John 996 TT Cab

I can press the PSE button at any RPM and hear a difference in sound. Slight at low speed but noticeable. My X51 is factory install. I don't use Sport or Sport + when the car is not at oil temp of at least 165'F. My understanding is Sport and Sport+ open up more cooling ability. Getting to a decent temperature of the oil in the 991 with X51 is about the same time as it takes my 2012 650 to get the oil up to temperature. Takes about 6 - 8 miles or so.

9114s

At the dealer now, one solenoid did not work properly. PSE now works as the C2S 50th anniversary with X51 and PSE from factory I just tried at the dealership. it now also recognizes the PSE dash button and works with auto coding, no need to program it manually..

9114s

http://www.porscheengineering.com/pe...tomermagazine/ engineering magazine ISSUE 2/2012

Here you will find more info about X51 for the 991 Carrera S/4S. It is amazing improvement to my car with no downside. Yes I have a lighter wallet but it is worth it.

I understand why it is included into the USA 50th anniversary limited series. Even at low RPM you can feel the difference, the engine is more responsive and when you touch 5000 rpm the car explodes and jump to 7800 rpm, the PDK does his magic and the rush continues...
As you can tell I love it.
Porsche did a magnificent job with the PSE this time.

A new GT3 (under dry condition) or a Turbo will be needed to see more than..

Money2536

Thank you for this!

9114s

The front vacuum cleaner to keep it cool.

Bacura

My butt is way less sensitive than yours. I can barely notice any difference from my 997.2S to the 991 X-51. I'm glad I have it but the difference is slightly more than tiny. If I am reading those graphs correctly there is almost no difference till you hit 6500 rpm. In normal driving there is basically no difference at all.

9114s

Sorry I have no personal data point 997 vs 991... I guess "normal driving" at 70mph both car run at 70mph yes.
These are just my honest feedback on my car 991 C4S PDK without and with the kit installed, 2 other drivers of my car have the same sensitive butt....

chuckbdc

In my one back to back test (my C2S coupe without X-51, and a friends C4S Cab with X-51) I felt an obvious difference in his engine's top end rush to the red line (eg above about 5k to 7.5k rpm). He commented that mine was faster than his, and it may be, given the weight difference, but I sure would like the extra zing when I asked for it.

The more precise induction system, cams and valves and ported and polished heads are all well proven performance improving tricks. I recall reading somewhere that the advantage of the X-51 grows as the engine is run in. I don't know why that should be true, but I have no reason to doubt the factory.

General Jack

This is why I like the x51, its not inflated hp claims from dyno tricks or smoke and mirrors like some aftermarket mods. The x51 is true mechanical upgrades from internal engine upgrades that increase airflow. As more info comes in, I'm hoping to see that it provides significantly more than the (typical) conservative factory claims of 0.1 to 0-60 gain.

Bacura

Since the torque is basically unchanged I am willing to bet the 0-60 time won't be that much more than .1 faster. Quarter mile might show more of a difference. It's standard in the NA 911/50 and even if it wasn't I would have ordered it. I like the engineering but I'm afraid the performance is only better in the high rev range when really pushed. To me it's torque that makes you feel a difference in the butt.

Suzy991

Absolutely true....

Suzy (via iOS app)

General Jack

I agree that almost certainly a greater quantitative difference would show up in the quarter mile or road course lap.

Money2536

I would really love to see an X-51 vs. non from a roll. It's going to take me about a year to make that happen assuming 6,000 miles or so is required to reach max power output.

chuckbdc

Based on my one drive in an X-51, you are going to get your money's worth of smiles way sooner. With your build you may have some in the GT3 crowd jealous.

Drifting

Sounds like the current X51 option is a nice one and more worthwhile for the 991 than the 997 X51 variants.

I don't think you'll be making a GT3 jealous however.

-------0-60 instrumented times as tested by Car and Driver------

991 GT3 3.0 seconds flat
991 C4S 4.0 seconds flat.

Highly doubt the X51 will add subtract more than .1 second from that, so no you won't be challenging any GT3s on a road or track.

GT3 is a much better performance car than a 991 with X51, hand down. It's also a fabulous deal at $130,000. If you order a 991 with X51, PDK, and basic options that are standard on a GT3, you're already at $125,000. And with a GT3 you get another 45HP, much quicker shifting, better brakes, better steering feedback, better handling, RWS, better chassis and more durable components(built for stress of racing), than a regular 991 with X51.

The only reasons to order a 991 with X51 are if 1-you must have AWD, 2-want a convertible, 3-hate to drive anything but a manual, or 4-kids will ride in back seats very frequently.

Otherwise, the 991 GT3 is the way to go.