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Is it safe to put a 996tt on a RR?

Boony

Member
Joined
28 Apr 2007
Messages
7
Got my 996tt booked in for a power run on a local rolling road tomorrow but just wanted to check it's ok? It's a 4wd rolling road so no issues there, and I guess since the 996 is water-cooled with rads at the front, it should be fine?

Also, anyone any idea what transmission losses are expected on the 996tt?

Cheers,
Boon

Migration info. Legacy thread was 138743
 
The correct way to RR a C4S/Turbo is to disconnect the propshaft and run it in 2wd, in 4wd the viscous coupling will constantly divert power front to rear to front, the Turbo will possibly try and throw itself off the rolling road.

I ran my C4S a couple of years ago in 4wd mode on a Dyno Dynamics dyno, this had a 400bhp 4wd limit and the car's ABS/PSM and viscous coupling had the car bucking endangering the car and the dyno.

I'd take care! But do your research and make your own mind up.

Migration info. Legacy thread was 138746
 
Cheers, I'll give it a miss then.

I haven't had the car a week yet and am using the first month to build a snag list to go back to dealer with under OPC warranty.

I don't fancy having the prop disconnected etc.

Migration info. Legacy thread was 138752
 
I thought there were some places where you could run 4WD cars now?

Migration info. Legacy thread was 138820
 
Previous poster said:
Quote: Originally posted by So Poo on 04 May 2007
I thought there were some places where you could run 4WD cars now?

You can run Subarus, Mitsubishis etc on a 4wd RR it's that Porsches have a little more intelligence in their drivetrains to run successfully.

Migration info. Legacy thread was 138825
 
Previous poster said:
Quote: Originally posted by damianc4s on 04 May 2007

Previous poster said:
Quote: Originally posted by So Poo on 04 May 2007

I thought there were some places where you could run 4WD cars now?
You can run Subarus, Mitsubishis etc on a 4wd RR it's that Porsches have a little more intelligence in their drivetrains to run successfully.

DMC mentioned something about it a couple of weeks ago.

Migration info. Legacy thread was 138838
 
Porsche use an uneven split viscous coupling - 95% rear unless traction is lost, then up to 40% front as required: Unless the resistance from front and rear rollers is absolutely identical the electronics will assume the car is out of control and keep transferring drive between front and rear and could 'rock' the car out of the rollers I suspect?

Even if you turn PSM off (which you should anyway incidentally, as high powered cars will shift side-to-side slightly and could trigger PSM activity) this has no effect on the viscous coupling.

I may be wrong, but I believe 4WD rolling roads assume an 'open' centre diff/coupling and calculate bhp by a formula using the figure at the measured axle?


Migration info. Legacy thread was 138912
 
I was told not to take my 993TT on a RR by JZM. I a little hazzey why steve said it was a bad idea but something like engine can detonate and you wont know till long after

Migration info. Legacy thread was 138970
 
Previous poster said:
Quote: Originally posted by smtk on 05 May 2007
I was told not to take my 993TT on a RR by JZM. I a little hazzey why steve said it was a bad idea but something like engine can detonate and you wont know till long after

Not enough airflow on most dynos. WRC's at Silverstone has run many 993 Turbos although that's only with the massive fans Allan has put in place to replace the missing airflow.

Migration info. Legacy thread was 139003
 

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