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Intermittent boost loss


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so as I have been putting the car under a bit of pressure, sometimes it will cut my boost psi from the usual 15/17 down and hold it at 5/6.

So I searched for boost leaks, which I didn’t find. I then disconnected the negative terminal to attempt an ECU wipe and it worked! Back up to normal psi....temporarily 🙄

is there something I am missing here? It is essentially going into limp mode if I get into high rpm boost like the ecu is trying to save the engine.

im running a 2nd cat decat, 2.5 inch straight through with an STi backbox, air intake and an atmospheric BOV.

is any of the above parts the reason for the limp mode? Or do I need a remap?


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30 minutes ago, savage bulldogs said:

What year and model is it bud ?

Do you mean its got a decat downpipe ?

Has it been mapped , cos if not its probably overboost causing limp mode , due to the extra air from the intake and less restrictive downpipe

It is 2005 WRX mate, and it’s the second cat that has been deleted, not the first one after the turbo.

nah it’s not been mapped as far as I’m aware, but then I’m not the first owner!

Yeah, I’m thinking it will be over boosting too due to less restriction, i think a remap would be the safest idea!

thanks for your help :)

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Think you used to be able too buy a Bluetooth odb2 adapter off eBay and download a app for your smartphone (torque app i think) That reads ecu codes.

Hopefully one of the newage boys might be able to confirm if its still available and works on your model .

As the ecu might be cutting boost for a different reason , so knowing if its storing any codes would be a good idea before booking in a expensive mapping session.

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I ran with the last cat removed for about 9 months without a remap and encountered no issues.

Air intakes are known to mess with the maf without a remap, maybe put the standard airbox back on and see how it behaves

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So I started to mess about with the poor man’s bov to see if that was the cause of a leak/issue. I took it off completely and put the standard recirc valve back on and the car runs beautifully, no issues at all.

i was reading into the bov (or similar one as I didn’t buy it) and I think the issue was how much psi it could handle. It looks like most of these cheapy bovs can only handle 15psi at most and on WOT with better flow I was up past that, causing premature boost loss.

note to all, don’t use cheap bov’s, and if you do, make sure it can handle over your boost pressures :)

thanks to all for your help and suggestions!

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