Hi, I'm looking into getting a 991 TTS but have heard rumors of a few issues with the DME and slick or race tires. From what I have heard when using slick tires on a 991 TTS, the rear wheel steering accelerometer sees too much G forces being produced, the DME is programmed to think something is wrong and sends the car into limp mode.

I am sure if they did the above, they would also place in one for acceleration and braking, and that this would cause a similar limp mode with some of the highly modded cars..

Also I was informed the 991 changed the DME from an open Bosch to an encrypted Siemens, making it harder to makes changes to the issue listed above. It sure would be nice if we could just disable the map for this or increase the G forces by 50%.

Any of the mod companies or if anyone has experienced something similar to this, please chime in!

 

Where did you hear these rumors and how confident are you that they're substantiated? The reason I ask is because I actually CANNOT FIND any race or track tires for my 991 Turbo S with the 20" rim, so I was going to post here asking if anyone had found a 19" rim that'd still clear those big 16.5" PCCM brakes (and, if so, what sized tire did they match with the 19" wheels to keep the same rolling radius, etc, so as not to screw up the car's finely tuned systems).

 

I think this is something that will take some time to reveal itself. On the 997.2, I know there was a bit of an adaptation period when changing to very sticky tires, but it did sort itself (at least on tuned vehicles). On previous models, the PASM could be thrown off by even a slight change in tire height, something worth noting when switching to slicks.

 

It came form a pretty reliable source. I do not think an adaptation period would do much as this is a different DME and the RWS max G forces are set, supposedly for warranty reasons and to tell the system something is wrong...

I was hoping to go to 18" wheels on it with slicks, as I cannot find 19's in any size that makes sense and no 20" slicks at all.

 

My service center has not been able to get any recommendations or settings adjustments for running track tires on my 991TTS.

Just as a follow up, my dealer also passed on to me that Porsche isn't recommending track tires for the 991 GT3, either! So, apparently you're limited to an R-compound street tire like the MPSC2 (N0) for both the GT3 and the TTS--which is really too bad, because the track I use most will literally destroy a set of those $2400 20" MPSC2's in 1-2 track days. :-/

...and that's why I'm now looking for a tuned 997 that I can put 18" track tires on so my favorite sport's consumables cost remains within wifely tolerances!

 

The 2015 users manual for my TTS is specific about slicks. If used, the engine warranty is voided because transverse acceleration would cause oil starvation in the engine. Same warning for the GT3, which is fitted with Michelin PSC II's I believe. For track, I would use the same tires as on the GT3. Porsche engineers are very prudent and obviously have designed systems to protect the engine, although the manual does not include a description of the limp mode mentioned above.

 

I am wondering if this has something to do with why I couldn't launch my car at the dragstrip on winter tires. It would spin for a split second and then the RPM's would drop to 2k. The GM at my dealer thought it might be the ECU going into failsafe mode and just canceling the LC on me because of the grip of the winter compound. Interesting. I did not think it could be the case, but who knows.

 

I don't agree with this information as i have completed more than 200 laps on our national F1 circuit.

I have seen 1.7g at cornering with Pirelli Trofeo R tires on my 991 TTS at todays trackday without any problem.

 

Now we're talking! Have you by any chance talked to a dealer to verify that these, as a "streetable track/competition tire" (which is how the Michelin PSC2's are billed, I believe), will not void the warranty?

Of course, being so soft and sticky--which admittedly is what we're looking for--the word in the forums is that they're a 3-4 track day tire, which in a 20" is $2400/weekend of driving. Ouch!

So now you can really make my day if you are running these on a 19" rim, on a car with PCCBs, which would save us several hundred bucks per weekend! If so, please post the rim sizes and offsets and tire sizes you went with if other than stock, so I can stop shopping for an older 911 turbo for the track, and just focus on running my new 991TTS into the ground... :-/

...of course, that would also mean abandoning my newly created dream of going overboard and finding a 800-900+ hp 997.1 for my "track car" to make those track days *really* hair-raisingly fun! ;-)

 

Perhaps I missed something and if so my apologies, but what information do you disagree with? That the Owner's Manual says that the use of slicks will void the warranty on a 991 TTS?

 

I think he was disagreeing with my assertion that the car's performance was tire limited, because you had to run streetable tires, and the only tires I'd been able to find for the car were the Pirelli P Zeros (which suck for track use) and the (semi)R-compound Michelin PSC2(N0), which are better, and a little more durable, but not hugely sticky and still get eaten pretty quickly by some tracks.

The thing that would be harder to argue is that the requirement to run 20" streetable tires, which run $2300+ per set and which are destroyed by a 2-3 days on the track (at least for some tracks, especially those with a few long sweepers that really draw out this car's tendency to push around such turns), make this a more expensive car to track then many others if you're trying to run with the big dogs.

That's why I was hoping to hear from someone who'd found a 19" rim with a tire that wouldn't void the warranty, but would be more competitive around the turns with those running Hoosiers or Hankook slicks, or at least the Toyo terrors out there. :-)

 

EnzoM posted this link: http://www.germancarforum.com/thread...turbo-s.51924/

GT3 had Michelin PSC2's and TT/TTS had Dunlop Sport Maxx Race tires.
Fascinating lateral G force readings in the post with the TTS pulling more than the others. Of course, it could have been different drivers so circuit times might vary among the three, but the comparison tells me that they are close enough to be competitive on a similar profile circuit. Wonder why the TT/TTS had Dunlop tires and not the MPSC2's. Not sure where to get Pirelli Trofeo R set in same size as stock or other brands of streetable/track tires.

 

Let me repeat that I'm really thrilled to see this report. Have you done any modification or tuning to the suspension or drive train? And would you please share what alignment / camber specs you're using, if anything other than OEM defaults? Thanks!

 

Hello,

Suspension and drivetrain is completely stock.

I align the tires in factory tolerances.

The car is animal on track !!!

 

Maybe they are talking about full slick tires...

I haven't seen any downside of using semi-slick tires. (Trofeo R)