I have a new 40th Anniv 911 which comes with with X51 performance kit. I've noticed that around 3200 RPM there is a bit of a stumble or cam shift. It is more noticable that I'd expect so am wondering if it is normal. Anyone else notice the same thing with the X51 package?

 

Had a similar ting on my GT3CS at 6000 rpm, turned out to be faulty hall sensors.

Ciao,

Johannes E.

 

Sounds like it's your Variocam+ doing what it is supposed to do.
Quite normal

 

Thats the variocam+, all of the engines do it.

 

Just for a reference, my previous car was a 2000 Boxster S and while I could feel it coming on cam in terms of a "rush", this is more like "slight jerk"; even at normal/casual street driving speeds. On the Boxster, I only noticed when getting on the throttle aggresively.

 

What are "hall" sensors?

 

hall sensor is an optical trigger for the ignition, I think they can also be magnetic? anyways you have a crank trigger if i am not mistaken???

 

As far as I know, the hall sensors measure the rpm of the camshafts. That is at least what my tech told me at the dealers.

Ciao,

Johannes E.

 

If you look at the X51 cams, the difference between the low speed and the high speed lobs is significant. Enjoy the stumble and what comes right after it.

 

Thanks for the info - I felt something at that same RPM in my newly purchased 40th anniversary edition - it seems to happen in 2nd gear at 3.2k rpms.

 

Same question I asked a looong time about my 2002 C4S; just the variocam plus kicking in.

I believe before 2002 was just variocam (not plus).
Enjoy the variocam plus kick, and enjoy the fuel economy when it is not engaged.

If it is not a kick or "rush" but a stumble or hesitation, then you have a problem.

 

The x51 has a more defined bump/stumble than a non-x51 car... and it certainly pulls harder as it goes faster and faster!

 

My X51 has never had any PRONOUNCED stumble at 3200...but I sure do love how it races for the redline once I hit 6000!

 

Holy 2004 Batman

 

the surge at 3200 rpm is variocam + like everyone mentioned. The surge is more noticeable with hacked mufflers. That is one of the reasons I went back to the stock exhaust. I also felt more low-end power with the stock cans. I had Daren Fister’s Mod ll, I loved the sound and think the mod was worth the money but I liked the smoothness and low-end power more.