Cary,
The only way you will know if the front diff is overheating in your setup is to run some stock temp readings on another car then look at yours. If there is a delta between the two you will want to add a cooler to the diff to try to help combat the temps. That is still no guarantee it will hold up in time. As to a definite answer, I apologize. I don't have one for sure. I could only start to answer based on some testing .

 

Stephen,

I will vouch for the DynaPack guys and I am not compensated for doing so. John spent a good deal of time with us and they are well informed. The New Zealand crew is also very helpful. We like our DynaPack.

The main reason I post is the back up data for the original purpose of this thread. I haven't seen it posted.

Is the supporting data going to appear? I'm curious.

Bill
MastroWRX.com
Mastro Subaru Inc.
Tampa FL

 

Bill,
I agree, DynaPack is in the upper crust when it comes to dynos. The issue is not one of whether it is or isn't. It is one of whether it is safe on a Porsche AWD. Porsches system are unique and can not be compared to other systems. It can't even be compared to previous TTs. I have talked with the owner who had the damage to his car and he is unwilling to get involved for many reasons.

 

Hi guys,

Sorry for the delay, I've been out sick for the last few days.

Actually, Scott (from our office here) called Stephen directly and had a pretty good conversation. At this point, we are thinking that this test wasn't done on a Dynapack, but on another dyno. It was supposed to have been tested in the LA area - which is only two possible Dynapacks. The first has never had a Porsche of any type on it, the second, has had several 996's with no problems at all. So at this point, we are still wondering where this occurred. I still have not received the video - but that would clear it up pretty fast. We have spoken with every 4wd Dynapack owner in the USA and Canada since this all started - every one of them says it didn't happen on their dyno. Regarding APR, they were one of the people we spoke with who said that they have run several 996's with no problem - tiptronics included. They were the one that said that had "close to 100 runs" on a customer car. Meridian Automotive Design in LA was another that has run them, so was Mastro, and many others. Literally every single 4wd Dynapack owner has been contacted.

In regards to wheel speed differences, we hold the wheel RPM to less than 2 RPM variation on all corners. This is done with optical sensors and very fast acting hydraulic load control. Some people have said that the 996 system is "very sensitive", but I don't think that there is any way that 1 or 2 RPM is enough to cause a problem. Porsche just wouldn't send out a car that was this weak. Driving it in icy or snowy conditions would kill it if this were the case.

We did some research and found the following RPM variations with these OEM spec tire combinations. All tire info was gotten from Tire Rack. All tires are 225/40/18 front, and 295/30/18 rear - factory Porsche spec as per the Porsche website.

Tire RPM @ 60MPH Variation 120MPH
Front Rear RPM Variation
Pirelli P-Zero 801 826 25 50
Continental Conti Sport 827 825 2 4
Michelin Pilot 832 829 3 6
Michelin Pilot Sport max 832 821 11 22
Yokohama AVS 829 826 3 6
Mich Pilot Sport Cup Comp 833 834 1 2

As you can see, the RPM deviation front/rear is often more than 2 RPM - in the case of the Pirelli, it is 25RPM, and 50 RPM at 120 MPH, so our 1-2 RPM deviation isn't going to cause a problem.

At this point, I can say with complete confidence that this problem did not occur on a Dynapack, and has never occurred on a Dynapack in the USA or Canada. According to our New Zealand office, they have never heard of it happening anywhere else in the world either. I know you guys want me to "prove it won't happen", but it's kind of hard to prove a theoretical negative. All we have been asking for from the beginning is when and where it happened - which is still not known. I understand that the owner may not want to get involved for various reasons, and that's fine. But the info could be e-mailed directly to us by Stephen or Sharkster and it will be kept confidential. Upon receipt of the info, all I will say is either, yes it happened on a Dynapack, or no it didn't. Nothing else will be said. Please let us know so we can put this to bed once and for all.

Thanks,

John

 

Stephen,

If the Porsche has "Power .. shared between the front and rear wheels by means of a multi-plate viscous coupling" (from the Porsche website), how is this different to a Nissan Skyline GTR which also has a viscous plate diff to apportion the 4wd (albeit controlled by g-sensors via computer)?

