I'd always prided myself on not adding wank factor products to my Sil, but alas, I am just another 'rice boy' at heart. For a bit of fun, expensive fun I might add, I purchased a GFB Hybrid Blow Off Valve (BOV) from ModYourCar, so I could have the pssschtt that you either love or hate.

The Hybrid is a bit different to the normal BOVs as it has 2 outlets for the boosted air. One of the outlets is fitted with a trumpet to make as much noise as possible, while the other side has a fitting which allows a pipe to be fitted and returns to the air intake, after the air flow meter. This is supposed to help cars that are prone to backfiring with standard BOVs, by returning some of the filtered air. It also means the pssschtt sound is a bit quieter than other BOVs. Of course, you can do what I have done and have both outlets venting to atmosphere.

Blow Off Valve Location

There is some debate as to where the BOV should be located along the inlet pipework. Some say it should be right next to the throttle body, while others say it should be near the turbo. I guess I can see the arguments from both sides, but the way I see it, there is 7+psi of pressurised air in the pipes and that air is going to take the easiest route out, and when the throttle is closed that route should be through the BOV, whether it is near the throttle body or near the turbo. I actually think it would be better on the turbo side as it would be ejecting air that hasn't been cooled by the intercooler, but I'm no scientist.

Now mine is mounted close to the turbo, not for any reason other than it is a nice easy place to fit it. Its not the most stealth place to fit it, but it is easy to remove and return to stock should the need arise. The pipe the BOV is mounted on is a direct replacement of the original pipe that was in that location. As my BOV has the fitting to recirculate the air to the air intake this location is very handy, as it sits right near the intake fitting. All that's required is a short 1" (I think) hose and Bob's your Aunty.

Vacuum Lines

When I first fitted my BOV, I mistakenly used the small vacuum hose that went to the top of the charcoal canister. Not sure why, but this didn't allow my BOV to operate. All I got was a loud flutter from the pod filter, which I thought was the BOV working. With help from Terry, the BOV vacuum hose was spliced in to use the small hose that comes from the inlet manifold over to the 'whatsit' mounted on the shock tower.

Blow Off Valve and Electronic Boost Control Vacuum Lines

I received an email asking for an idea of how the boost control solenoid and blow off valve vacuum lines are hooked up on my Silvia. So it seemed like a good idea to add some pics to this incomplete article. I have colour coded the hoses and added notes to the pics. Green = BOV, Blue = EBC in, Purple = EBC out. Please excuse the state of the engine bay...

Note to self : Clean the d@mn engine bay

Drivers Side

Blue vacuum line from inlet manifold, across fan shroud to Charcoal Canister.
Green line from inlet manifold, tees to my boost gauge (clear tube), then tees to fuel pressure regulator. Crosses fan shroud to the other side of the engine bay.

Passengers Side

Note the Red 'vacuum' line. I initially used this on my BOV, but it didn't seem to work. It runs across the fan shroud to underneath the cold side intercooler pipe.
Blue line tees off to the Boost Control Solenoid and the Charcoal Canister.
Green line goes to a tee underneath the intercooler pipe. One side to BOV and the other to the green emissions control valve (I believe its called that).

Passengers Side

Blue line ends at the EBC.
Green line comes from tee, around air filter and to the BOV. The other tee you see is for my cruise control.
Purple line goes from EBC to tee junction. See next pic.

Passengers Side

Green line ends at the green emissions control thinghy.
Purple line from EBC ends at tee junction. Left side to wastegate, and the other to something I don't know the name of. This tee junction is already there, so you don't unplug anything.

Warning : This is just how my car is set up and even though it seems to work, please confirm with your favourite mechanic that you have set yours up correctly.

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