My car has been in the shop since last August with this issue and I can't take it anymore. I put some Xona XR 1000 on it and refreshed the gearbox. Now, the car does not respond to tuning with Cobb AP at all. Loaded several tunes and it simply defaults to 17-18 psi 690 whp and almost 600 wheel torque. Tried to load an OTS map, car doesn't respond at all.....to anything, turn of key, nothing. Tried bypassing the N75, it did finally go down to 11-12 psi. Put a new N75 in and it does the same thing.

What things can cause the car not to respond to tuning at all? I need my car back......need to go racing.

 

venturing a guess..

an overworked old and unresponsive ecu? ecu's are not normally considered "wear items", but how many different switchable maps can they handle over 20 years, would be my question.

 

Clogged cat / exhaust?

Wastegates improperly adjusted?

 

Ive been told that everything has been double and triple checked. Got the turbos and wastegates from Sam at By Deisgn. Taking the ECU out and sending it off for inspection. The zero response on the off the shelf tune makes me think the ECU might be the culprit.

 

What wastegate springs are you running? My guess is you have the springs that Tial ships these turbos with which makes tuning very difficult if not impossible if you are looking to have good throttle modulation. I've switched both the WG springs in my old XR980s and the XR1000s to a substantially softer spring. Virtually everyone I know that runs these turbos on a road course has done this. This is the dyno sheet on my old XR980s and the throttle modulation and power curve is very similar to an NA GT3 engine, albeit slightly higher up on the scale but makes for excellent drivability on track. This is at 1.3 bar on a 91 octane map.

Look at your logs. What is your N75 duty cycle? What is your requested boost vs actual boost? What psi do your wastegates begin to crack at? What psi are they fully open at? What is the overall wastegate arm travel? That will tell the story. I highly doubt your ECU is faulty....

 

Markski is helping me out and he said the exact same thing regarding these springs. I ordered the softer green springs from Tial. I'm using Cobb AP... is the N75 duty the same as the wastegate duty cycle on the log?

 

This is probably not the cause of the issue, but I have been having a difficult time loading any maps from Cobb. It states the latest map has loaded, but I know it is still running the previous map. Other times it just errors out while trying to flash. It started happening after I upgraded to the latest firmware and software few months ago. I fixed the issue by loading a beta firmware/software version.