Recirculating BOV Wanted

**Slider15** · 03-09-2012, 03:45 PM

Ok so i have a stock RB20 and i am guily of enjoying the louder sound of an aftermarket BOV. Ive been reading reading around the forum and i believe that a recirculating BOV is what i am going to go with. That being said, can you guys help with some suggestions on a moderately priced recirculating BOV?

**mfroese** · 03-09-2012, 04:36 PM

I've been looking at the GFB Repons BOV from Australia, has the recirc plumbing but also has a switch to make it an atmospheric when wanted.

http://www.gfb.com.au/products?page=...ategory_id=180

At the moment I've used the stock RB20 BOV and bent the spring chamber to allow a bit more pressure to build up before it starts to bleed off at the top end. Daily driving and in town got considerably more manageable after I removed my atmospheric and my stalling on stops went away if I didn't give it a shot of gas. Still pushes 16psi when I need it to.

**Skym** · 03-09-2012, 05:22 PM

Most BOV's including stock BOV are a diaphram type BOV and diaphram can get affected by heat, so can slow reaction time of BOV. Piston type BOV reacts faster than diaphram type BOV and releases built up pressure just below 0 on boost gauge when back off throttle that helps to keep turbo spooled up, which when get back on throttle it helps to improve offboost response / transient hp, torque, pickup (RB20DET needs this extra boost, as lacks torque, hp at lower rpm). Being a pull type BOV, can make engine increase in hp, torque due to boost pressure that keeps valve closed inside pull type BOV, which means BOV doesn't leak and more air gets to engine, leans out A/F ratio, increases hp, torque (Also I think is part of what increases transient hp, torque / response). Stock BOV is a push type BOV and valve gets pushed open and starts to leak, especially when over 10psi or so.

Piston, pull type BOV = Synapse BOV. I have a Synapse BOV on my car and those are the differences I noticed between stock BOV, modified stock BOV and Synapse BOV.

Here's a videoclip showing the hp, torque difference between a leaking push type stock BOV and a pull type Synapse BOV -

http://www.youtube.com/watch?v=oIAVLG2nh_U

Here's a videoclip showing the transient response / transient hp, torque, hp increases when comparing leaking BOV to a non leaking Synapse BOV -

http://www.youtube.com/watch?v=iPIa4HbPTAM

Some people say a BOV doesn't make much difference, but in reality it does with hp if it leaks, slow to react, etc.

**Slider15** · 03-09-2012, 09:55 PM

Anyone have any other suggestions?

**Slider15** · 03-09-2012, 09:56 PM

Skym, what are the prices like for the Synapse BOV's?

**Woodly** · 03-09-2012, 10:29 PM

I use this
http://www.frsport.com/Turbosmart-TS...n_p_27572.html

**Slider15** · 03-10-2012, 02:49 PM

Woodly, Do you like that BOV? Any stalling or sputtering issues?

**Woodly** · 03-10-2012, 04:21 PM

No issues on my rb25, I don't see why it would cause problems on a 20. You shouldn't get stalling or shutters unless it vents because the ecu takes it as losing air somewhere.

**Skym** · 03-10-2012, 07:39 PM

From what I understand, MAF measures amount of incoming air and ECU injects amount of fuel to match. When remove air from intake piping via a VTA (Vent To Atmosphere) BOV, ECU has no way to know air was removed, so engine gets less air and ECU still injects the same amount of fuel thus engine runs richer.

It's due to placement of MAF (infront of turbo or known as a draw through MAF setup). Recirculating air from BOV like factory does puts air back into intakepiping infront of turbo, through turbo, intakepiping after turbo, into engine, so engine gets the same amount of air and doesn't run rich. That's why recirculating BOV is best with a draw through MAF setup and why factory recirculate the air from stock BOV.

For bolting a log style Synapse BOV on RB20DET (recirculating air), you need -

Log style Synapse BOV
Mitsubishi Flange (stock BOV has a Mitsubishi logo on the side of it, so is made by Mitsubishi and has the same shape flange)
Synapse Boost Connect Kit (don't use anything else)
Samco brand 45 degree angle 1.25" silicon hose (or similar if you can find it locally)
2x worm drive intake hoseclamps for 1.25" hose.
6mm barb to 1/8 screw brass fitting (fit's into stock BOV 6mm ID vacuum hose and use screw in 1/8 fitting, Y fitting with Synapse vacuum hose from Synapse Boost Connect Kit inbetween those fittings, back of log style Synapse BOV)

Log style Synapse BOV -

http://synapseengineering.pinnacleca...alves-2-1.html

Fitting the flange is the hard part (need 2x people to do it properly, one to hold flange + log Synapse BOV together while other tightens screws), so I would use the other DV style Synapse BOV they sell if you can that has the clamp style flange which is alot easier, probably more reliable at higher boost levels.

This is the DV style Synapse BOV kit for RB20DET -

http://synapseengineering.pinnacleca...bo-646-16.html

I might switch to the DV style Synapse BOV kit later on, but the log style Synapse BOV hasn't failed in 2-3 years or so and functions the same way it did after it was installed (it has worked flawlessly so far). Also it doesn't need gaskets, as uses o rings on flange and can be rebuilt / serviced (can buy a rebuild kit).