RobC4sX51

In December I had the X51 factory upgrade kit installed on my 2013 C4S. The car had 23,500 miles on it. There are several other requirements per Porsche to do if you install this mod after 25,000 miles (such as new crankshaft rod bearings etc). The break in period was 310 miles below 4K rpm. I followed the procedure. I now have 24,100 miles on my car. The above pics are the only "visual" indications of the install, and these items can actually be purchased separately and installed (3rd radiator and the carbon fiber "engine" cover panel). As a refresher, the X51 includes new intake cams, new heads, and a new 6 +1 shiftable valve aluminum intake apparatus. This last item accounts for about 50% of the 30 hp increase. The DME is also upgraded through PIWIS.
Here are my impressions: the car is noticeably different in a good way below 3k rpm and above 3,500 rpm. The 3rd radiator makes the warm up time a bit longer but no temp change in normal driving. I haven't driven it "track hard" yet to see if there is any difference there. There is a deeper sound emitting from the exhaust and inside the car (not PSE). The performance change is most noticeable in how quickly the engine revs in normal and sport mode. I can't tell any difference in sport plus mode. The engine loves to rev is all I can say.
Now the bad news: Before this mod I did not pay much attention to threads or info regarding the "stumble/hesitation" issue well documented here on Rennlist but especially on 6Speed. I am well aware of it now. My modified X51 engine now has the dreaded "vario-cam" issue at about 3200 rpm in shifts from 1st to 2nd gear and again 2 to 3. This takes moderate throttle input. Low and high throttle input are not an issue. And I can't feel it beyond 3rd gear. Am I disappointed? Yes, am I sorry I did the mod? Not really. I can drive the car in a way that I avoid the rpm range and it doesn't do it every time, more like 1 in 10 times, more so under load like going up a hill. My dealer service tech is aware of it and drove the car with me. He feels bad but it is nothing he did. Last thing, careful what you wish for. But I still love this car, and it will be wonderful on the track in sport plus mode I'm sure. Thanks to STG and Lexvan for their support. That's all.

Hurricane

Congrats! Coming from a 991S to a 991S with the PowerKit myself, I would echo your observations. It definitely feels quicker to me, especially in the higher RPMs and the PSE note has a little more bark than the normal 3.8 flat six.

I don't have the "stumble" (didn't have it on my previous non-X51 991S, either) so it really seems hit or miss in a lot of ways. Or I am just not situationally aware enough to notice it.

Needsdecaf

Sorry to hear about the stumble. I know Money2536 had it on his power kit car...,wonder if that is the root of it?

RobC4sX51

The X51 is definitely not the root of the stumble. In fact the base model 3.4 seems more suspcetible to it. But no 9A1 engine other than the Turbo is immune to it. Some cars are more "seamless" at the vario-cam switch over from low (economy) to high (performance) at the 2800-3200 range point. Mine you can definitely feel "sometimes"!

Hurricane

Sorry about the stumble issue but hope you are enjoying the X51 anyways!

RobC4sX51

You Bet! Love it. The engine has come alive like nothing before. After the break in period I have put my foot into it a few times and am surprised at how fast the engine accelerates to redline. Only downside (besides the aforementioned stumble -which is very infrequent AND avoidable) is my MPG. I'm having so much fun w it that my fuel economy has decreased from about 17.5 average to about 15! Puts a big smile on my face! Thx.

Hurricane

Yeah I notice when I put it into Sport mode, I can almost watch my gas gauge needle go down hahaha! But so much fun to drive!

General Jack

Nice, thanks for the update.

PCA1983

My dealer told me that will happen without the exhaust upgrade, which includes headers and some sort of more open PSE. But are you saying you shift at high enough rpm that it drops to the 3250 flat spot rpm after the shift?
My interpretation is the X51 factory option with exhaust upgrade eliminates the flat spot. But I have not driven one, so can only mention what the dealer said.
It is common for aftermarket exhaust suppliers to claim torque is improved and the flat spot eliminated.

RobC4sX51

I have a SharkWerks side muffler delete (aka Race exhaust). My symptom is manifested from a stop or being very slow in 1st gear and then giving it enough gas to raise the rpm to just above 3k. As it shifts into 2nd gear and then again into 3rd I get a "jerky" stumble or hesitation. This only happens at that specific throttle input (& holding it steady) at about 3200 rpm, a little less if climbing a hill, and never when descending! And not if the car is moving in 2nd bear or highter already, and never in 4th gear or higher. And only about 1 in 10 attempts! I can't "make" it do it every time! Not sure why! But I can live with it now that I know what to avoid: medium throttle input from a stop or rolling stop! Hope this helps.

PCA1983

Those sound like low shift points, IMO. My typical shift in the 5500-6500 range after oil is hot, and sometimes higher. It's a lot more fun driving my 7M 991.1 C2S that way. I use mine for exhilarating blasts on nice days. We have a 2015 Lexus RX350 beater used for rainy days and nightime use.

vodkag

want to bring this old thread up as i am thinking about getting the X51 kit.

how much was the installation cost on it?

and parts?