Apexi Dump valve failure?

[leeroy_25]

Guy\'s I just had my motor rebuilt and now I have the car back and running in (although hardly pushing boost or rpm) I have noticed that I dont get my dump valve swoosh when I lift off. Instead I get turbo cheep!
My external wastegate has been plumbed differently from before as aparrently I had it connected to a blind nipple on the LIM! Doh! Fortunately I have been running it on spring pressure only anyway.
So I thought it might be that at first but I disconnected it and re-routed the dump valve and still the same.. I hae an Apexi Twin Chamber BOV by the way.
From what I can tell sucking on the vac line going to the dump vlave it is not holding suction. Even though only slightly I can continuously suck the pipe and the air seems to be escaping past the piston and in from the secondary chamber through the rubber pipe on the BOV. Is this a common failing on the apexi twin chamber BOV\'s? Any fix for it?
Strange that it was working perfect last time I drove the car before the rebuild?
Maybe when I can really load her up and pull higher revs it wil have enough suction to open the dump valve before the air has a chance to leak?! Main thing I want to know is am I doing any major harm to my turbo running it like this. I gather the sound is caused by the blades stalling in the back pressure of air created when the throttle closes. SO presumably this is putting excess load on the bearings?
Thoughts please.

Thank you
Lee

[m1tch]

Surely firstly you don\'t run boost when running in?

I would check for vac leaks and also the vac line you are using for the BOV, I found mine wasn\'t firing and I thought there was an issue with the bov, I found that the vac line was collapsing under boost then vacuum and was cutting the bov vacuum off before it got to the actual bov.

The cool sound you hear is the blades stalling, this will wreck the turbo bearings and might also wreck the compressor blades as well, the last owner of my car unplugged loads of vac lines and so the bov wasn\'t firing correctly, turbo needed a full rebuild due to the bearings being completly shot.

[leeroy_25]

Thanks Mitch. The line seems okay.. It\'s all new silicone. Or was done not long before the rebuild anyway.
I am not going on boost by choice. The turbo spools at like 2000rpm so I can\'t help getting a bit and when I am cruising I try and keep the boost completely off. It\'s not a full rebuild. Just rotor tips, corner seals and water seals. Rest was okay. Water seal went and I caught it straight away so didn\'t do any damage. Still sounds and feels like a completely different car even at low revs!

I\'ll try a new bit of hose jsut in case.. Do you think it\'s normal I could suck a little air through the BOV then? I.e it\'s not a perfectly sealed chamber? I opened it up expecting to see a diaphragm and I see it is just a metal piston with no sealing ring of any kind! Hence I would imagine it could never totally seal even if it was brand new?

As you point out it does sound very cool! But not worth knackering my turbo as that sounds cool too!

Cheers
Lee

[leeroy_25]

Fixed it!
After some more messing about it appears that if the dump valve it tee\'d off from another device like the wastegate or Boost controller it doesn\'t get enough vaccum to operate so I gave it it\'s own direct feed from the plenum and Bob\'s your uncle! it works again!.

Lee