I am posting some content of messages I have sent to a friend as I am seeking advice on this and I am hoping others may chime in on this and let me know if they have this experience. If you do experience this with your car please let me know.

I'm having what I think is a real issue and I need some opinion/advice I noticed the other day that if I am at a dead stop and I just mash the gas (not launch control) the car just sits there for a second or so then launches hard. It almost feels like massive turbo lag like you'd get in an 1980s turbo z :-) very weird. I am always in sport+ but I tried in normal mode too. Did it several times tonight. I know it didn't always do this as a few days ago I took of from a light like a rocket. So fast it felt like a launch. Very troubling.

The car is in fact very much warmed up. I am at a dead stop, mash the pedal and the car sits there for a good half second and the engine roars up to about 2k RPMS or so then it goes. It is a delay as if the tires were spinning and then the car got traction and took off except that the tires are definitely not spinning. Again, it's if I absolutely mash it to the floor from a stop. I wonder if it could be the car breaking itself so because tires are wanting to spin? That makes no sense to me though since it will do LC just fine. I only did a launch the other day because I felt it do this and I wanted to see if it would actually launch properly having felt it. Same thing tonight. 2 launches total.

 

I tried to respond to your PM on the other board but your inbox is full LOL... I think it might be a pdk slippage; get it checked.

 

I replied on the other board that I have the same issue and believe this is normal. If this were a regular manual transmission and you dumped the clutch from a very low rpm it would either stall or bog down until the revs climbed. The PDK is doing this except it doesn't allow a stall. The low rpm turbo nature of the engine may enhance this effect, as does the all wheel drive.

You could try an automatic transmission style brake torque launch where you hold revs while holding the car with the brake until the slack in the fluid is taken up. I don't know if this is very good for the PDK although this is the same as a Sport Plus launch control start but where you decide the initial rpm.

 

I agree with Vic. That doesn't sound normal at all and sounds like the clutch plates are slipping. Perhaps a software update or re-set is needed for the TCU? As you even begin to mash on the accelerator the clutches should engage, (when not in LC mode), and the car should begin to move off until the turbos kick in and away you go. There is no way a 1/2 second lag is normal with a modern car that just doesn't move during that 1/2 second.
Bish

 

Yes. i got it and thanks! I think you are 100% correct. I think you have described it much better than I did.


Thanks Bish. i think Cartester is correct. It is not that the car does not move. It just is a very slow start then the turbos kick and whoosshhh.... I am tkiang th ecar in for an unrelated service tomm. I will have it double checked then.

 

Could it simply be the computer waiting for the turbos to spool up? I mean they are turbos and they must spool still regardless of how well they're engineered, especially from a dead stop. I had this same thing happen on my brand new '11 TTS which was literally 30-minutes old. I pulled out on a busy street and cut it too close, had to floor it only to have the same thing happen. I almost got hit but thankfully they finally kicked in and got me through it. That second seemed like an eternity, scared the crap out of me.

 

What you're experiencing is due to the fact that when you're completely stopped, the PDK clutches are disengaged and the car is essentially in a "neutral" mode (although not necessarily a neurtral gear). Ever notice how the car slight lurches forward if you just take your foot off the brake? That's the transmission going into gear, if you will.

If you just mash the gas from a dead stop, that split second delay is intentionally there to make the car feel smoother as it initially starts rolling. If you were in sport or sport plus, it should be slightly less noticeable.

Next time you drive the car try this. Don't do a full launch control, but as your stopped just lightly press the gas while you're still on the brake. Just enough to rev the engine to maybe 1500 rpm's or so. Then let go and mash the gas...that "lag" shouldn't be there.

 

So Tom isn't that indeed considered to be some "spool up" lag time too? I mean essentially you're eliminating this when you raise the RPM's as you stated. Its not all just PDK in other words...

 

No not really. "lag" or "spool up" would refer to the delay you experience as the turbos build boost pressure. However, keep in mind that even when out of boost, the car still moves under the power of the engine. You're not actually making any boost until the engine is under a much heavier load. 1500 rpm's will not make any boost, but it will be enough to keep the gear engaged.

The delay you're feeling is something that's programmed into the car. Imagine you had an old car with an automatic transmission, and you put the car from "N" to "D" while revving the engine to about 2k rpm's. You'd feel a slight clunk as the gear engages. That delay you feel is essentially the PDK programming preventing you from feeling that "clunk".

 

I think you're right. I only have a 997.1 turbo tip, but I posted about this several times a few years ago. That basically, unless you're brake boosting with a tip or using launch control with a PDK car, these cars are slightly "anemic" for the first 1/2 second after you mash the gas. They definitely move forward and start to go, but they don't rip off the line they way you'd hope. After that half second though, watch out! Search this forum as there have been a number of threads about this. Seems that even with PDK and the VTG of our turbo's, there's always a bit of lag unless of course you brake boost or use LC.

 

Today I finally had the opportunity to test this and get back to you (my new Turbo S coupe has 195 miles). This morning I flubbed the test because I didn't mash the pedal all the way to the floor - maybe 3/4 or 7/8. In this case the car just took off no delay.

On my way home this evening at the same light I had plenty of time to prep and no other cars were around. Kept my foot on brake, light turned green. Moved my foot over and pushed the gas pedal down to the floor. The car immediately jumped forward - no delay - reached 50mph in what seemed like two seconds or so. I haven't launched the car yet with launch control, but even this pseudo launch was crazy - almost scary. I've previously launched my last car several times, but there was something more violent/aggressive with the Turbo S acceleration.

My experience makes me think you have an issue with your car - this is not a built in safety feature. Hope Porsche fixes it for you.

 

Thanks for the extremely informative response. Great to be reassured by someone who knows.

This confirms my initial suspicions about the behavior and the comments by a few members here. What had me a little concerned was that the delay seemed a bit inconsistent, being seemingly longer the first day. It likely was no different and more a case of me thinking that it was.

Thanks again. Greatly appreciated.

Mike

 

Awesome now that you got it from a reliable source let the placebo effect take place and the delay will be gone

 

Ha Vic! That was until I went to Hennessy today and a very good tech I know drove it and noticed it was also doing it a bit from a roll and said it shouldn't. Thought it was clutch adaptations or something. Is running some diagnostics and comparing measurements against another PDK TTS that just rolled off the truck.

 

Any reason why this isn't the all-too-common electronic throttle lag? It's a safety/legal thing. My Ram 2500 CTD has it. My wife's 535xi has it. It is intentional. The car is saying "do you really mean it?" The more unusual your input (sudden full throttle after putting around for 20 minutes) the more the car doubts your intentions.