ADU Plumbing

[le mans]

My RS2 has an aftermarket ECU (Link). I caught up with Nik yesterday and we compared notes. So the standard plumbing in the RS2 is a bit different from mine. My car has a line coming off the top of the waste gate to the boost control valve. Standard car has none. Any thoughts on whether this looks correct or not? If not, how should it be hooked up? Probably not relevant but I believe the car is running a mafless tune - it uses manifold pressure for the load tables as far as I can see. My car is boosting OK but not very smooth and not hugely strong when on full boost. Sometimes it stutters. It is silky smooth off boost and on part boost. Nik's is much stronger on boost. Could be a tuning issue but wanting to eliminate obvious issues first. I haven't had a boost leak check done (yes I know!)

Diverter valve from top (looks OK):

Boost control valve and plumbing:


Also plumbing at the back of the engine is different and there as an additional 'box' mounted:



Can anyone educate me?

[UrS4boy]

Definitely NOT stock ADU plumbing. I have to bite my tongue and not say what I think of what you have there.

Cough <hack job>

[le mans]

Ha, well I suspected as much. I would like to get it tidied up though.

[Error404]

My 2c - rip that **** out and revert to the (excellent) standard system

[le mans]

My 2c - rip that **** out and revert to the (excellent) standard system

Yep fair comment.

How much work in replacing everything? What do I need? ECU, loom etc...?

TBH I was just wanting to get my head around what has been done to it, especially WRT boost control. Looking at the aftermarket MAC boost control valve from the front:
- Left line goes to connection on engine case
- Right line goes to top connection on waste gate
- Bottom line goes to recirculation valve

[quattro-nick]

-normaly the recirculation valve or dumpvalve is connected to intake manifold(the little vacuumtube)
-by a origional n75 valve goes one connection to turbohouse(for boostpressure),one connection to lower chamber wastegate and one connection to intakehose turbo a or free air

http://s4wiki.com/wiki/Wastegate_bypass_regulator_valve

[Error404]

Unless you have two boost solenoids, they it looks to me like they have bodged the boost control by feeding boost to the top of the wastegate to keep it shut, effectively doing the same as a stiffer wastegate spring.

Looks like you will need to repair whatever butchery has been done to your engine harness (hopefully not too much!) or replace the engine harness if necessary.
Fit a stock N75 valve & plumbing and stock RS2 ECU or one with a proper map from someone who knows what they are doing!