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Boost issue

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I have been treating my wrx with a bit of respect and learning how she behaves over the last few weeks, i have very rarely stamped my foot to the floor for a couple of reasons, i havent needed to, and the roads around my area have very few overtaking spaces and i dont want to risk anything in a car im still learning. This is not to say i havent experimented when its safe to do so though.

Today i noticed a strange thing when i overtook someone, went up to 5th put my foot back into the floor until i was safe then eased off.  As i passed the halfway mark back to 0 throttle all of a sudden i gained a load of boost and it surged forward a bit until i came off some more throttle.

My car seems to love living in the first half of the throttle. I only have seat of the pants figures to give you but it seems when you put your foot to the floor all you use is the 2.0 engine and less effective boost, i cant say how much because this is all still so new to me, but the difference is certainly noticeable and worthy of the word 'surge'.

Ive done as much browsing and searching as my overtired brain can cope with tonight, but all i can find is some one who seemed to have an over fueling problem and boost cut kicking in.  Mine doesnt die or jerk or judder like his did though,  i think im increasing in speed quite rapidly until i reduce throttle and use the first half of the distance your foot can travel.

Does this mean anything to anyone? Has it been remapped to this? Is it a failing part, the actuator? Is it over fueling? 

Im booking it in for a once over by my mechanic in the next few weeks when he has a free moment. but in the mean time if anyone has any info on the weird boosting i would be grateful.

Good news to finish on, ive just bought a Hayward and Scott back box for that classic scooby burble ive envied for years  ;D

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Could be a stuck wastegate, dirty soliniod or over boost caused by a decat ? (If you have one). Possibly even a sticking throttle ??

You'll know if it's a boost cut as you'll get boost when accelerating then, it will be like someone's turned the car off and back on again for a second.

Sent from my SM-G930F using Tapatalk

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Boost will come in properly over 3500rpm, so as you lifted A little off the throttle you may have been crossing that point and using the turbo. Play around accelerating up to about 5000rpm with foot to the floor and foot halfway and you will get a feel for it.


the tachometer is your friend and you will start to learn where you are on and off of boost. Better yet get a boost gauge and if there are any turbo issues you will soon see.

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Thanks for the reply guys.  Ill try and check the wastegate and solenoid out before it goes in for a check up.

I am able to replicate the issue anytime i want if the straights are clear, because it happens at higher speeds and revs. Its not that i dont know when boost kicks in unfortunately, that would be an easy fix. We are talking over taking speeds or dual carriage way speeds in 5th.

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I think i may have had some developments in this area over the last few days.

First i replaced the air filter with a cosworth high flow flat panel filter, when i pulled the old one out it was only slightly dirty on top, but underneath it was black, the dirt came off like oil, my hands where filthy, inside the air box underneath the filter was filthy black aswell, so i cleaned it all, checked the pipes where clean and clear and the maff, fitted the new filter and wow what a difference.  There is a noticeable difference in smoothness, the turbo is slightly more responsive, everything is a bit sharper, but i can now do 60mph at 2750rpm approximately instead of 3000rpm on boost.

My second hand Hayward and Scott turned up the other day, i went to fit it today, pulled the old back box off and found out that new back box doesnt fit, despite being told it came off a 1997 classic but was being used on a bugeye fine, it cant have come off a classic, the rear hanger (after the silencer) is in the wrong place.  Also i noticed that i wouldnt be able to fit it even if it was correct, as the pipe system i have is either 2" or maybe 2.25"??? 

This is wrong as far as i can find out, I am under the impression that non turbos have exhausts that small but turbos have 2.5" or an upgrade to 3".

So, the problem could be not enough air, and reduced exhaust gas flow, at high rpm the car cant get rid of it fast enough?  So, i am now on the look out for a turbo back system with a sports cat :cool:

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