PrivateParty

In my 96TT, I am running around 625-650+ HP and torque on average and cannot keep a VC in it. After mods, the stock one went pretty quickly and I had a "stronger" one put in and it made it less than 1,000 miles. I want to take one last try before converting to RWD for good so I am looking for a VC that will handle that power without problem. Stock tires/wheels, and weight and it is almost exclusively used on the street. Thanks in advance for your help and suggestions.

RallyJon

The rumor is that the 993 C4/TT VC is out of the Subaru parts bin. Never confirmed it, but it looks awfully similar. Have to check splines, etc. But if it did match up, or was easily adapted, you'd have many options.

sfbanchs

what setuip are you running to achieve this type of hp? Are you doing hard launches. The VC should be able to take it

PrivateParty

It is a Vision Motorsports (Orange County, CA) project car that they then carried over to their race cars. Lots of stuff done to it and a lot of it custom made by them (Kokeln). I do not do hard launches but once it's moving, I will go. It will easily spin them in 2nd if you hit it and I am not happy with the 2WD so trying to get something figured out before committing to RWD only. The last VC was the "strong" one from California Motorsports but that is all I know. Maybe it is something unrelated but we are currently at a loss.

911/Q45

Try using R compound tires to minimize wheel spin. If you go to larger sizes, maintain the F/R diameter ratio.

PrivateParty

Well, actually, if I leave it as is, I guess I can go any diameter I want as there is no AWD. I can go R compound but I'd like to try AWD one more time so I would like to try to find the VC that will handle it. If I can't find one then I will make the RWD move completely and make some big adjustments. I have seen the thread on RWD vs. AWD (And have my own opinion) but would like to try it one more time as AWD if I can do it.

Carrera GT

I wonder if this might be your culprit. I've seen 993's with at least 600 hp that did not eat couplings. Perhaps you've got an unintentional gearing problem that's accentuating the load to the fronts and overworking the coupling.

Anyway, I'll spill another of my genius ideas that surely is a real money maker idea that I was considering when I kept finding dead couplers on Turbos and I hadn't yet thought through the 2WD conversion.

The "Coupler Cooler." Take a cold-side oil line in an air/oil 911 and route a new segment around the coupling, then back to the radiator with a flow valve to ensure this never starves the engine cooling. Hey, presto, almost no matter how much heat is generated in the coupling, it will be drawn away by the coolant. I'd suggest welding the coupling to envelope it in a "bath" but I'd probably start just by running coils around it with maybe some (very thick) copper alloy or a good conductor to make sure it's an effective heat sink thermal connection.

I have no clue on the operating temperature range of the fluid in the coupling, but I've seen the casing turn blue as if it was 1000+ degrees under a blow torch. I have to imagine Mobil 1 can take the heat.

And surely this particular car already has an auxiliary oil cooler.

PrivateParty

You might be on to something that I was wondering about. With only RWD I am noticing slip in one side of the the rear end around sharper corners so I have an LSD issue or one that needs to be tightened. That might do it. Other than that, I actually have custom carbon fiber intakes and, believe it or not, it runs as cool, if not cooler than stock with no auxillary cooler, on the street at least.

911/Q45

If you go to R compound tires with AWD, that should minimize the traction loss that is probably frying your VC.

aneckas

Just as a clarification for others, I checked with California Motorsports today and had a great conversation with Rodger. He said that he was not aware of any upgraded ("strong") VC that they ever made. He wondered if it may have been confused with their rebuilt LSD.

At any rate, they sell a lot of nice stuff but do not sell an upgraded VC for a 993.

Alex

Carrera GT

This idea of a "strong" (or stronger) coupling came up years ago. The only solution at the time was to take the VC "job" out of the "snout" of the transaxle, put it in the middle of the car, perhaps integral with the shifter assembly (making the whole thing rigid enough to take the torque through the torque tube) and have this new "central" center differential "negotiate" with the front and rear differentials. This would put it in a more "generic" housing that could then use fortified internals from other cars. Obviously not for the faint of heart! (or wallet)

You'd probably need to get to an AWD factory rally team to figure out what works -- presumably Subaru, Audi, Mitsubishi ... some of the Paris-Dakar teams? ... parts from the newer cars or the 964? Lots of research to get a picture of what's out there.

I still think it would be a great project for the high horsepower cars. For time being, I'm happy with the tail happy 2WD conversion.

BDHo

upto what hp do you guys feel the stock VC will work properly?

Carrera GT

It seems that beyond the "uprated" hp (say 425) the coupling will be overwhelmed, but it's really the torque and traction differentials -- if you beef up the torque to approach the design limitations of the stock internals (say 500-520 ftlb) and improve suspension to keep all four on the ground and increase traction with wider, stickier rubber, the coupling is going to overheat whenever the rears rotate faster than the fronts and the fronts are sticking like glue (for sustained periods, only possible on the track.)

As these cars age, I think the insidious risk is a car that goes from AWD to 2WD over time without the driver knowing that the next time there's any compromise in surface, the car might not behave as it has in the past.

Jack up one front wheel, leaving the other three wheels firmly on the ground. If you can turn the wheel off the ground without significant effort, the coupling is dead. The next thing to die will be your wallet. : )

If you dismantle a transaxle and look at the couple and it's an odd bluish color, it's still potentially fine (I think this is a combination of heat and welding during manufacture) though it might simply have died of mileage. If the thing is completely discolored, that's probably a car that was put on a 2WD dyno or was the subject or repeated standing start nonsense.

It would be fascinating to have some old timer in R&D at Porsche explain what they've done over the years in the AWD cars and talk about the backwards compatibility of the newer hardware (if not the electronics.) This sounds like an excellent long form technical piece for Excellence.

Carrera GT

You could check with Alex at Sharkwerks. He ran a drag race setup in a 996 Turbo for a couple of years and got the thing, I think under 10 seconds? Must have been a lot of torque to get that heavy bucket so quick. : )

V

Paging the owner of "Blackie". . . . . Jay where are you??