BOV

New Blow Off Valve (BOV)

Notes

Very easy install procedure, it took me approx 10 mins to complete.

Background

When you're boosted up and the throttle plate closes (shift or let off), the pressurized air mass in the intake system tries to push back against the turbo compressor wheel. The stock BOV's purpose is to evacuate this air mass when the throttle is closed, and 'feed' it back into the turbo inlet hose, thereby protecting the turbo from the shock of the reverse direction air hitting it when spooled up. An additional benefit of the air being fed in front of the turbo is that is keeps it spooling through the shift, reducing lag.

The stock BOV seems to have a very short life span, we have seen many cars under 100k miles with non-functional BOVs. After market BOVs set-ups with cool custom piping will cost over $200. This solution will resolve the problem for under $50.

To check your BOV, remove your stock BOV and blow through the main two 3/4" hoses. If you can breath straight through it, your BOV is broken and you will love the increased performance this replacement gives you. If your unit is functional, you will not be able to breath through the unit. I personally suggest replacing it anyway, it's too small for when you want to increase your boost pressures and flow rates at about Mod Stage III.

This SAAB BOV has been tested on dozens of SOGI members cars, it works just great.

Hear the sound of a functional BOV

Note, the extra sounds of my HKS intake and Hi-Flow exhaust system may sound different than your car, but listen to the pressure realease at the shift.

Skills needed

Parts ordering, screwdriver and hose cutting- phew!
: 1.5 ft. 1" inner diameter (ID) radiator hose.; 8" 5mm-6mm (ID) vaccum hose; 2 screw-type hose clamps: 'finger size'; 4 screw-type hose clamps: 3/4" - 2" range.

This is the new BOSCH BOV in place.

Procedure:

Remove the stock BOV

It's in the engine bay, above the turbo inlet hose.

There is a hose to the turbo inlet, one to the 3000 pipe, and one small hose to the 'front chrome intake pipe'.

Remove these three hoses, and their clamps.

SAVE the metal sleeve which acts as the hose-joiner to the turbo inlet.

Install new BOV

Cut the 1" radiator hose to make a 3" long section.

Place this hose on the bottom connection of the BOV.

Repeat to make a 5" long section.

Place this hose on the side connection of the BOV.

Place the 5mm-6mm hose on the top of the BOV.

Insert the metal sleeve on the bottom hose, put a clamp on it.

Since the sleeve is 3/4" and the hose is 1", wind that clamp down REAL GOOD!

Trim the hose which sticks out past the clamp, you want the sleeve to recess into the inlet hose well.

Make sure enough sleeve is exposed.

Place the BOV, bottom hose w/sleeve, on the turbo inlet.

Check that the side hose is 'level' with the 3000 pipe connection.

If not, trim the 1" bottom hose on the end that you do not have a clamp on yet.

Repeat until the side connection will be straight on. Now put the clamp on the bottom hose.

With the BOV mounted on the bottom connection, bend the side hose to the 3000 pipe sleeve.

If it's nice and level, clamp that interface down. Make sure the bend is gradual, and does not pinch off the airway.

If there is too much hose and it bends weird, shorten the hose.

Attach the other end of the 6mm hose to the intake pipe. Cut to adjust length if necc. and clamp both ends.

The clamp will not clear the head of the BOV well, do your best to secure the 6mm hose here.

Operation

Drive the car and boost up, and snap the throttle shut, notice the lack of flutter and smile.

Check your peak boost.

My BOV worked so well, I started to hit fuel cut from the added boost! (Was dialed in at 12psi.)

Note

The BOV will make a little 'whoo' sound when the vac/boost crosses or is sustained at 0psi.

This has been noted on the first two Supras using the SAAB BOV. It is not expected to be

a problem. I think it's the valve's diaphram oscilating. HEAR THE SOUND

Equipment needed

Compressor Overpressure Valve

Procedure:

Remove the stock BOV

Install new BOV

Operation

Note