Chad!

Ow do chaps,

Now then, I am a little concerned about this problem because I have absolutely no idea why it's doing it. Basically at full throttle, not top speed. The boost goes ape. It fluctuates anywhere between 10psi and 18 psi. The needle on the boost gauge jumps up and down like it's on something. Anyone have any ideas what could be causing it? It has gotten worse over the last 3 or 4 weeks. At first it was just dropping off boost for a short while and then coming back on boost, but now it fluctuates a lot of the time when on near to full throttle.

Car is MY99 UK turbo.

Cheers,

Chad.

swifty.....!

iTrader: (4)

had this on a few gauges for me it was the gauge i.e when you put foot down full boost then needle goes off on one. but always best checking pipes for splits etc.

Chad!

Hi,

Thanks for the reply. I wish it were just the gauge acting up. But when the gauge shows fluctuating boost, I can tell by the way the car bahaves too. I can actually feel the boost coming and going.

Anyone??

Thanks,

Chad.

Chad!

Anybody?

Someone must know. Cause I don't.

Scott.T

iTrader: (2)

clean the vacum/boost hoses that connect to the turbo, actuator and boost contrl solenoid nipples. You may have a slightly block restrictor valve which will cause boost to overshoot target. The ECU will try to pull this back and fail, hence the fluctuation.

ReggieMY99

Try cleaning your boost solonoid, common problem with fluctuating boost, have had it myself, now use a manual boost controller

anyway put the car in to diagnostics mode

http://www.saxonfields.freeserve.co....iag%20Page.htm

locate the boost solonoid and take of the pipes comming from it, when you put the car into diagnostics mode via the above link (put the car into ignition, DO NOT START THE CAR) the solonoid will start clicking like mad, your fans will come on and go off again, just ignore this, use some brake cleaner and spray it into the solonoid while its clicking away, let it sit for a minute and wipe it clean with a dry rag, take the car out of diagnostics mode and attach pipes again, take it for a drive and see how it acts up

Also as above check for leaks in pipes around the turbo area, if they are orginal they might have been fried good and small cracks appear that wont be visible to the eye. Area around turbo gets very hot.

hope it helps

Chad!

Cheers for the replies guys. I'll have a check round at the weekend. The restrictor that is mentioned, where can I expect to find it? Can someone tell me which hose/pipe it can be found in? Like from actuator to boost solenoid for instance.

Cheers,

Chad.

ReggieMY99

It should be located between the compressor housing and T piece, small brass restrictor should be inside at one of the ends

Chad!

Cheers mate, I'll give it a go.

Chad.

SiHethers

Clean the boost solenoid is a good start.

More info on your car spec would be useful....

Si

Chad!

It's standard. Just an MT99 UK Turbo as said above. It is running higher boost than standard but I have no idea why. I'm assuming it's been chipped or something at some point? I know it's nothing to do with the actuator as I have replaced the turbo since having the car. I don't know where the ECU is so I can't really look.

Chad.

Chad!

Well, I had all the pipe work off at the weekend and gave it a good clean. Including the little brass restrictor. The boost seems to be a lot more stable now, although it still doesn't feel smooth. It feels like the boost is lumpy... Anyone else had this and know why it's lumpy on boost?



Chad.

Scott.T

iTrader: (2)

It's sounds like it's had a tek remap then.
What does it normally boost to. if standard it should be around 13.7psi (approx 0.9bar)

IIf it's standard and f you changed the Turbo did you also change the rubber hoses where the restrictor valve lives.
If so you may have the wrong restrictor. The smaller the restirctor the more boot it will 'TRY' to achive.

If it only does it in 4th and 5th then I expect that the Boost Control Duty may be set slightly too high (if it's been remapped) or the restrictor is too small (if it's standard) i.e it over achieves the target boost and the ECU pulls it back, then it over achieves and pulls it back and so it goes on......

Chad!

It normally boosts to around 17/18PSI. It seems to be boosting ok at the moment. As I said it just feels a little lumpy. But as it has had a good clean I don't understand why it is lumpy and not just a nice clean boost. As far as I'm aware it hasn't had any remap at all. BUT, why it's running such high boost has been something I've not understood since I bought the car. Any help with this lumpyness will be much appreciated because I don't know enough about Impreza's to know why it would be doing this.

Cheers,

Chad.

d5hof

you sure you don't have a decat system? if you have a decat system and induction kit it may mean you need to re-map the ecu, I have a decat system and K&N typhoon induction kit and damp valves and I experience the same problem, I spoke to Andy at scoobyclinic and he said its because i need to re-map the ecu as it now creates a lot of boost and then restricts it thinking it still has the cat, so on full throttle my gauge goes berserk!!!
I'm hoping to go for Apexi ecu and boost control

Chad!

It is a decat, no induction kit though. But it was like that when I had it a year ago and it's only been playing up recently. The fluctuation seems ok now, it's just the lumpyness.

Scooby-Enforcer

It could have an FCD fitted, and a Doze device, check the Doze is sealed properly and not leaking , use plumbing tape on threads if you do have 1 ??

Chad!

Doze device?? Do you mean a dawes device? If so then, no it hasn't get one. Everything mechanical wise to do with the turbo is standard. The only way I can think of that the boost has been increased is electronically.

old boy

Hi, I had unstable boost on my 99 my RB5 it would boost at different figures in different gears. Fitted a 3 port boost sensor and had a tweek of a remap and its fine now!!