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BOVs

Old 07-23-2008, 08:31 AM
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what makes one setup better than the other?
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Old 07-23-2008, 10:44 AM
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Are you asking about valve placement or valve size and design?

In theory it should be as close to the throttle plates as possible, in reality, I havent seen it make any difference. I like the valves with adjustable springs so you can dial in the blow off differential pressure, some valves like the Tial are built very well, but it takes a lot of messing with springs and clippers to get the spring rate right. I ended up with a transmission shift kit spring trimmed a few coils to make mine work with the lower vacuum of the bridgeport.

The greatest effect I have noticed, is when the signal source is tied in with other devices like fpr's, boost controllers that add volume at the end of small line, the added volume of the other devices and the chamber of the bov affect each other a little, the volume causes a change in pressure delay to all the devices on the line, and if the line between the FPR and the bov is shorter than between all and the manifold, the back pressure from the bov can make the fpr bounce. I like to keep all diaphragm devices seperate on their own lines. The stiffer the signal line, the more responsive it is as well, some of that cheap silicone hose swells under boost and collapses easily under vacuum, then splits, check the wall thickness and collapsability when you buy hose.
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Old 07-23-2008, 03:55 PM
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ive noticed that diaphram pheonomina too. bov needs to be seperate. boost guage and the map sensor seem like they are ok together though.
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Old 07-23-2008, 07:19 PM
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One thing to consider when thinking hot v. cold side is longevity. The BOV on the cold side obviously doesn't have to deal with as much heat!
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Old 07-23-2008, 11:13 PM
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Originally Posted by Maxt' post='905255' date='Jul 23 2008, 11:44 AM
Are you asking about valve placement or valve size and design?

In theory it should be as close to the throttle plates as possible, in reality, I havent seen it make any difference. I like the valves with adjustable springs so you can dial in the blow off differential pressure, some valves like the Tial are built very well, but it takes a lot of messing with springs and clippers to get the spring rate right. I ended up with a transmission shift kit spring trimmed a few coils to make mine work with the lower vacuum of the bridgeport.

The greatest effect I have noticed, is when the signal source is tied in with other devices like fpr's, boost controllers that add volume at the end of small line, the added volume of the other devices and the chamber of the bov affect each other a little, the volume causes a change in pressure delay to all the devices on the line, and if the line between the FPR and the bov is shorter than between all and the manifold, the back pressure from the bov can make the fpr bounce. I like to keep all diaphragm devices seperate on their own lines. The stiffer the signal line, the more responsive it is as well, some of that cheap silicone hose swells under boost and collapses easily under vacuum, then splits, check the wall thickness and collapsability when you buy hose.




A lot of race cars will run a vacuum/boost manifold. Each device has their own line, but they all pull from the same source. From the people that I have asked, everyone says that it has no ill effects when set up this way.



I'm like you and have always ran individual lines to each device and will use a high quality silicone hose. This next time around I'll be trying out the vacuum manifold setup.
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Old 07-24-2008, 05:40 PM
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Originally Posted by Comitatus' post='905291' date='Jul 23 2008, 09:13 PM
A lot of race cars will run a vacuum/boost manifold. Each device has their own line, but they all pull from the same source. From the people that I have asked, everyone says that it has no ill effects when set up this way.



I'm like you and have always ran individual lines to each device and will use a high quality silicone hose. This next time around I'll be trying out the vacuum manifold setup.


one of the nice things about doing a rotary, is that there are plenty of nipples to choose from!
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Old 08-17-2008, 04:42 PM
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ok i have a question. i just finished putting a s5 turbo engine into my 89 NA. i used a block off plate to remove the ACV and the air pump. i have a after market blow off valve (blitz is the brand its a whole kit with the tube) everything runs good except the BOV doesn't seem to be poping open at all. i currentley have the vacum line from the blow off valve run to pressure sensor on the right shock tower. IS THIS WRONG? were sould i run the vac line? or is this right and the BOV spring is to stiff?
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