TCU is back in with the M-Engineering PDK tune.

My creep is back. I really missed that feature, as no other car had it, it feels special again when parking.

Everything seems smooth. I haven’t had a chance for a decent run yet. Just heavy traffic driving. So no Sport plus yet. I’ll try and get a better run today.

 

Ok, so I believe I have finally uncovered the root cause of the dreaded 3rd to 4th shift issue.

I also know why no one to date has solved it.

They have been barking up the wrong tree. You don’t need to neuter the tune.

If I come straight out and say what it is, everyone will say its obvious, and yet…..🤣.

The Patient becomes the Dr, after they have been diagnosed.

Insert your guesses here and I will drop further hints and let you know if you are warm or cold.

 

Hi 4point0 im glad it fixed your problem ...even with my dodson clutch maybee iwill need a good tcu upgrade...i will see how she does when i crank up the boost...

Now crank up the boost and see what she can do now👍

 

Is it something to do with the speed you are at shifting 3-4 vs 1-2/2-3? I would have guess its a clutch pressure thing because at 3-4 the clutch is likely under more load than 1-2/2-3

 

Didn’t M-engineering say they solved it? I’d guess it’s the torque limiter from the ECU - and the solution is to increase the torque limit instead of reducing torque.

I’d guess 3-4 is an issue because of the gearing ratios. It’s not a problem for 1-2 and 2-3 because those yield a higher rev range at full throttle, so less torque. But 3-4 dumps to a lower rev range so the turbos create too much torque for the standard ECU torque limit.

This is my guess because with a manual, APR-tuned Carrera T, which I believe has the same or similar gear ratios as the GTS, if I shift 3-4 at 7,000 rpm the power drop is noticeable vs shifting at 7,500 rpm. That 4th gear power is significantly higher with correct shifting — something the PDK can do every time.

 

Its not tune, its not torque limit and its not clamp.

I’ve played with all of those.

I put the M-Engineering PDK tune on. The First 15min session was mint. Zero issues. Shifts were slick including 3rd to 4th.

Fast session done. Pitted. They run slow guys 15mins. Then passengers 15min, then the Back to the fast guys.

The first time i hit the straight 3rd hits rev limiter. Damn it, its back.

I always said the issue was intermittent. I’m kicking myself I didn’t realise why earlier.

 

I was reading a thread where a few guys got a “Transmission over heated fault” at the track.

They installed the centre Radiator and never got the fault again. You should be shouting AHA!!!

I have the PWR front radiator and never had that fault.

I did get a “Front Diff Failure” which is hilarious as mine is RWD and I don’t have a front diff. Again this is the car crying out that the oil temps in the diff were too high. AHA again.

OS Giken fixed the diff issue. Then we have increased power with the M800’s.

It’s HEAT! The factory transmission coolers are water to oil. They are using hot engine water to cool the transmission. Engine is hotter with more power and the cooling of the water is less efficient.

I’ll up grade the side two front radiators to PwR.

I’m looking into the 2-Rs to see if their trans coolers are different or the same. Then I may get a custom Aur to oil cooler out front. Maybe split centre one and make it a dual, air to water and half air to oil.

 

Cooling brother. In the end, I may need to spring for Dodsons as well. But with more cooling, it should help delay the inevitable.

I am thinking TiAL M800’s are not big enough 🤣

 

My 3rd-4th shift "balk" was with the 93 Cobb/Mitch pro-tune, and I only used that tune on the street. Oil and water temps in the 220 range. I'm on the APR 93 tune now (130.9 in the 1/4), and have never had the 3-4 issue. After 21 track days and oil temps in the 270's on hot days.

 

PTS-BRG had the issue on his GTS4 with COBB, then changed to APR and after many revisions, still had it.

I am highly tuned up with E40 and M800's. The fact that it was completely gone and shifting perfectly first session (With new M-Engineering PDK Tune), but when I went out again heat soaked, it was back like it was never gone, means one thing. HEAT. It was a very hot day. It's always hot here. But Summer is shocking. My Stock side to radiators are damaged from when I ran the Stock open GTS bumper. It was always my intention to replace them with the PWR Up graded ones. So I am fine doing that first, now that they will be protected with the GT3 front bar and mesh.

I'll keep going down the cooling path and testing to see if I can get 2nd session and then all day, without having it. Anyone can back the tune off. I want to turn everything up more, not back it off. So this needs to be solved, another way than backing the tune off. The M800's aren't out of puff yet. If they run out, I may go to G25-550's. I really thought the M800.s would be tyre fryers. But they aren't.

 

Hey 4.0, any guess as to why the Turbo S cars don't have the 3-4 shift issue?

I hit torque limits which needs an ECU reset to get the Sport+/Sport/Launch back. Never a shift issue.

 

They have more power from stock. GTS we have added 50% more power, which is a lot more heat.

 

Interesting... I remember when I had a GTS that was pro-tuned by mitch my car never had the 3-4 shift. Others with the same tune on their GTS did, and I lived in a hotter climate.

 

The problem has only ever been intermittent. Most if the time it was fine. Thats why its been so difficult to track down as you forget about it. So people could have it and not hit the point where it triggers. Ie not get it hot enough to happen.

It appears 2-RS has same PdK coolers as GTS. So this is good. By making the front radiators more efficient, it should help. 2-RS has wide mouth to let more air theough the front radiators. I beat a tuned 2-RS at the track when i was on stock turbo’s and his excuse was, he had shift issues. I never thought much about it at the time. But it is interesting.

 

I added the center radiator and upgraded the outsides to CSF in August. For oil temps, no issue with the 3-4 shift after switching to APR tune.
I was a little disappointed in the results after hearing glowing feedback from posters about adding the center.
If the air temps are above 80deg, I still see 270 oil temps after 5-6 laps.
The change I see is temps come down much quicker following a cool down lap. Down to 230's when I get in the pits.
Your results may vary, I'm highly tuned/modded