is this usual behaviour from the S2????

[prj]

Do what Paul said...

[A80Avant]

could be a torn wastegate diaphragm...

[prj]

Possible as well, but why'd it happen right after changing the exhaust?
Sounds to me like something isn't plumbed up quite right.

[Jamo]

Lack of back pressure from the 3" exhaust and no cat, hence no exhaust gasses flowing through the wastegate when open

[prj]

Lack of back pressure from the 3" exhaust and no cat, hence no exhaust gasses flowing through the wastegate when open

No!

Exhaust will not do this, I don't care what you have on there.

[AndyP]

Did I miss something, where did the 30psi figure come from?

[newsh]

OP states that car spikes to 30psi

[newsh]

I agree, unplug WGFV and tell us how much boost you're getting then.

[A80Avant]

it could have happened as wastegate was taken off to do the downpipe perhaps, or just bad luck! i can believe anything about these engines when it comes to bad luck!

[newsh]

The fact that its "chirping" would tend to indicate a leak perhaps?

[Ian Simmonds]

When we plumbed our AAN with a 'Spinked' ECU onto a 3" non cat Ur Single box system in the RallyRep it ran beautifully straight out of the box... I can't imagine the exhaust 'rear pipes' influencing a fully managed engine.

[driftin jo]

I would be amazed if it wasn't leaking somewhere at 30 psi, then again the turbo could be surging if the waste gate isn't opening at all. Something is not right with this though as the ECU should be cutting fuel pump (violent cut of power). I would say you are very lucky you still have an engine.
If you continue to go WOT you will put a con rod through the block for sure.
This needs mapping but also sorting out as the fail safe features of the ECU are not working.

[prj]

Most tunes don't have fuel cut and many have no boost cut.

But yeah, turbo spoolup will be affected a lot more by which gear you floor it at than by the exhaust.
No matter what your exhaust is, you will not be able to have the turbo spool in 2nd like it spools in 6th. This motronic does not have gear detection and it is able to almost perfectly manage boost in every gear, so exhaust is peanuts for it.

This car sounds like it has no boost control at all.

[driftin jo]

he says this isn't tuned .

[prj]

Stock will cut fuel mostly after ~4500rpm.
Sounds to me like there's no boost control.