Hi Guyz

Got my scoob about a month ago which had a bailey VTA dump valve on it. Having read all the negative info on here about them and only wanting the best for my new prized possession I bowed to the greater knowledge and put the standard one back on today.

Went for a little drive after and now have a boost issue. For example coming of a roundabout in 3rd and opening her up the boost gauge flies round to around 19psi (ish) then bounces back to about 15psi pulls back up to 19ish and holds there fairly nicely.

Firstly is 19psi about right. I say (ish) because I wasn't out long and it's tricky blasting down the road whilst watching a gauge!

Secondly, any ideas for the boost slump?

Is this boost spike perhaps? Or would a spike make the boost 'spike' over normal Psi then settle back down rather than slump? Leaky hose somewhere? Strange how its just started after fitting oe dump valve back on? Unless I nicked a hose when fitting it. Was actually a right bitch to fit. Trying to get that clamp on the hose

Any ideas welcome. Want to get it mapped soon but obviously need to sort this issue first.

Car is a 2003 STi UK PPP cat back exhaust, otherwise standard.

Thanks

 

if it doesnt run right with it off, put it back on and see how it runs. despite what seems to be claimed not all react badly to them, also some get mapped for them.

 

did you put the small vac line back on the side of it?

 

Tidgy - car wasn't mapped for it. I know that much. And no word of a lie, despite the boost issue the difference to the car is unreal. It was a little rough and gear changes were awful. Almost threw you forward when you changed gear. Now it's all as smooth as anything. Totally different drive, like a different car. So don't really want to put it back on.

Gaz- yep small side hose all connected up. I did swap the re-circ hose clamp for a jubilee clip as I just couldn't get that clamp on. But shouldn't make a difference with that.

 

Just been sitting here having a good read round the ole web for clues...

How violent is the fuel cut? On my old wrx it was savage and very noticeable. Has it been toned down a bit on the newer cars? I'm wondering if its spiking and fuel cutting?

Should the oe re-circ valve have a gasket? Or just bolt straight on? It almost looked like there was some sort of gasket fixed to the inter cooler? Like a black silhouette?

Also I think it was running very rich. Smelt very petroly most of the time. Checked my oil today and it stank of petrol. Would the Ecu need time to adjust to the change? Think the VTA valve had been on the car for some time.

Cheer for any help

 

Could be the Valve sticking. Maybe worth taking off and blasting with WD40 ( as not sure if OE item can be dismantelled) and manually operate it to clean any corrosion off then wipe it down to remove as much as possible.

 

Hmmm...good thought! I'll try this.

Got to be honest I'm not too sure how it all works. Does the valve only open when u change gear? Or would it open when boosting up?

 

when i fitted a jubalee clip on the return hose the clip pushed agaisnt the throttle sensor connection (i think it is) and caused issues (it cut boost) was violent though but just check your clip isnt pushing agaisnt anything

 

Thanks mate, another good shout. I know the sensor you mean and it did take a fair bit of knocking whilst fitting the DV so could easily have caused damage to it or loosened it etc. I'll check this as well!!

How quiet are the standard DV's? I couldn't believe how quiet it was, I couldn't hear anything? Maybe it's not opening at all? I think it's been sat around for a couple of years.

 

Thats correct. You wont hear much at all from the o/e valve. Yes there is a gasket between valve and intercooler. If you havent a good tight seal it will be leaking boost

 

Ok cool thanks. Hopefully it is as simple as that. Like I say it did look like there was a gasket but like it was stuck to the intercooler. I didn't want to pick at at incase I damaged it. I also went easy on the jubilee clip as didn't want to damage the hose! Might need a few more turns of the screwdriver!

Cheers folks. Gives me a few bits to check on Friday when I'm off!!

 

So a quick update incase anyone else has same problem.

Followed all the tips below:- Took the DV back off, cleaned it up with WD40, wiggled the little sensor on the inter cooler pipe (which wasn't quite on properly), soaked the gasket in WD40 whilst i did the other checks, put it back on, made sure the jubilee clip was nice and tight and went for a blast..........................

Running sweet, no stutter, no hesitation and boosting smoothly around 17 psi

My money is on the slightly loose sensor. I also made sure this time that the jubilee clip was clear of that sensor.

Cheer fellas. Very pleased. Time to sort out this remap!,

 

Dam it! Spoke to soon!

Was fine this morning. Went out this afternoon and was fine To start with. However, floored it through a tight corner and it hesitated. Now it's doing it all the time again. I say all the time but just when accelerating hard.

 

Perhaps the standard valve is knackered or youv got an air leak somewhere. Something simple like a loose or split vac pipe could cause it.

 

Weird how it was fine though for quite a while today then came back?

Loose or faulty sensor somewhere maybe?

If it was a split hose or such like would it not have been problematic all day?

 

Have you tried a different valve, they can stick intermittently. Is it just a hesitation or fuel cut due to overboost? Air temps were higher this morning than this afternoon this may be relevant.

 

Pretty sure it's hesitation. Seems to be happening just as boost starts now. Where as when i wrote my first post i reckon it was spiking and was more violent. Boost gauge was flying round to 17+ before it stuttered previously.

Next step will be to try another DV.

thanks for your input

Will keep you posted!

 

Deffo try another DV, could be the spring has weakened or snapped so that boost pressure is opening the valve. If it is a VTA then this would be p'ing off the ECU| as the MAF sensor tells it one thing but the DV is dumping some air resulting in a very rich mixture. At worst get it on a rolling road for a diagnostic.