[quote author=Brian_MDB link=board=boost;num=1112345970;start=15#20 date=05/06/05 at 00:18:17] jolly well mind getting back under there and disconnecting it [/quote]<br><br>I see the US contingent are learning some proper English. Will it be, "Cor blimey guvnor!" Next? Having said that, I don't know what; "whupping" means ;D.<br><br>With the vacuum hose disconnected, the piston will be sucked shut under rapid throttle openings, and it it will be assisted by the spring in staying shut. When the boost comes on, the pressure will push open the piston against the spring, wasting the pressure to air as there will be no balancing pressure from the plenum side.<br><br>What you are striving to acheive (I think) is a mechanism to allow the free passage of ambient air to the plenum under high vacuum situations without the inherent drag of the intake tract, including the turbo. You then want it to close as boost pressure is developed. The end result would be the quick throttle response of an N/A, with the boost of a turbo as the revs and time increase. Is that right?<br><br>If that is right then so far I'm not confused.....

<br><br>If the above is right, then I would imagine the flow required to make a difference would be large, i.e. a large, rapidly responding volume of fresh air. This would probably be best acheived by a reed valve as mentioned above, acting in a large pipe from the filtered side of the airbox to the intake plenum. The BOV/Dump valve (whatever you call it) function would still be required as this has to open when there is pressure in the intake tract, but unwanted pressure.<br><br>So, your idea is to combine the functions of the two as a recirculating dump valve is the same kind of hardware as the reed valve set-up I mention above? Well I think it is a good one. All it needs to do is:<br><br>Pressure in plenum << intake tract: Open valve<br>Pressure in plenum ~= or > intake tract: Close valve<br><br>I'm starting to confuse myself now about which bits are more or less pressure than anywhere else, but I'm wondering if it would be most effective having the breathing part engine-side of the throttle butterfly and the dump valve part on the intake side. I'm sure this would mess up loads of things though, not to mention the brake servo!<br><br>Now confused [smiley=damaged.gif]<br><br>Candles.