Strange fluctuating Boosting issue

[S2 Ant]

Hi all, car has started having a weird issue lately... first noticed it the other day when driving... was on the motorway, applied a bit more throttle but still part throttle and it wouldnt stay steady... it fluctuated between 5 and 10 psi and you could hear the fluctuation from the exhaust note as well.

Been out in the car today and the partial throttle issue seems less pronounced, but as i know its been there i've been looking for it and its still like it but to a lesser extent. Applied more throttle to see what happens and the boost spun round past 25psi so immediately lifted my foot off the loud pedal.

Had a look over it but cant see anything up with any intake feeds being lose or anything like that.

The car is Revo Stage 2, 48k miles, BSH Intake kit and Miltek TBE and has a Forge DV.

I've checked the car with VCDS and there are no faults showing on the car at all which doesnt help.

Anyone have any ideas on what might be causing the issue? My thoughts were perhaps sticking DV?? Do these cars have a wastegate and as such a waste gate frequency valve that might be sticking or not running right??

The only other thing I can think of was as i mainly do short trips i recently checked the oil and needed to clean that mayo crap off the filler cap, but the oil is fine and coolant fine so nothing untoward there.

Not sure what else might cause this, so any help much appreciated.
Cheers

[RedRobin]

.
I recently had the same problem and I'm also Revo2, Milltek TBE, Forge DV, but Forge Twintake CAI and 90,000 miles. It turned out to be a coilpack on the way out and was confirmed in VCDS.

It might be plugs though. When were they last changed? I change mine every 20k miles - Advised to do so on a tuned car.

Having a boost gauge really helps to see such an issue.

[S2 Ant]

I'd need to check the service book, i'm intending to book it in for a service soon anyway as its almost 4yrs old and switch it to T&D instead of longlife as the car doesnt do many miles.
As I say tho, nothing showing in VCDS and the boost spiking above the normal 21ish psi that it was usually running on WOT made me wonder if something was up too.
I'll take the Mrs out in the car with VCDS and do some logging to see if it shows anything up, but havent had any misfires reported etc.

I guess to add on that i've not been running with an engine cover for the past few months either as the intake was fitted and i've not dremmeled up the one i have yet, so the coilpacks will be more exposed.

[RedRobin]

I guess to add on that i've not been running with an engine cover for the past few months either as the intake was fitted and i've not dremmeled up the one i have yet, so the coilpacks will be more exposed.

....Interesting what you say about an engine cover protecting the coilpacks against the elements. An engine cover does show up any splash marks etc as evidence but I'd have thought the coilpacks were well enough protected even without an engine cover.

[GTIjames]

I would have a look at your forge dv it might need servicing - clean up and re-grease, forge supply a kit

[S2 Ant]

I would have a look at your forge dv it might need servicing - clean up and re-grease, forge supply a kit

This is kind of what I was thinking, esp with the cold weather and minimal usage and only on short trips so as not to warm things up properly, I was thinking it might have got a bit sticky perhaps or frozen in a position and damaged part of its internals when getting unstuck.

Does anyone know if there are any VCDS logging options that might help better identify possible faults?

[chungster]

might be stickey wastegate actuator...or N75 valve (the thing that controls the DV)

[cmdrfire]

forge DV or charge air sensor on the way out?

[S2 Ant]

Just to dig this up as i've finally had it checked out by a garage as i had today off work. They've told me the Downpipe has a crack in it causing some of the gases to leak... Could this cause the problem i've described?

If the lambda's are not getting the readings they expect between the 1st and 2nd due to a leak would that mess things about like this?
Just wanting to confirm the fault before looking to shell out on a new downpipe or see if this one can be repaired etc.

Cheers

[PDT]

The difference in readings between lambda 1 and 2 wont cause the issue. Get it fixed though before hunting for other causes.

Did get your PM, will have a word on Monday and see if milltek will help you out with the issue  

[S2 Ant]

Well, just to drag this one up, i finally took the time to investigate this myself today (The car is never used so its been kinda put off until now)
And a quick look turns up this..... So, for the moment the intake kit is off and stock intake and engine cover refitted until i get a replacement for the bung.

The problem came about by the edge thats been pierced rubbing on the sharp edge of the brake fluid resevoir.

The intake is the BSH Intake, the leak caused by this split wasnt enough to cause the car to log a fault

[bacillus]

Maybe you should try the rubber off of a leg of a B&Q chair like TC did with his ITG K04 intake... 

[S2 Ant]

Not a bad idea that, i need to sort something now i've had to rob the car of over 20bhp by refitting the stock filter and engine cover lol

Also, that happened in less than 2000 miles of driving! I think it can be avoided when i refit it by not sinking the intake pipe as deep in to the joining piece that connects the metal pipe to the turbo. This should space it enough to not rub i think (hope!)

[vRSAlex]

On the exhaust side of things, im yet to have a car come through with a milltek dp thats not blowing on the turbo flange :(

If im fitting one that ive supplied then i re weld the flange.

Nice easy fix on the intake kit.  The car wouldnt have known what was happening with the maf readings being all over the place.

[cupra_k1]

On the exhaust side of things, im yet to have a car come through with a milltek dp thats not blowing on the turbo flange :(

If im fitting one that ive supplied then i re weld the flange.

I'm pretty sure my Milltek Downpipe is blowing. Is it the welds on the flange that have broken on the ones you have seen Alex? I really need to take a closer look at mine.