Or maybe I should say, "a" case for the power kit. As I look at the specs for the brand new 991 GT3, my thoughts that the X51 option is the GT3 lite version, especially if carefully optioned, is confirmed.

Many on this forum have debated the merits of the X51 option. Comparing the two models, the GT3 develops 475 hp at a whopping 8250rpms, while the X51 develops 430 at 7500. By contrast, the GT3 pushes out one less pound foot of torque at 6250 rpms. Both engines are peaky, but the X51 reaches its peak torque at 5800 rpms.

For both engines to be fully enjoyed they need to be reved to the limit. Obviously for normal street driving, neither one of these machines is very practical given the power curves. After spending 6 hours behind the wheel of a 991S whose engine was fully broken in at 11,000 miles, this car truly has a dual personality, both of which I love!! I drove the car in anger. The GT3 is more of a single purpose car, that needs to be taken to the track to fully enjoy.

Finally, I find it interesting that there is really no information on Porsche's website regarding the X51, just a general announcement of the option, price, specs and a claim that it reduces 0-62 mph by 1/10th of a second. In other words, no 1/4 mile times, 0-100 times etc.. Is it possible that the X51 option is just a wee bit quicker or that the 0-60 mph claim of 3.3 for the GT3 is a bit optimistic given the spread of 30 hp from the S to the S w/X51 and a 45hp spread between the S X51 and the GT3? A 30 hp bump over the standard S produces a 1/10 of one second increase, while a 45 hp bump from the X51 to the GT3 produces a 1/2 second difference. Does the different gearing and weight reduction (??) account for the difference?? - just food for thought.

 

The revised close ratio, non overdrive PDK aids acceleration, and the additional torque don't hurt. Keep in mind that the incremental HP really starts to make itself obvious after the quarter mile. The GT3 according to the marketing material is going substantially faster and likely picking up speed much faster.

 

I like this thread. I don't feel so dumb now. Just don't ask my wife's opinion.

Regarding the X51 to the base 'S' model, there is a difference from 400hp to 430hp. It is not a HUGE difference, but it is there. It is a less than 10% change in the total output, making it subtle. I really haven't had the opportunity to find the differences except from experience on the track. I mentioned this before on another thread of mine, but will repeat it here. On the track at Roebling, with a clear road ahead of me, I was hitting 143mph on the front stretch before braking. With the upgrade, on a busier track, having to wait for the passing signals and cars ahead of me, resulting in less impetus coming out of the big curve and slower speeds, I was still hitting 135ish before braking. So, with less road to accelerate on due to traffic, and a slower starting speed, I was still almost able to achieve my highs from before with the base 991S.

I do not have much more to input beyond that. I would agree that it would be akin to a GT3 lite, and a bit cheaper too. I have not seen any numbers for the GT3 output yet either.

 

I went for the X51 rather than waiting for GT3 as getting a cabriolet was paramount. Still waiting for the X51 though but it should be here end of next week at 6.5 months from ordering.

John in Vancouver

 

I agree that the additional 45 in horse power will make itself known once you get past 100 mph and especially past 120 mph, but it still doesn't fully explain the difference. The fact that the GT3 has an actual 7th gear will help get you to the higher attained speed and increased acceleration in 7th gear, but it doesn't explain the huge difference in 0-60. By the way, the S develops 1 more lb/tq.

 

I don't know the ratios but: if they are all closer, and the PDK is more efficient and the engine revs another thousand RPMs and the car has 75 more HP- that would seem more than enough to explain it. Most of getting to 60 is overcoming starting from 0. I have not seen a quarter mile time for the new GT3 but if it is a second faster that a 991 S that is a LOT of car lengths at around 125 MPH!

 

Remember, we're comparing the Carrera S X51 w/430 vs. the GT3 w/475 so the net difference is 45 not 75 hp. Perhaps the dunlops are a lot stickier.

 

Lots of reasons. Better tires on the GT3. The GT3 is slightly lighter. Better gearing, etc. The better suspension and better aero wont' really affect 0-60 times. Of course, no one buys a GT3 for 0-60 times. It was made for the track, and not a straight one.

I've driven the 991 C2S both with and without the X51 kit. Honestly, I could not tell the difference. Maybe it's faster as your wallet is so much lighter?

 

All I know is, the X51 power kit is the only way to even approach the normally-asperated level of a GT3 in a cabriolet and a manual. A manual cabriolet X51 991S would be a special car. It already is a special car, hehe..anyway. Oh, I have X51 envy, but I already cannot take the car to it's maximum performance where I drive. I need to take a trip to some wide open space in Wyoming soon...

 

Does anyone know if you can change the gear ratios like I did in my Mustang. Putting in a 4:10 gear made a big difference in low end at the cost of a top speed I will never see. Given how much more complex my 991S is, I doubt that there are similar options (and certainly not under warrentee). Is this even an option?

I will not get a GT3 because it is all race car, all the time. (a great one to be sure). I love the jeckel and hyde nature of my 991S. At my age and other factors, and the roads here in NJ, speed is not an option most times and comfort is a growing factor. I would consider a turbo. But the Mrs. will likely let me do only that - consider it.

What other options are there for us torque junkys?

 

Wait for the 991.2. It'll be standard.

 

The ducktail has to be good for at least 2 tenths on 0 - 60. At least it will look that way.

 

With a little more research I found out that the GT3 actually weighs 33 lbs. more than the 991 S. ....still looking for gear ratios and attained speed in each gear.

 

I highly doubt it. The parts are too $$$.
You will see a bump in HP for the 991.2 for sure.

I think the X51 now that the GT3 pricing is out, is not worth it at all IMO. The GT3's motor is heavily revised and if I added the X51 to my order it would have easily approached GT3 prices.

 

Excellent point! ha! Actually Porsche put out the 0-62 time and in the absence of additional info we can, I suppose, extrapolate the 0-100 and 1/4 mile.