 993TT car tested is exactly the same before and after, no changes whatsoever. It has stock gearbox, the GT2 Motorsports LSD, weighs about 3300lbs with driver. Its fastest run was a 6.9 seconds 60-130mph with 2 normal shifts. It has been very consistently running 6.9-7.2s in 2WD mode always for one year, and immediately moved to 7.6+ seconds when swapped to 4WD, same road.

I will post the 2 separate graphs now. I am trying to bring them together into an excel based graph by extracting the data from the loggers to excel. It willl take time though.

 

Here are the two graphs.

First graph shows a 7.6 seconds run on a Dbox, this is the 4WD setup. The second gearshift could have been slightly improved.



And the next is the 2WD setup 60-130mph in 7.1 secs. There is a faster run, but I took an average run. Everything else the same. As I said, there are several runs in this range, the 4WD run was automatically 0.4-0.5 seconds slower than all the others. Allowing for shift/temp, etc.. the results are quite conclusive IMO.



I can bring both charts on one graph but will need to extract to excel all the data and work it out.

 

Dez and Jean,

I have long considered this mod (although at my power level it scares me),
I am also interested in Dez's track results as it seems odd??

MK

 

Jean, what is your file size limit on your email service. The file is 11.1megs and it got returned to me.

 

I do not see what the "question" is hear or the confusion. It's simple physics, if you are a good driver the car will absolutely be quicker. Less weight and less friction means more speed

I am going to RWD next week hopefully. The 996TT is boring with the AWD

Christian

 

Marty I would not go 2WD on a high powered track car unless I am willing to put the time behind fine tuning the geometry and investing in suspension upgrades and other parts. Your driving style has to change and adapt quite dramatically also, until then, you might not take full advantage.

With stock gearbox it lapped an 8:30 at the 'Ring in its /my first ever outing in it 2 years ago which is very decent for a street car, considering it was my first time there and Todd K. had it limited at 1Bar one day earlier in Hockenheim, no LSD ...until today.. You often have 300 feet powerslides exiting fast turns, fun, but not ideal.

I now have spent many hours fine tuning suspension with the help of dataloggers and upgrading hardware (still rubber mostly though) to get it where it is now, you will also need more rubber front and rear.

I always hated the unpredictability of our 4WD systems, I would never go back.

HeavyChevy I PM'd you another address. Thanks

 

It's not that bad with the stage 2 set-up (around 425 rwhp), but I wonder how differently the car will behave one I throw on zero-clearance K16/K24 hyrbrids on there and get close to 500 rwhp. I already have H&R sways front and back and have H&R coilovers...I wonder if an investment in the LSD is the next thing...

 

It is not the HP that will make a difference but rather the torque delivery on exit, larger turbos will build huge torque within a narrow band of RPMs, and typically that band starts around 4K Rpms and 90% of the times in my case at least, this is where my revs are approx. when I exit a turn and squeeze the throttle. As long as you are with K16 based turbo hybrids, and namely K16/24.. I would highly doubt you will face issues. You can live without the LSD IMO, not optimal, but I know I do.

 

Did anyone here ever read KPV's analysis on the Turbo's inherent suspension geometry flaw when lowering the car to GT2 ride height on PSS-9's. I think it's quite informative.

I think a lot of people here underestimate the importance of having the right suspension geometry. Especially as you take the car closer to the limit, the car starts to do unpredictable things if your geometry isn't optimized for ride height, things like dynamic camber change become big issues.

Fact of the matter is that the Turbo's suspension geometry cannot be fixed simply by a proper alignment and/or a coilover setup.

Even in the GT3 world, there has been much evolution in the development of suspension geometry, especially in the front. If you compare the uprights/wheel carriers from the GT3-R, and then the RS, then the RSR, and then the various Cup variants you can see that the shapes are completely different. The major difference in handling between the 996 and 997 GT3 variants is that the latter uses the revised suspension geometry (subframe, wheel carriers, etc.) developed for the RSR, which was homologated via the 996 GT3-RS street version.

The track times reflect the superior turn-in and overall handling improvement. Look at the new GT2, which runs a purported 7:37 on the Ring. That is pretty impressive, and it isn't just the power...

The Turbo's suspension is inferior even to the GT2, so where do you think a RWD Turbo with unoptimized geometry and a "good alignment" and coilovers stands in the pecking order of Porsche RWD suspension setups?

 

Hamann7

Long time no hear from. Generally I agree, but you know guys like Cary can really transform a turbo suspension. Then again, it is no longer a turbo suspension.

 

BINGO Again, we just won't do it

 

Wow, this is still being debated? Heavy, I really mean no offense at all but this is very basic stuff. Less power loss from the front + less drag from the diff + less weight = more power to the rear drive wheels and faster acceleration (traction pending - from a roll it's no question). There is absolutely no other conclusion that can be reached, and you now have data from Jean to prove it. It is in fact, A FACT. Like the Earth orbits the sun. No sense in arguing, you just did it wrong, why don't you chalk up your losses - the misinformation you insist on is a little embarassing for you.

 

Since somone brought up the issue of suspension... lets begin with the fact that the 996TT suspensions sucks big time. Thus continued conversation about RWD conversion is pointless.

 

Tell us how you really feel. I agree

 

I don't think anyone is debating that you get less drive train/friction loss going RWD. Of course you make more power and save weight! That's a _fact_ all I'm trying to say is that too many people simple pull the driveshaft and think that's all you need to do. Granted if spin city and a more nervous car is what you're after then fine It's just the geometry, set up, brakes, uprights (I could go on) are different in a GT2 and trying to mimic it as much as possible will at least make a TT closer to it in terms of feel/poise. Having said that a 700HP GT2 and "safe" are not usually words I'd throw out there... You have to be a _very_ good driver I believe.

So back to the point I was making about my shop in general, is that I just worry about the safety of the guys that bring their car in here. I don't want to make a car that could lead to someone getting hurt _knowing_ that I had a choice to keep a 700/800hp turbo "safer" in AWD mode. I'd rather loose money if that's the case.