[_AJ_]

I fitted a Forge VTA dump valve a few weeks ago for the novelty factor mainly, and although I didn't get any idle problems, I did feel that it was hesitating slightly when changing gear, and could be a little rough occasionally, on part throttle.

Anyway, a few days ago I decided to put the stock recirc valve back on to see how it compared, and I found an oily, gunky (technical terms... look them up) residue in the blanking plug that slots into the pipe just before the turbo. Shining a torch into that pipe also reveals a light film of the stuff there whithin.

I have no idea where it's come from, and I was hoping someone here might know? I'm pretty sure it's as a direct result of the BOV, but the only place it could have come from is through the turbo the wrong way!?? There's nothing in the filter element (standard induction), or the bottom of the air box or anything like that. I know it wasn't being produced while the factory recirc valve was on, because it was clean and dry when I took it off, and it's clean and dry a few days after running around with it back on.

Any ideas?

 

[xlr8]

am assuming that the Forge is an atmospheric BOV & not re-circulating version ?
...in which case the oily residue will be generated from fumes/interaction with air etc not being 'fed back' into the closed-loop system

think along the lines of an 'oil catch tank'
- fumes in...liquid out

 

[_AJ_]

I fitted a Forge VTA dump valve

Yes

I must admit though, I don't really understand that... where are the fumes coming from... the oil that lubricates the turbo?

 

[xlr8]

mixture of moisture/fumes = oily residue
connections for the bov are:
*air pressure from your intake manifold via small hose
* boost pressure via turbo outlet pipe - exhaust
* turbo inlet pipe - air
also, as far as I can remember, there'll be a link in the circuit to the crankcase breather = more fumes

 

[_AJ_]

...but do you know why it would collect there with the VTA valve, and not the factory recirculating one?

 

[xlr8]

the VTA = vent to atmosphere
so there's nowhere for the fumes and moisture to go except sit in the pipe once excess pressure has been released through the bov
with the re-circ...all that is going back into the system, air-flow is constant & so won't 'sit' in one place & accumulate

 

[_AJ_]

I think I had assumed that with the dumping of air via the VTA, the relative vacuum created in the piping after the turbo, would still draw fresh air through the induction side of the turbo (and passed the pipe and it's blanking plug), and as such, that particular location would never see any air containing oil fumes of any sort.

So you're saying that air from the rest of the induction loop will still pass back the wrong way through the impeller during closed throttle, but not with the recirc, mainly because the air (although containing oil fumes still presumeably?) shoots back through the bottom of the valve into the pipe, instead of into the engine bay?

 

[spn]

I suspect the oil is comming from the breather pipe which (assuming it's the same as a VI) joins to the turbo inlet pipe just upstream of where the blanking plug will be.

Probably nothing to worry about unless the build up is excessive.

The forge VTA valves come with a yellow spring fitted which is too weak and results in the valve opening on part throttle causing the rough running you described.

I ordered a spring kit from forge (£10 + post) over the phone (I don't think it's available on the website) and fitted the stiffest spring. The valve will now only opens on gear changes and is much more drivable.

I have got an HKS EIDS fitted to modify the AFM signal to cope with the loss of air - not sure how it would run without.


Cheers,


Simon

 

[_AJ_]

That's interesting. I've seen the spring kit on the Funky Product web site, which is where I got the dump valve from.

The thing is, it really hadn't been on for that long, and the inside of this blanking plug was pretty mucky. I'd cleaned it all off by the time it occured to me to take a picture of it.

I may get this spring and put it back on, just to see if it does it again.

 

[spn]

It might be down to the boost you're running raising the crank case pressure and causing more oil to be vented.

It's probably worth searching (or posting) on here to see what is normal at the boost you're running.

The stiffer spring should sort out the part throttle problems but won't necessarily fix the hesitation on gear change - worth a try though for the sake of £15 IMHO

Cheers,

Simon

 

[_AJ_]

Just ordered the spring kit. I'll put it back on then, and see if it developes this oily build up again in the blanking plug.

 

[Spanpody]

What air filter do you have fitted ?

The oil will be coming from the crankcase pipe which vents into the intake pipework as previously mentioned.

 

[Marvin]

Too strong a spring and it wont dump at all - all you will hear is the turbo compressor stalling - sounds fantastic chattering away until you realise it's not the dump valve and you are infact causing damage to your bearings

 

[_AJ_]

What air filter do you have fitted ?

Standard induction, standard element.

Also, thanks Span and spn.... I've just been looking around, and found the crankcase breather pipe... that does make sense judging by the 'splatter pattern' of the gunk. Can I assume that oil doesn't normally build up there because of the extra air flow provided by the recirc dump valve? In which case, over time, the Forge VTA item could produce quite a build up of this stuff!

The only thing that concerns me is that I can't find mention of this sort of thing anywhere else before. I don't like the idea of the turbo getting clogged up with all this stuff... having said that, VTA or no, it's still going through the turbo and the induction I guess.