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 Post subject: Dump Valve
PostPosted: Tue Nov 24, 2009 9:57 am 
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Joined: Thu Oct 29, 2009 2:43 pm
Posts: 12
Location: UK
Car Model: None
Fitted a dump valve to my st165, and now seems to idle badly!

I have run the vacuum hose from the top of the dump valve to the nipple on the inlet manifold and the car seems to cut out due to the bad idle. when i dissconnect the vac hose it runs as normal, but then theres no dump valve function


halp! :?


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 Post subject:
PostPosted: Tue Nov 24, 2009 10:04 am 
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Joined: Thu Jul 14, 2005 12:44 pm
Posts: 4067
Location: drinking devil fuel
Car Model: ST205
It sounds like the idle valve os dumping even when it's idling. This is a common issue with AFM based cars :(

If the valve is adjustable you can try cranking up spring pressure to hold the valve shut. Also have a good nose aboit on www.gtfours.co.uk. There's a lot of how tos on there, moght just be one on fitting a dump valve to a 165. Kris and Loosey, the owners of that site are here too so may be able to offer more advise


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 Post subject:
PostPosted: Tue Nov 24, 2009 7:59 pm 
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Joined: Sun Nov 27, 2005 8:43 pm
Posts: 998
Location: NLD
Car Model: None
Try recirculating it back into the intake (after AFM, before turbo). It's a bit of hit and miss with the AFM as 205 said.

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 Post subject:
PostPosted: Tue Nov 24, 2009 9:05 pm 
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Joined: Sat Sep 02, 2006 3:13 pm
Posts: 3679
Location: Bournemouth
Car Model: None
Many dump valves open a bit on idle, so air goes in through that as well as the AFM, giving a false airflow reading and messing up the fueling.

As said, try tightening the spring pressure so it doesn't open at idle, although this will reduce the dump when needed.

Alternatives are to recirculate the DV outlet back to the intake on the turbo side of the AFM (will lose the sound) or try another DV type. (not sure which ones stay closed at idle)

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 Post subject:
PostPosted: Sun Dec 13, 2009 1:21 pm 
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Joined: Wed Oct 05, 2005 4:12 pm
Posts: 378
Location: Waterlooville, Hants
Car Model: ST185 CS/RC
A recirc would certainly do the job to cure the problem.

As far as getting adjustable ones goes, I have a Blitz SSBOV with an adjuster. Would it up a bit and tried it without the vacuum pipe attached - managed to run up to 0.5 bar before it forced the spring open - so yes, there's dump valves out there that stay shut at idle.

Hang on a mo though, just thought that the vacuum pipe will act against the spring when off boost, so it's not so clear cut. Don't know if there's sufficient vacuum at idle to overcome a 0.5 bar spring :?

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