C7 GrandSport : Manual gearbox swap Z51 to Z06 : Table 20090 not working ?

[Sachs]

Hi,

I have 2017 C7 GrandSport where I already put a Katech stage 2 engine, which I successfully tuned.

I do not like Z51 gearing that comes with the GrandSport, so I bought and swapped myself the crappy geared Z51 gearbox for a Z06 gearbox.

Gearbox is the same, only the ratios are different.

I thought this was going to be very straight forward. Normally I should just have to go to table ECM 20090 in the Trans menu and put my updated ratios.

I did, but it looks like the ECM is not taking the new values. I'm getting " reduce clutch usage -power reduced " messages on the DIC and sometimes DTC " 5th gear wrong ratio " on other.

I data logged everything and :

- Output trans shaft speed is good and consistent
- Clutch position stays the same when it happens
- Calculated ratios between engine rpm and output trans shaft RPM is the same as the entered ratios in table 20090
- Clutch is not slipping even a bit

I'm excluding mechanical or electrical/sensor issues.

I did a test putting back standard ratios in table 20090 and I have exactly the same issue. Which tells me the new ratios are not registered by the ECM when I flash.

What do you think ?

- I submitted a ticket to HP tuners technical support and they answered me they will look into it but I bet it will take weeks or months
- I only tried " write calibration " like I always do. Can write entire change anything and is it risky to do it ?
- Is there something I'm missing ?
- Is there a way to use a M7 Z06 file and flash it to my GS since it's the same ECU, then putting back my tune values in all the tables ? I'm assuming this would create a whole bunch of potential issues because the GS does not have the supercharger and I would be missing several sensors and actuators ?
- I know some sequential swaps on GS, there must be a way to trick the system so the ECU does not look at the ratios ?
- Temporarly is there a way to disable this reduced power mode ? I know I can disable the DTC for wrong ratios but I bet it will not prevent to cut power...

I've been thinking a lot about it lately and contacted some experienced tuners on the forum, I'm willing to pay to get it resolved as I have racing events (AutoX and Roadcourse) next week, but no one is answering me... There must be a solution somewhere, this should be a damn simple swap !

Thanks

[blindsquirrel]

Probably needs a segment swap, there's lots of code behind-the-scenes that isn't reflected in any tables or settings visible in the editor.

[Sachs]

Probably needs a segment swap, there's lots of code behind-the-scenes that isn't reflected in any tables or settings visible in the editor.

Which segment would you swap ? You don't have a transmission segment for manual transmissions...

I found a C7Z file with the same OS than my GS and the files I have :

- System
- Fuel system
- Speedometer
- Engine diagnostic
- Engine operation

...

[Sachs]

By swapping the engine operation segment I was able to get the Z06 ratios in the trans menu. Now will it work if I change all my tables back to LT1 ???

[Sachs]

Answer : it works. Had to rewrite all the tables though.

[Sachs]

i spoke too fast. Running the Z06 program creates all short of other issues on the fueling/TPS and some sensors (knock retard sensors are not working anymore)

Gearing works but too risky for the rest...

I'm back to square one...