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| Mac Winter 76XB351GS |
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Gday,
I will be running a centrifugal supercharger at around 8psi. I am after a BOV or bypass valve to suit. Does anyone know of a good one? I have found a Bosch unit but it looks like it is made of plastic and I have heard that it may leak boost. Cheers, Matt
_________________ 76XBGS, 383c, custom crow cam, 4V p&p heads, Isky SS Valve+springs, extractors, 2.5"twins, MSD Ignition, Edelbrock intake, Forged bottom end, Barry Grant 750DP, thermo, discs, toploader, Holley fuel pump, SUPERCHARGED! |
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| twr7cx |
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The Bosch ones are fine - they're what CAPA use. AFAIK they are also what come on the XR6T and Audis and some other cars too!
Benny said you got a Powerdyne unit. Go see him at work and get one of the little silver Monza ones - should be fine and decent price. |
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| Mac Winter 76XB351GS |
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Thanks mate. I went into see Benny today and we couldnt find anything but turbo BOVs. Im after a proper supercharger one as the belt driven powerdyne doesnt like the pulsation of a turbo BOV. I'll just pick up one of the bosch units, wont be running that much through it anyway.
_________________ 76XBGS, 383c, custom crow cam, 4V p&p heads, Isky SS Valve+springs, extractors, 2.5"twins, MSD Ignition, Edelbrock intake, Forged bottom end, Barry Grant 750DP, thermo, discs, toploader, Holley fuel pump, SUPERCHARGED! |
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| twr7cx |
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Mac Winter 76XB351GS wrote: Thanks mate. I went into see Benny today and we couldnt find anything but turbo BOVs. Im after a proper supercharger one as the belt driven powerdyne doesnt like the pulsation of a turbo BOV. I'll just pick up one of the bosch units, wont be running that much through it anyway.
I'm pretty sure there's no difference. Think about it - a BOV is just a vent wtih a spring holding it closed. The boost pushes it up and the pressure escapes, when there's no more pressure to hold it open it s**t. The Bosch ones that Capa send with there kits are identical as I said above to that factory fitted to many turbo cars - so Capa and the car manufacturers don't see a difference between them either... As said above, try one of the little silver Monza units - about the same price as a Bosch one, but the body is mental so they look nicer... |
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| Mac Winter 76XB351GS |
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I was under the impression that a turbo BOV was designed to "flutter" keep some backpressure on the impeller, where as a supercharger one was designed to stay open untill the excess pressure is released.
I have heard that any "flutter" will give the internal belt a thrashing and kill it fairly quick.
_________________ 76XBGS, 383c, custom crow cam, 4V p&p heads, Isky SS Valve+springs, extractors, 2.5"twins, MSD Ignition, Edelbrock intake, Forged bottom end, Barry Grant 750DP, thermo, discs, toploader, Holley fuel pump, SUPERCHARGED! |
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| twr7cx |
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Mac Winter 76XB351GS wrote: I have heard that any "flutter" will give the internal belt a thrashing and kill it fairly quick.
Internal belt? As in inside the supercharger? Powerdynes are geared inside. I've never heard of two different kinds of BOV and couldn't find anything about that on the net. As I said above BOVs are very simple, just a spring holding a peice in place really... |
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| ltd351T |
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well you have bypass valves and Blow off valves, they are very similar but do different things, typically you'd use a bypass valve with a blower, so that it will vent the presure at idle taking the load off the blower.
the bosch BOV's have three different types. you will need at least 2 of them. |
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| xcabbi |
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bypass valves are only for positive displacement blowers that run as suck through throttle setups such as the eaton M series blowers.
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| twr7cx |
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My bad they are belt driven internally.
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| ltd351T |
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xcabbi wrote: bypass valves are only for positive displacement blowers that run as suck through throttle setups such as the eaton M series blowers.
centri like vortech, paxton, etc, they will benefit from bypass also. |
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| xcabbi |
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I can't quite see how as even if the throttle was open at idle they would still not be making any boost, not like a pd blower.
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| Slick |
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They'll make booost regardless! under driven? then bugger all! overdriven? watch out!!!
But nothing to sing & dance about!
_________________ Mind f**k!!! it works on feeble minded ignorant sheeples... there's plenty of em on this site... some are very intelligent but by god they are so thick!!! Pakrat wrote: You can buy them seppertly
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| 4.9 EF Futura |
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xcabbi wrote: I can't quite see how as even if the throttle was open at idle they would still not be making any boost, not like a pd blower.
The centrifugals prob dont flow enough to make boost at idle, but they move enough air to cause dramas lol. At idle on my old setup, you would have a steady flow of air being vented at idle. For s**t and giggles, i put my hand over the bypass vent, the RPM dropped... engine spluttered and sounded like a bucket of s**t... it never stalled tho... Even a slight kink in the hose i ran from the valve to its venting area near my front bumper would make the engine idle like s**t. Having said this, ive seen setups with no bypass... which makes me think you can prob tune your way out of it.
_________________ I promise..... I will never die. |
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| xcabbi |
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How was the bypass routed in your car Mart? I'm just trying to get a visual picture of a schematic so I can work out the logic behind it all.
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| ltd351T |
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blower is pumping air, if t/b is shut there is nowhere for it to go, although it might not register as "boost" it is a lot of volume, loading up the blower at idle, you'd be surprised how much air it actually is, bypass helps cool the blower also, by reducing load, and allowing circulation of fresh air.
sure you can tune around it or whatever, but it will always work better with a decent bypass, FYI a vortech V2 s trim on 351C, will bypass a huge ammount of air, even at light cruise, two bosch bypass isnt enough really, thats why all the blower oriented bypass valves are quite large. |
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