blow off valve on supercharged motor
#1
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When i run my boat at 3500-4000 rpm's,i don't need to open throttle far enough to actually see any boost at manifold but when i mount a test gauge i actually have 7-10 psi backing up behind throttle body. I feel this extra load creates heat in the supercharger,puts stress on the belt and robs part throttle horse power turning the blower with no where for the air to go. My question is when procharger and all the other centrifugal supercharger companys make blower kits for cars/trucks they always incorporate a blow-off valve that bleeds off the boost until your manifold vacuum hits zero then it closes off but on their marine kits i don't see this being used. I figure that most boats are farther into the throttle and able to actually use all the boost at part throttle when using a smaller base engine. Is anyone using a blowoff valve with a centrifugal supercharger on here? Just curious,i spend alot of time cruising at part throttle and am looking for every possible variable to be correct. The other thing is but this doesn't hapen often is if I'm waay into the boost and you have to throttle back quickly i hear the blower huff and almost try to stall as the air its pumping has no where to go,Smitty
#2
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I believe the reason for no blow off valves is a Coast Guard regulated type of thing. If it backfired it could blow fire out the valve etc. Just a guess. I run Whipples and it does have a valve for lower rpm/boost condtions that recycles the air that is not getting used at cruise speeds. It vents the excess back to the output side of the blower and helps keep a constant smooth idle with no surging. If you search around you may find something that someone has made or whatever that will accomplish what you are asking for. Maybe you could make it work similarly to what is on the Whipples.
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Last edited by Smitty; 08-20-2005 at 05:21 PM.
#3
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The coasties don't like backfire valves in closed compartment boats.
#4
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Originally Posted by Cord
The coasties don't like backfire valves in closed compartment boats.
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my Vortech supercharger has a place for the back pressure valve but it has a plate bolted over it. If you look at the picture of mine it looks like you could use that same tube in between your blower and you intercooler and use the back pressure valve. You could call Vortech and see if they would sell you one?
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You are describing two different situations. One where you have boost between the S/C and the throttle plate at small throttle opening and the other is when you are at WOT and close the throttle and boost builds up behind the closed throttle and the S/C and boost/air will bacu up against the S/C and actually push the impeller which could hit the housing and break and at less just cause a reverberation noise and try and stop the impeller and be why you have belt dust. You can use the Vortech blowoff/popoff valve and vent it back to the aircleaner. The valve has ports on it to make it open under high vacuum in the manifold and high boost before the throttle. It can be done.
#7
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Originally Posted by cobra marty
You are describing two different situations. One where you have boost between the S/C and the throttle plate at small throttle opening and the other is when you are at WOT and close the throttle and boost builds up behind the closed throttle and the S/C and boost/air will bacu up against the S/C and actually push the impeller which could hit the housing and break and at less just cause a reverberation noise and try and stop the impeller and be why you have belt dust. You can use the Vortech blowoff/popoff valve and vent it back to the aircleaner. The valve has ports on it to make it open under high vacuum in the manifold and high boost before the throttle. It can be done.
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Look at their website for the Mondo blowoff valve. http://www.vortechsuperchargers.com/...s/aircomp.html