Not being antaganistic, just serious, since my 700bhp and 1000bhp Skyline GTRs and hundreds of others have done thousands of runs on a 4wd Dynapack Dyno here in England, without any problems. Even Nismo in Japan (Nissan Motorsports) used them on the 4wd Skylines.

John,

Having had to do dyno runs with 5 people sat inside the car and trunk to keep the car on rollers, I can safely say I would never run any big-power car on any dyno other than a Dynapack. Your product is much less scary......

Guy

(Just an owner of some cars and not affiliated in any way with anyone).

 

Wow, it looks like the tire data doesn't look like it did when I typed it.

After each tire type, the first number is the front RPM at 60mph, the second number is the rear rpm at 60mph, the third number is the front/rear variation at 60mph, the fourth number is the front/rear variation at 120mph (double the 60MPH number)

Sorry it got messed up.

John

 

You guys will have to help me here with the difference. My knowledge of the Skyline is very limited. About like the access to them here in the US. The Porsche front diff is not computer controlled or even serviceable for that matter. It uses a multi-disc setup with each layer being separated by silicone oil. The amount of oil and access to the clutch is denied. The silicone is sealed as one unit and not serviceable. As the system sees a difference between the shafts it causes the fluid to pick up heat and friction. This in turn will couple the disc. Keeping in mind that they never touch, it is friction alone that locks the disc down. The overall allowable control is 5 to 40 % max.( I thought I read somewhere that the Skyline was able to control through design 100% ? Sorry if this is wrong. ) If the unit is pushed beyond the limits the unit is sealed and the fluid gets hot enough that is causes the disc to explode and tear the dif apart.

So while the early diffs on the C4 where slave activated through the PDAS the 993TT no longer used that method. The 993TT had the Coupler in the tranny, but also carried other issues, like bent input shafts and ripped splines from the front diff. The 996 was completely redesigned, and with that comes new problems.

 

John, while I appreciate the apparent sincerity of your reply, it is almost inconceivable that Sharkey could be wrong about the make of dyno that ate his diff. He doesn't want to comment because of a pending lawsuit is my guess. Any comments from either person?

 

Hi Guys,

Sorry I didn't really want to go through all of this, since it's been stated that I was "obviously making this up"... I really have nothing better to do than make **** up, that's for sure. I've been down this road once before but just to re-iterate, I never actually said it was a Dynapack. What I did say was it was NON-mechanically linked AWD Dyno (you know there are others like Dynojet etc..), which works on the same principle as the Dynapack stuff. What I will say is if anyone wants to try their luck going on a non-mechanically linked Dyno then be my guest. I'm just letting you guys know that from my own experience and others for that matter (who shall remain nameless) it's a very bad idea and a risky one. I don't care how great the software is, if you vary the RPMs front and rear, pop goes your front diff. And yes I do have a video of it doing just that.

The only kind of dyno that worked for me was the AWD Mustang Dyno at GIAC. When I say worked, I mean it didn't do any damage. There's obviously a lot more to dynoing a Tiptronic 996TT than meets the eye Mr Dynapack. I tell you what, you show me a video of a 996TT Tiptronic on your dyno and I'll show you mine. I'm sorry but until I see/hear a 996 Turbo Tiptronic run on a DynaPack without breaking I'm not going to believe any of this. I'm sure if works great on other AWD cars but just let me know how many Tips you have personally seen done on the Dynapack?

As far as the location? Well I'm not going to sling mud at them. I don't blame the dyno operators and I'm not interested in getting them fired.

 

Thanks Sharky for the clarification. John, it sounds like you are off the hook on this one but some are still leery of your approach. I'm still watching and don't intend to do dyno work until next winter when I go to stage 4GTR.

 

 

Sharkster,

You said it was on a dynapack in your first response to this thread.

 

Ech.. that I did?!? Well there I am indeed at fault/busted. I meant to say DynaXXXX...

 

John: My apologies too. Sharky, tighten it up bro, I backed ya!

 

As far as what the dyno "sees" is there any difference between a Tip and a manual? I understand from Stephen's explanation that the 996tt system is different from earlier systems.