Boost issue!
 

Hi I'm new to imprezas and turbos in general, I have an issue with my 2004 WRX it is running 260bhp with a print out has and exhaust and a panel filter, iv only owned the car a month and it drives great iv fitted a boost gauge, it boosts to 14-15 psi, 1st gear pulls nice boost picks up and holds, 2nd gear act's the same, I go into 3rd and boost picks up to 15 psi until I'm at about 5000rpm then boost drops to 6psi and after this happens no mayer how hard I rev or what gear I'm in I can not get over 6 psi of boost, I belive this is limp mode no EML light on, if I turn the car off and on all is back to normal I can boost around in 1st and 2nd then give it a little blast in 3rd as long as I don't take it to far up the revs.
Any ideas why?
I am running it on 99octane and iv tryed a standard recirc still have the same issue.
Thanks all

The td04 turbo runs out of puff higher up the rev range

Yes but the problem is once this happens the car will not go over 7psi no mater how high or low the car is reving.

I have a manual T boost controller in the garage I took off a car years ago, could I bypass the BCS with this to see if it makes a difference, just set it to 12psi or so?

Sounds like the ECU is cutting boost for a reason and putting it into low boost mode. There has to be a reason for it to do this, so to bypass the BCS with a controller and set it to 12psi wouldn't be wise in my opinion. You're not fixing the issue, your making the car run with more boost with the issue.

If the BCS is allowing the engine to make boost sometimes just fine then I'd say the BCS is not the problem. It will be somewhere else.

Okay, iv tryed it again today changing up around 6k (just before the boost tails off) pulled through nice in all the gears, it's just very intermitent, is it worth cleaning the BCS and do the restriction pills ever need cleaning?

What fuel are you using in the car ?

Might just be coincidence, but pretty sure 7psi is exactly wastegate pressure, so problem with BCS is probably not a bad shout.

Otherwise, 99% of boost issues are caused either by pressure leaks or ECU cutting.


Edit: if your restrictor pill was clogged, you'd be at risk of excess boost spikes, not failure to reach normal boost, so unlikely to be that.

I've got a similar problem with my car. Haven't really been able to pin it down either.