A6 2016 C7.5 BiTDI 320 ps slow in low RPMs

[Haudi]

Hi All,

I'm pretty desperate already, would greatly appreciate, if anyone has any idea what could be causing this issue - basically my A6 3.0 BiTDI 320 ps has been accelerating very slowly from steady rpms to 2000. It takes like 2-3 seconds to reach 2000 RPM and afterwards when the big turbo takes over, no issues. The car was tuned with Stage 1 chiptuning to 410 hp 800 NM, however I have removed the tune as I though this could really be causing the issue.. The car is now DPF/Adblue off with DPF removed and back to stock software. Apparently the issue is still there.. I was advised to take off both turbos and send it for test, I did it and the response from the test service was that it looks like the previous owner of the car changed the Actuator of the small turbo, which led to some difference in the small turbo's operation, so they suspected the issue is coming from there, however after fixing the geometry and placing back the turbosystem apparently the issue does not come from there..

Next think we did was to isolate the EGR and check if there will be any difference - not really, still getting quite slowly from 800 to ~2000 RPM's while when testing one of my friend's A7 BiTDI 326 hp his directly jumps from start to 2k RPMS without hesitation.. There are no errors on the car, nothing comes on diagnostic, my tuner also looked the car on VCDS and can't seem to catch anything. We checked all vaccumm points for leak and can't find anything. Only thing I have reparied changed on the car apart from the turbo geometry calibration is replacing the Crankcase Ventilation System both filters and repairing 1 of the injectors and getting the other 5 checked.

If you guys can recommend anything, I'd greatly appreciate it. 

Thank you in advance!!!

Edited September 9, 2023 by Haudi

[Greyanglia]

Just a sympathetic note and hope you've got it sorted. I have the same engine in the Allroad and although I'm no mechanic does it show the lag in both D and Sport? Only ask as it sounds software related I think. Either way, good luck in getting a fix.

Michael