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-   -   991S PDK throttle hesitation from start (https://rennlist.com/forums/991/764160-991s-pdk-throttle-hesitation-from-start.html)

CarManDSL 07-01-2013 02:35 PM

991S PDK throttle hesitation from start
 
Have a May'12 build 991S, PDK, S-Chrono, S-PASM, 11k km. Now that summer weather has arrived, and driving-like-I-stole-it whenever possible, a throttle hesitation issue has come up.

On fast acceleration from a stop, the initial few hundred RPM's from idle, there is a hesitation. This is in manual or auto, Normal, Sport or Sport Plus.

Smooth application of throttle from start, this does not happen, but only when I hit the throttle as to get into traffic quickly. I haven't tried hitting the kick down button in this way as generally getting into traffic entails a 90 degree turn and I'd initiate a spin.

I've tried a left foot on brake pedal and raising throttle to 1,500 rpm type launch but that is not practical.

What is your experience?

Jay-S 07-01-2013 03:00 PM

Exact same for me (991-4S PDK). There is maybe a 1 second (?) lag when the accelerator is depressed aggressively from a stop when it feels like nothing is happening.

I just recently figured out that smooth application doesn't give you that lag but haven't played with it enough to figure out if I like that approach better.

Cogito_Ergo_Zoom 07-01-2013 05:17 PM

https://rennlist.com/forums/showthre...errerid=119246

Jay-S 07-01-2013 06:32 PM


Originally Posted by Cogito_Ergo_Zoom (Post 10579543)

I saw that thread at the time but not the end of it where it talks about the lag from a start so thanks for the link. FWIW I've never noticed an issue in 2nd gear or in the 2,500-3,000 rpm range. Interesting.

CarManDSL 07-01-2013 10:38 PM

Made this video today to try to demonstrate the throttle response or acceleration hesitation issue.



Carcam 07-01-2013 10:58 PM

I have the same car and have not noticed it... although compared to my Cayenne diesel with all the low end torque, the 991S seems slow at low rpm. I chalked it up to being a low torque, high rpm engine. Maybe a software tweak can fix it for you. I couldn't really see it in your video, I guess because I can't see the tach or your accelerator pedal.

jlanka 07-02-2013 12:20 AM

Nice troubleshooting video.

Now, have you taken the service manager at the dealership for a ride to demo it to him?

CarManDSL 07-02-2013 03:26 AM


Originally Posted by Carcam (Post 10580403)
I have the same car and have not noticed it... although compared to my Cayenne diesel with all the low end torque, the 991S seems slow at low rpm. I chalked it up to being a low torque, high rpm engine. Maybe a software tweak can fix it for you. I couldn't really see it in your video, I guess because I can't see the tach or your accelerator pedal.

I do notice the relatively low torque of the 991S before about 2,500 rpm at which point it comes alive. This is much before that at 900 rpm. I was concerned as well that the acceleration hesitation would be hard to see on the video. I'll try your suggestion - video of the tach and pedal.



Originally Posted by jlanka (Post 10580544)
Nice troubleshooting video.

Now, have you taken the service manager at the dealership for a ride to demo it to him?

Have an appointment July 18.

Jay-S 07-02-2013 08:06 AM


Originally Posted by CarManDSL (Post 10580770)
Have an appointment July 18.

Let us know what they say. I chalked it up to PDK feathering the clutch to avoid excessive wear.

Detroit Shooter 07-02-2013 08:38 AM

It is an automatic manual. Would you expect that feeling if you were releasing the clutch?

WCE 07-02-2013 10:21 AM

I know most here love their PDK 991's but I highly recommend a test drive in a 6 speed automatic corvette for a reminder of what a sports car that jumps off the line from idle feels like!

Jay-S 07-02-2013 10:31 AM


Originally Posted by Detroit Shooter (Post 10580918)
It is an automatic manual. Would you expect that feeling if you were releasing the clutch?

Good point. Definitely would not expect it...but beats me how a computer does it ;)

extanker 07-02-2013 11:08 AM


Originally Posted by WCE (Post 10581081)
I know most here love their PDK 991's but I highly recommend a test drive in a 6 speed automatic corvette for a reminder of what a sports car that jumps off the line from idle feels like!

you nailed it right.many po owners found that out the hard way when they pulled up to a vette at a traffic light:bowdown::bigbye:

veilsideLGD 07-02-2013 03:05 PM

I had the update performed last Friday and have noticed the same thing. Immediately upon acceleration, there is a slight hesitation before the vehicle actually gets going. I've noticed this in all modes.

jlanka 07-02-2013 03:46 PM


Originally Posted by extanker (Post 10581190)
you nailed it right.many po owners found that out the hard way when they pulled up to a vette at a traffic light:bowdown::bigbye:

I think 911 owners are well aware their car is NOT a drag racer (read American Muscle) and more of an overall package (handling in addition). Don Garlits I'm not looking to be... Emerson Fittipaldi maybe...


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