Tier1Terrier

I’m very interested in the final outcome of this.

F355bob

i will post what the fix is

paddlefoot64

Isn’t common to have shudder around 3000 rpm, Variocam associated?

stout

My 2018 991.2 Carrera has an occasional stumble in "steady state" cruising or light throttle acceleration—though it's so slight I find myself questioning whether it's perception or reality.

First time I felt something similar was in a 996 R Turbo I was driving with Alois Ruf riding shotgun years ago. I mentioned it. He nodded, having felt it too, and said "normal, and not worrisome." I've felt it in plenty of cars since then. I'd be more worried if a Check Engine light came on or I saw other issues—or heard about fault codes after a service.

F355bob

This is more than a stumble that you might think is there or not. It is very noticeable. It is hard to describe. All I can say the car shutters down to the suspension for a second. You feel it all the way to the tires

enzotcat

Does your TC light flash on at all when this happens? For me - new GTS turbos + APR GTS Stage 3 tune - I can get the TC light to come on easily under hard acceleration in 2nd gear. Feels very much like a shudder aka wheel hop. When it happens, do the revs drop at all?

rnl

that was my thought. porsche does not include replacement of these items (there are two) as an ordinary maintenance feature. when they go acceleration is pokey.

spdracerut

This is not uncommon on turbo cars. It's that tipping point of the BOV being open or closed. At highway cruising speed at steady state, there's enough exhaust energy for the turbos to make positive pressure in front of the throttle plate and the intake manifold pressure still has some vacuum as the throttle plate is mostly closed, so the BOVs are right at that point where they are between open/close. So if the BOV flutters between open/close, it'll create that stumble.

F355bob

My turbo Macan does not feel like it has a flutter or is so small you can't feel it. My 911 flutter was not there before the tune. This is a 1 sec severe flutter. Possible tune has nothing to do with it and will know when I put stock fike back on.

polobai

It’s possible that it can be wheel hop but I wouldn’t expect it at those speeds rolling. Taking off from a stop, or 1st to 2nd gear change, sure but not at 70-80 mph. Can you post a video of it happening?

Norge911

The torque curve on the FVD tune is very steep and max torque is early. Full throttle at this rpm can overwhelm the peak torque allowed by the computers.
Why it is important understand how each of these companies make their tune.

Try two things;
1. at same rpm and speed, squeeze throttle at 1/2 to 1/3 speed of what you did before and see if this changes behavior
2. Downshift to lower gear, same speed but now rpm should be 5-5500 rpm, floor throttle like before.

if either these two things changes the hop, then the problem is too much torque and the launch point. Too change this, either change your driving habit or change the tune to Softronic, APR or VF engineering. Their torque curves are tuned differently and torque curve is not as steep.

F355bob

I'm thinking it is a misfire. I did give it less throttle and it did it once. It is so inconsistant and hard to replicate. 90% of time it does not do it. Removed tune this morn and will drive this pm to see if I can get it to do it. Large snow storm on its way so testing might be limited for a few days. The FVD
really is great. It is a whole different car with it and problem might be unrelated to tune

F355bob

Contacted FVD and they sent a new file to download. It has seemed to fix it so was not an engine or PDK problem but just a software glitch st thst rpm and load .
Car really runs great with this tune and hwy gas milage increased by 10%. After putting stock tune back in to experiment, I could never go back to a stock tune.

Tier1Terrier

@F355bob Glad to hear this outcome assuming that the problem you were experiencing is no longer there and that it is indeed fixed. Based on this, do you now believe it was the tune that was causing the issue? Have you been able to replicate the problem since the tune was re-programmed? How was FVD to deal with? Did they give you an explanation as to why there was this glitch? Did they give you any additional details on this glitch?

The reason I ask all this is because the FVD tune is currently at the top of my list. I just want to know what I'm getting into if I decide to pull the trigger on this tune. I have a 991.2 C2S.

F355bob

service has been very good and I can't replicate the problem with the new tune file. Cars runs very strong for a "mild" tune .I am running 93 octane. They said it was a driver interpretation map based on rpm and load and they have seen it before.
New file sent overnight and install was 10 minutes.
The car is much faster, smoother, and even PDK shifts smoother in Sport+ without the jerking in the stock tune.