Is this the right VSV? help needed...

[Mike B]

Hi Everyone,

 

Need your help......My new sup came from Japan (thanks Jurgen), and it's had a bit of work done to it over there..

 

This is not quite a standard intake system, and I think it's had some VSV surgery along the way, and unfortunately it's not running quite right...

 

The VSV for the intake air control valve seems to be the primary suspect at the moment. There is a naked terminal on the the VSV that when capped (it wasn't supplied to me capped) produced smooth boost at .4 bar right through the rev band, but no 2nd turbo power increase, or appreciable power from the 1st turbo either - but it is smooth and steady holding .4 of a bar.

 

When you un-cap this terminal boost on turbo 1 oscillates between .5bar and 0, cycling over and over until it hits 4k revs and hey presto full and smooth 2nd turbo power, just like normal.

 

Can someone who knows about these things tell me if it is the right VSV for the IACV and if so where the uncapped end (or general plumming if mine is completely misplummbed) goes to... I have no idea, it must go somewhere!

 

I'm really scratching my head and need your help!

[Ian C]

That barb you are plugging/unplugging is the vent from the VSV that allows it to dump whatever pressurised air it's got to atmosphere. It should have a tiny air filter on the size of a rolo.

 

When that VSV switches to the actuator, the actuator gets positive pressure and it opens the IACV and allows air from turbo #2 to join in the fun. When it switches off again, the pressurised air from the black hose in your picture gets blocked off, and the small bit of pressurised air stored in the actuator and the hose gets vented via the filter to the outside world - and so the IACV actuator shuts.

 

Now, if you were blocking it off, I'd say the IACV would stay open all the time and may cause the oscillations you describe by venting all of the first turbo's boost out via the non-rotating second one. However, you say you get the oscillations if it's *not* blocked, so let's look at that. Perhapst this VSV isn't doing it's job and is venting boost out the filter barb even when it should be directing it to the IACV. Either it's not switching or it's leaking.

 

Beyond this though, I think you may have other sequential system problems as well! It's possible that if this VSV is letting air through both ways regardless of it's intended switching state, when you cap the vent barb it in fact opens the IACV and dumps any boost #1 is making anyway, to a point where the IACV is acting like a wastegate, only on the intake side. That would explain the steady 0.4bar. Although I'd expect #2 to still come online... (ah, I've re-read your post and you say it does, interesting )

 

I'd say, step one, take the black hose off the VSV and block it up (bolt or fold and tietag), then go for a test - if this VSV is venting boost or causing the IACV to open prematurely, this will give you back #1 turbo's full boost. It's not a fix but it's the first diagnostic step.

 

If you do need one of these VSVs I think Heckler has a spare one

 

-Ian

[Mike B]

Thanks for that; I'll be back on the case tomorrow. Would love to say that I love a good mystery, but this one is starting to get more complicated the further I look...

 

Oh and what is stock pressure for the 1st turbo just for refrence? 0.6 bar?

 

The hose that I replaced with the new blue hose was so stiff it was almost solid. I have a feeling I may be replacing a lot of hoses soon. They don't last for ever I guess,

 

Although this is a 94 car, it's only done 72k km (43k miles).

 

thanks for the help - I may be back!!

[Mike B]

I'd say, step one, take the black hose off the VSV and block it up (bolt or fold and tietag), then go for a test - if this VSV is venting boost or causing the IACV to open prematurely, this will give you back #1 turbo's full boost. It's not a fix but it's the first diagnostic step.

 

If you do need one of these VSVs I think Heckler has a spare one

 

-Ian

 

Hi Ian, and everyone else.

 

Right; curiosity got the better of me and, as suggested, I plugged the feed to the IACV to test the first turbo, (preventing the IACV actuator from working) and guess what. Still get kangaroo boost on turbo 1. 0.4bar to 0.2 bar cycling over and over. I checked the IACV actuator and it seems free with good movement, strong spring return and the valve slides open to a point and then clicks back into place when released - all seems fine.

 

Now the next step can only be one of three possibilities;

 

It's either EGBV actuator or EGBV VSV malfuctioning and not providing steady realease when the system is starting to spool turbo 2. The only thing is that the kangaroo boost starts as soon as the first turbo starts to spool, say 2.2k rpm and it kangaroos from here upwards. Does the EGBV act as the only wastegate for turbo one?

 

Or it could be a similar malfuction on the main wastegate or wastegate vsv... but as far as I understand the wastegate only opens when you pass 4k rpm and both turbos are working in parralell...

 

Lastly it could be the HKS Fcon opening vsv's when it's not supposed to...

 

Still this doesn't answer the question as to why, when I block the vent on the IACV VSV I get steady, if pathetic 0.4 bar of first turbo boost with no second. It's getting more and more confusing!

 

I am thinking about disabling and plugging the EGBV vsv too see if then holds steady boost on turbo one. Obviously I would have to take it steady and keep under 3.5k. would this be the logical next step?

 

What is the standard operating pressure of turbo one and what are it's safe limits?

 

hope you can help!

[Mike B]

help me please!!!