Craigorypeck
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| posted on 31/10/11 at 11:08 PM |
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dumb recirc valve q
which way is it fitted...?
Pressure in at the bottom and vented to the right or the other way around so the vacuum does all the work..
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coyoteboy
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| posted on 31/10/11 at 11:13 PM |
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Normally bottom goes to boost on all AFAIK.
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MakeEverything
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| posted on 31/10/11 at 11:24 PM |
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quote:
Originally posted by coyoteboy
Normally bottom goes to boost on all AFAIK.
Correct. The boost pressure pushes up on the diaphragm which is also lifted by vacuum from the manifold to "Blow Off". If you fit it the
other way round it wont work.
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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Craigorypeck
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| posted on 31/10/11 at 11:30 PM |
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As i first thought then i started thinking! Hehe.. Doh!
Thanks
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flibble
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| posted on 31/10/11 at 11:38 PM |
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I'm going to have to disagree until I realise I'm wrong (wont take long!), bosst goes in the side and vents out the bottom, I first
thought it'd be the other way round but then boost pushes it open all the time, you only want the vac hose at the top to do the actuating.
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MakeEverything
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| posted on 31/10/11 at 11:45 PM |
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quote:
Originally posted by flibble
I'm going to have to disagree until I realise I'm wrong (wont take long!), bosst goes in the side and vents out the bottom, I first
thought it'd be the other way round but then boost pushes it open all the time, you only want the vac hose at the top to do the actuating.
Thats what happens to mine (Being a supercharger) however, the supercharger pushes out pressure constantly, whereas a turbo does not. These valves
work exactly the same way as an atmospheric BOV, except the blown off pressure is recycled back into the airbox or through an internal wastegate.
On full chat, mine closes and allows full boost pressure into the manifold. When the butterflies close, the negative pressure opens the valve. Idle
sees the valve bleed excess pressure because the butterflies arent open much.
[Edited on 31-10-11 by MakeEverything]
[Edited on 31-10-11 by MakeEverything]
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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MakeEverything
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| posted on 31/10/11 at 11:47 PM |
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quote:
Originally posted by flibble
I'm going to have to disagree until I realise I'm wrong (wont take long!), bosst goes in the side and vents out the bottom, I first
thought it'd be the other way round but then boost pushes it open all the time, you only want the vac hose at the top to do the actuating.
In fact, i wouldnt be surprised if running it your way would dislodge the piston and prevent it from sealing correctly.
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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flibble
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| posted on 31/10/11 at 11:51 PM |
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I'm going to have to go see tommorow what happens if I turn it round on the SAAB, it's been on the other way all year 
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MakeEverything
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| posted on 1/11/11 at 12:00 AM |
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quote:
Originally posted by flibble
I'm going to have to go see tommorow what happens if I turn it round on the SAAB, it's been on the other way all year
Id be interested to see the result actually.
ETA: Whilst youve got it off, have a look at the shape of the nylon piston which is what leads me to believe that i have it correct. I could be wrong
though for a supercharger you normally have a diverting valve rather than a BOV.
[Edited on 1-11-11 by MakeEverything]
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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flibble
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| posted on 1/11/11 at 12:09 AM |
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Been looking around on T'interweb and now I'm back to thinking I may be right, at least for the standard bosch recirc that SAAB's
come with.. >Like this< I'll try it the other way out of curiosity though
I seem to remember it was with a supercharger on my MX6 that it would't work properly with the boost to the bottom either, but then, I'm
wrong about a lot of things!
[Edited on 1-11-11 by flibble]
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Craigorypeck
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| posted on 1/11/11 at 12:25 AM |
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With boost in the bottom it would guard against a backfire through inlet..??
TBH I may just vent the outlet (which ever it is) to air for now as there aint much room for extra pipe work and sending hot air back to the charger
doesnt make much sense. . . .
Which is it!? 
Edit- inlet must be the bottom... cause why do they have different rate springs?? vacuum will be the same when butterflies are closed...? but more
boost requires a stiffer spring..
[Edited on 1/11/11 by Craigorypeck]
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MakeEverything
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| posted on 1/11/11 at 12:28 AM |
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This is mine, its not a recirc so that could be where were disagreeing.
 
Dump Valve in
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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coyoteboy
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| posted on 1/11/11 at 12:55 AM |
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I've stripped an atmos-venting one apart to modify it, the bottom is the boost connection. It has a small plunger diameter that seals into the
bottom hose. In the case of a supercharger that builds boost at idle it's a bit different, but in a turbo engine there's only boost with
the throttle open. The piston is biased via a spring so it's held shut and the small diameter plug presents force X to the piston. When the
throttle is opened the boost is present at the top AND the bottom and the top has a larger surface area, presenting 3-4x the force on the piston (or
diaphragm) - this holds it shut during boost and only actuates when the throttle is shut providing positive pressure to the small plunger and
"negative" to the larger side, holding it open. Providing boost to the side inlet won't do a lot, other than leak a bit during
boost. It'll still blow off but it'll leak too,
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Craigorypeck
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| posted on 1/11/11 at 01:24 AM |
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that makes sense.. thanks!
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Davey D
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| posted on 1/11/11 at 06:09 AM |
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every aftermarket dump valve ive seen (both dump to atm. and recirc) have been boost into the underside, and then recirc type dump out the side.
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Stott
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| posted on 1/11/11 at 06:50 AM |
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The Bosch type black plastic recirculate has flow direction printed on it, in at the bottom, out the side iirc.
Interestingly though they are installed backwards on vag 1.8t engines as standard, I found this on my octavia vrs and s3. They were plumbed in the
side, out the bottom.
[Edited on 1/11/11 by Stott]
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mark chandler
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| posted on 1/11/11 at 07:51 AM |
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Boost in the bottom so it acts against the spring, this is then preloaded so becomes very sensitive to vacumn and provides an overboost protection so
set the spring preload with shims a few PSI above maximum allowed boost so it will vent if all goes wrong or if for example the vacumn pipe becomes
disconnected or splits.
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flak monkey
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| posted on 1/11/11 at 07:58 AM |
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quote:
Originally posted by mark chandler
Boost in the bottom so it acts against the spring, this is then preloaded so becomes very sensitive to vacumn and provides an overboost protection so
set the spring preload with shims a few PSI above maximum allowed boost so it will vent if all goes wrong or if for example the vacumn pipe becomes
disconnected or splits.
What he said ^^^
Sera
http://www.motosera.com
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MikeRJ
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| posted on 1/11/11 at 08:27 AM |
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quote:
Originally posted by mark chandler
Boost in the bottom so it acts against the spring, this is then preloaded so becomes very sensitive to vacumn and provides an overboost protection so
set the spring preload with shims a few PSI above maximum allowed boost so it will vent if all goes wrong or if for example the vacumn pipe becomes
disconnected or splits.
That's the only circumstance under which it could provide protection. If the wastegate stuck or a boost controller failed it wouldn't
help.
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