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If it's not clutch (that's literally the sympthoms of an clutch that is not good), I remember someone on 6speedonline finding the reason and culprid for this, from memory it was some kind of sensor on the wheels, very weird thing to be related, I think that there was a new part that fixed this.
Yes I knoe that makes very little sense, but again it's from memory so I might be mixing things up, but appatently it was the solution for a couple of people and the thread is around somewhere.
try doing this on 6speed despite all there are much more turbo cars owners ans specialists there than here.
I think it's normal. Mine does it. I can manage to avoid it when focused.
Think it's a driver issue, if you are very fast shifting and lift from the gas pedal too slowly it will "over rev". It's easier to miss in the lower gears, mostly 2nd to 3rd.
Good thing is that our engine doesn't mind. Over revs on the turbo engine is not like over revs in the gt3/cup engines.
I would not worry to much about it. Actually I don't and I worry way to much about my cars.
Pretty sure it’s not a driver issue. The only way I’ve been able to prevent it is by shifting so slowly the revs drop to the point I have to rev match into the next gear. Just can’t drive it spiritedly without the revs jumping. Doesn’t happen in any other Porsche I’ve driven or any other manual car I own for that matter.
Still in contact with some local dealers who are saying there is no related TSB for the GT2. Looking into it on Turbo models.
A well-known performance shop near me has seen this happen but only on flashed cars. Mine’s totally stock from what I can tell.
Take a look at the data in the pic below, see how when the throttle pedal is at zero during a gear change the ECU keeps the throttle open somewhat (Actual throttle column). If you look to the left you can see how the revs rise during the gearchange up to 7839rpm in this instance.
So I reckon it is this open throttle which is causing the revs to jump as the load is taken off the engine during the gear change,. I don't think the regular turbo also does this but if it doesn't and data logging also shows a fully closed Actual throttle then this would prove my theory
BTW it has the same pattern at every gearchange on the logs the clip below is not a one off it is its modus op
I had this issue with a supercharged lotus exige that I owned about 5 years ago, although the blip was not as drastic as shown in the video above. The shop who designed the kit suggested it was left over air in the intercooler and boost piping (after the TB had closed). I would assume the GT2 has twin blow off valves to prevent this? Could it be a fault with the BOVs or their plumbing?
I sent my GT2 to Jimmy Repasi at Porsche Fairfield. Jimmy is the man when it comes to CGT's and Porsche GT cars.
He drove my car and said I definitely was not nuts (at least with respect to the engine revving up between shifts). Jimmy tracked the problem down to an intermittent leak in an elbow vacuum line leading to the recirculating valve for maintaining boost pressure between shifts. My car recently had the coil packs replaced and if not careful during that procedure you can put too much pressure on that vacuum line, which is now 10 years old and a little brittle. The elbow vacuum line is Porsche part number 997.110.666.71
Boost pressure recirculating valve Elbow vacuum line Testing for vacuum leaks
Here is a video of the offending vacuum line leaking
I sent my GT2 to Jimmy Repasi at Porsche Fairfield. Jimmy is the man when it comes to CGT's and Porsche GT cars.
He drove my car and said I definitely was not nuts (at least with respect to the engine revving up between shifts). Jimmy tracked the problem down to an intermittent leak in an elbow vacuum line leading to the recirculating valve for maintaining boost pressure between shifts. My car recently had the coil packs replaced and if not careful during that procedure you can put too much pressure on that vacuum line, which is now 10 years old and a little brittle. The elbow vacuum line is Porsche part number 997.110.666.71
I can't see that what you describe will have got rid of this, my thinking is
The 997 turbo has the same set up so why do they not do this ?
My GT2 did this when brand new and 100% stock so no leakages or knackered tubing.
My current engine in the vid above is highly modified and doesn't have this piping, it runs K24 turbos using dual powered wastegates off an N75 valve via the VTG signal.
I think it's much more likely to be something intrinsic to the GT2 Motronic programming, the GT2 ECU is different to the 997 turbo as per my post above.
I sent my GT2 to Jimmy Repasi at Porsche Fairfield. Jimmy is the man when it comes to CGT's and Porsche GT cars.
He drove my car and said I definitely was not nuts (at least with respect to the engine revving up between shifts). Jimmy tracked the problem down to an intermittent leak in an elbow vacuum line leading to the recirculating valve for maintaining boost pressure between shifts. My car recently had the coil packs replaced and if not careful during that procedure you can put too much pressure on that vacuum line, which is now 10 years old and a little brittle. The elbow vacuum line is Porsche part number 997.110.666.71
Boost pressure recirculating valve Elbow vacuum line Testing for vacuum leaks
Very cool I hope this solved it. Still interesting that the engine continues to receive both fuel and spark after the throttle is lifted since that's the only way it would continue to get power to over rev.
Currently dealing with this issues, one shop that claimed they were “specialists “ couldn’t fix it for two weeks
at a new shop and they think it might be the giac tune however this threads leads me to believe its most likely not tune related as it happens on stock cars.
12-20-2018, 06:54 AM
