When on boost, it hits around the 15psi mark and then feels like it hits a wall and kind of shudders, almost like overboost cut-out except I've tried disabling all overboost protection and it still does it. Tried using a simple GFB bleed type controller and it still does it although not as quickly.

I have been using a GM boost control solenoid (3 port) but have also tried the OEM one too with no difference.

ECU mods to boost control settings using GM 3 port BCS only make it boost faster or slower but as soon as it hits around 15psi is when it dies.

Plenty of fuel available, tried various timing settings and anything else I could see that would be relevant but no joy.

(And I have checked and replaced all of the vacuum lines etc to eliminate that side of things)

Car is a 2003 wrx, turbo is a VF34, ECU is a Haltech PS2000.

Any ideas??

sell haltech, get verso, fixed

does your vacuum line still have the brass restrictor in it?

get rid of haltech

sounds like a problem with the tune, not mechanical.

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Long live the WRC

Well I tried it with a spare Motec I had in the garage just to be sure and same deal so if it does it with a Motec also, unless verso are that much better than Motec I don't think the Haltech is the problem

No, it only needed that when it was running the 2 port OEM solenoid.

I can't see how the tune would affect the turbo unless the ECU was also controlling the boost solenoid which it was but to isolate that side I also tried various standalone boost controllers with the exact same results.

When the ECU was running everything, my preferred option was closed loop boost control (although open loop was attempted also) but regardless of what duty cycles were used and PID settings the best I could get it to do after plenty of traces and logging runs was incredibly fast boost onset which once this 15psi issue is sorted will be awesome. As far as the ECU is concerned the BCS is operating correctly and it is completely unaware of the drop-out of boost until it happens (i.e. nothing from the ECU is telling it to do anything at the moment of failure) so the only other things being controlled by the tune are fuel and spark, both of which are working perfectly as verified by the AFR targets being met with no need for any O2 correction and no ping/knock being present.

Obviously I'd like it all to be controlled by the ECU as it's more than capable of doing it, I just have to diagnose this issue first and it's just a process of elimination but figured I'd ask here to see if anyone has experienced this kind of thing before.

Looked at more physical aspects?
Wastegate, wastegate actuator, up-pipe size/diameter, turbo itself etc
Have you have this setup working previously? As in, has the issue only just started occuring?

Edit: Isn't your up-pipe leaking? If I wasn't making boost, and I knew i had a leaky up-pipe, i'd be inclined to fix that first.

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Signarape!

well if is the same result on multiple ECUs have you tried eliminating the simple stuff?

Check your plugs, plug gapping and coils.

Also fuel pump and fuel filter.

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RS Liberty - Because WRX's are only good for parts...

I should point out that off-boost and up to ~15psi or 1 bar it runs beautifully, lots of torque, responsive and lively across the entire rpm range

No you have this car confused with my other one. This one (I call whitey) is the white 2003 WRX whereas the one with the leaky up-pipe (I call Darky) is the black 2006 STI

The issue started occurring after a whole crapload of changes so it's hard to try and attribute it to any one particular change, but if I had to choose one change out of them all I'd say extractors I suppose.

I doubt it is the turbo seeing as it is only about a month old but I do have a spare VF34 that I could use to isolate the turbo itself seeing as I guess it's possible for a brand new turbo to be faulty (although unlikely).

Fuel filter replaced recently, not sure how to check fuel pump, plugs are new and gapped properly and no I haven't replaced the coils but I guess it can't hurt to try.

What boost is the tune set at?

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