1G BOV with two boost source nipples?

[TurboMike]

I gave my son my Spyder, he crashed and crushed the big sidemount intercooler. Couldnt find anyone still making or selling a used big sidemount, and we scored a used FMIC setup. The BOV on the pipes is a 1G but it has a second nipple drilled into the base of it with a cut off boost hose. I think I remember in the 90s before you could get good aftermarket BOVs people were drilling this second hole in a 1G bov but I cant remember why and what to run to this base nipple. If I had to guess the top nipple behind the diaphragm goes to the intake manifold so the BOV knows how to open like normal, but this new nipple that puts boost on the intercooler pipe side directly from the turbo the BOV can close again quicker? Thats my only guess. Anyone know so I can hook this thing up properly?

 

[Justin DuBois]

I gave my son my Spyder, he crashed and crushed the big sidemount intercooler. Couldnt find anyone still making or selling a used big sidemount, and we scored a used FMIC setup. The BOV on the pipes is a 1G but it has a second nipple drilled into the base of it with a cut off boost hose. I think I remember in the 90s before you could get good aftermarket BOVs people were drilling this second hole in a 1G bov but I cant remember why and what to run to this base nipple. If I had to guess the top nipple behind the diaphragm goes to the intake manifold so the BOV knows how to open like normal, but this new nipple that puts boost on the intercooler pipe side directly from the turbo the BOV can close again quicker? Thats my only guess. Anyone know so I can hook this thing up properly?

The Greddy Type S valves are setup like this with one on top of the diaphragm, and one on the bottom.

I think 1G's generally don't need this because there is an air channel internally supplied from the intake pipe that it is bolted onto to apply pressure to the bottom.

The idea is boost applied to both the top and bottom will negate each other, and the spring adjustment is used to overcome the pressure on the face of the valve plunger. If you plumb the top port to a boost/vac - it will hold the valve closed, and lift the valve open. The bottom port is plumbed to a "before throttle body" boost source, that does not see vacuum. This way any pressure differential created by a closing throttle plate will smoothly open the BOV, and reduce compressor surge.

 

[Talon43219]

It's probably has the "Dodge mod". I run a similar setup on my 2g. The mod allows you to run more boost pressure than a stock/crushed bov could before it would start to leak/bleed pressure.

 

[steve]

It's probably has the "Dodge mod". I run a similar setup on my 2g. The mod allows you to run more boost pressure than a stock/crushed bov could before it would start to leak/bleed pressure.

That's exactly what it was called. It's linked from the VFAQ site but here's the direct.

DDG- Talon BOV mod for HIGH BOOST

 

[Stapl3]

I've tested mine up to 80psi with out issue. I run 2 just for more volume. Otherwise they behave just like stock. Fantastic mod.

You have to follow the directions exactly for the desired result.

 

[TurboMike]

That's exactly what it was called. It's linked from the VFAQ site but here's the direct.

DDG- Talon BOV mod for HIGH BOOST

Wow, thanks! I assumed the top nipple went to intake manifold and couldnt understand why the bottom was needed if the before tbody boost was literally right under the BOV anyway. But now I know to run it from the turbo outlet.

 

[Justin DuBois]

Wow, thanks! I assumed the top nipple went to intake manifold and couldnt understand why the bottom was needed if the before tbody boost was literally right under the BOV anyway. But now I know to run it from the turbo outlet.

Where to tap a non vacuum boost source is a an individual choice - trial and error kind of thing. My setup is using a source on the throttle body, and I'm using the lightest spring pressure I can set on the Greddy. Others will use a pressure source at the turbo. I found a differential between the boost at the turbo and at the intake manifold, (make sense right - @throttle body air has already gone through the IC, where turbo outlet has not) and this was enough to open the BOV under WOT condition. I could have overcome this with a stronger spring setting, or I can use a different location - closer to the throttle body.

At the end of the day, you want to hold all the boost at WOT, and none of the boost as soon as you come off the gas.