Hello,

I have a rather weird issue w a S8 2002 type RZ FD. Its has stock engine and turbos. only mods are a carbon airbox and open muffler. Cat is empty

With the PFC in the car it makes no primary boost, you can go in 5th on a incline and it will max make 2 psi at 2500 rpm

I observed as soon as some pedal is given below transition rpm the line going to the CCA jumps almost to ambient pressure. Sure one would say the issue is the vacuum lines; check valves; solenoid box. But the car has new vac lines, new black solenoid box, new WG and pre Ctrl solenoids and to top it off w the stock ecu the primary boosts totally fine. In 4th there is 0.8 bar at 2500 rpm going on a slight incline. W the stock ecu the CCA keep seeing full vac till transition. The car keeps pressure and vac for multile days the charmbers. KOKO test w stock ecu works fine. once past transition rpm it boosts totally fine w the PFC

It almost seems like the PFC controls a solenoid that the factory ecu does not which robs away most of the vacuum in the vacuum chamber causing the CCA not to have enough vac and opens slightly leaking away boost.

Log and .dat attached.

 

Are you using an S8 PFC?

 

Do the poor man seq setup just to test the turbos functioning., That is pre-control and turbo control wire opened. If this works, then you have turbo control problems.

Or wire the wastegate closed and slowly get on boost to see if boost builds fast for wg control problem.

 

Yes its the S8 PFC

just found the issue. It seems the previous people working on the car had somehow swapped the purge and turbo control solenoid 2 plugs and marked them wrongly. So I just went by their marking and plugged them in the same manner..

it seems the pfc controls the purge in a different way then the stock ecu. When the pfc was controlling the purge it would in reality control the tca vacuum side and this would use up most of the vacuum.

 

Did you by any chance snap a photo of the purge solenoid I’ve found tc2 but can not find any info on purge having same issue