AltitudeRacing

Howdy folks, i have a question. I have a new to me 997.2 carrera s and at full rpm shifting no combination of footwork is able to get past the rev hang. The revs dont drop when i let the clutch off immediately, they hold for a second until the next gear is in unless i shift super slow. This is driving me nuts and i hate the way it feels. Does anyone know if the cobb accessport can tune this out or if there are any other options?

anewman

If its a manual transmission, are you sure the clutch isn’t slipping?

Wayne Smith

Correct me if I'm wrong, but what you are saying is you are in a gear accelerating and rev the motor to redline. Then, you are pushing in the clutch peddle as you release the throttle in preparation for an upshift. But although the clutch peddle is fully in (the clutch is decoupled) and the throttle is fully released, the motor remains at redline for an instant. But if you do this and you are below redline, then the motor revs reduce quickly and significantly.

When you say you are taking the motor to redline are you hitting the rev limiter so that the ECU is taking over. If this is the case, then the slight delay may be associated with the ECU trying to maintain redline without exceeding this limit.

Bruce In Philly

2009 C2S 192k miles

If I understand you, gas, clutch/no gas, and the revs don't drop as if you are still on the gas? If this is what you mean, I never experienced anything like this nor have I read about this before.

Peace
Bruce in Philly (now Atlanta)

AltitudeRacing

Ok let me explain further, at wot shifting, taking the car to 200rpm below redline and then shifting, the moment the throttle is released and the clutch is pressed within a second of eachother, the rpms climb another 200 or so to redline, this is not foot on the throttle. It feels like i release the throttle to shift but it keeps climbing another 200rpm or so. Clutch should be fine as the car drives perfectly otherwise unless thats clutch slippage symptom.

I think the throttle body feels like its closing late. This only happens past like 7000 rpm

And yes this is a manual.

The car overrevs a bit at full beans.
It has 42k on the clock, just ordered a new TB to install for kicks as this one is prob dirty.

Hwy

85k on mine and nope, there are no rev hangs when I am sending it. Not at 3k nor at redline.

Sticky accelerator pedal?

Yeah- would drive me nuts.

AltitudeRacing

Not sure, doesnt feel like it, only happens at high rpms, the pedal otherwise feels excellent. Car drives like butter. I thought maybe my foot was still touching the accelerator before i hit the clutch but unless i wait like 2 seconds to shift it always does it.
Im going to try the new throttle body, and i have a tune going in to increase pedal response so that might alleviate it. It feels like the car isnt doing exactly what I want at that high rpm and i dont like it. Worst time for a car to decide it wants to rev higher lol. I know some cars have rev hang as an emissions feature but this feels different.

Id like some more advice, how would I know if its the clutch? Last car i had was a 1994 supra turbo which was converted to a track car, and when the clutch went it went. It never had any real symptoms it just kind of started slipping all over the rev range one day. This car drives and feels fine, pulls hard, etc. Its just that pesky overrev.

Petza914

Do you have the sport chrono option? If so, test it in both normal mode and sport chrono mode as the throttle mapping is different between the two.

Other thing you may try is a Sprint Booster. This changes the speed (and in some modes, the size) of the signals from the drive by wire throttle positions sensor to the throttle body. Porsche builds a lag into their drive by wire signals.

If you've been around here a while, you know I'm not a fan of the Sprint Booster the way it augments throttle signals and reduces the feel, but what I've recently understood is that even in the 1:1 mode, it allows the throttle plate to move much more directly with the pedal and although I've not tried one of these yet, this aspect of what it can do is of interest to me.

Here's a video that shows the OEM pedal response lag and how Sprint Booster eliminates it.

AltitudeRacing

Yes I have SC, as i almost only drive the car in sport. I have not tried this in normal mode but it happens in sport. Just tried it again right now.

I also did purchase a sprint booster yesterday as I thought it might help. We’ll see. I do hate the throttle response even in sport so i can at least take one problem on at a time.
New throttle body gets here by weekend so ill try that. The car is due anyways

Petza914

Try normal mode - bet it doesn't happen and one of the reasons we never use Sport mode in my wife's C2S. With what you've ordered, I think you'll get it resolved. Would be interesting to track live values with a durametric and see what the throttle position sensor and throttle body are showing for values when this occurs, like does the TPS drop in values immediately but the Throttle Body stays the same or increases, or vice versa.

AltitudeRacing

As far as I know, the sport mode only alters the throttle response, which means with the sprint booster I should be able to avoid sport mode.
Am I wrong? Does the sport button do anything else? (aside from also turning on PASM). I wish I had a durameteric, but only have the foxwell nt530 on hand right now.

You know, I havent tried it on non sport mode, good idea. Ill take it for a drive later today to test. I really hope it does not do it on that mode, would make diagnostics solved as it would be sport mode pedal map related.

Petza914

From an engine perspective, that's all sport mode does.

AltitudeRacing

Perfect this will greatly help my diagnosis. I tested it earlier to day, absolutely dogged on the car and the clutch feels perfect so I do not think I have a slipping clutch.

Optionman1

Sport mode, at least with a PDK, must do something other than just adjust the throttle response because if you engage it while 100% off the throttle (coasting), the tach immediately jumps nonetheless.

AltitudeRacing

hmm no clue, never driven a pdk car.