External blow off valve install

[halfjap1980]

Hey guys,

Ok, I miss the sound of the blow off valve from my RX-7 and want to get one for my GTR. I'm not familiar with the ins and outs of a twin turbo setup. I know there are 2 wastegates, but are there 2 BOV's? I'd imagine that they are recirculators. I already have an AM FMIC so install should be fairly easy. Other than that and a full AM exhaust, the rest of my setup is stock. Has anyone had any issues with lumpy idle with the stock BOV removed and an external BOV installed??

Sorry if there are some noobie questions in here, and thanks in advance for the help!

-Kenji

[Skym]

2x BOV behind front bumper on drivers side.

With MAF sensor (like factory car), recirculate BOV's. With MAP sensor (aftermarket ECU), BOV can recirculate or vent to atmosphere. Recirculating BOV gives best response.

Stock BOV is push type (leaks under boost and provides overboost protection when spring is overcome and valve opens at 10psi+). Some aftermarket BOV's like Synchronic BOV are pull type (don't leak under boost) and get hp gains throughout revrange.

[krarks]

I don't know if all GTR stock recircs leak though. I run 1 Bar which is well over 10PSI and no leaks...maybe it has to be higher than 1 bar for them to give in?

[Skym]

As far as I know, but can't 100% confirm that GTR has stronger springs in stock BOV's. I was talking about stock GTS BOV.

You can modify stock BOV by blocking off the boost feed hole and drilling hole in side of BOV to vent the air behind screw. This way stock BOV doesn't leak at 10psi+, but creates a flutter sound (form of compressor surge that is not good for turbo CHRA) at lower boost levels (0-5psi).

But I've found a good BOV like Synchronic BOV provides smoother off boost performance (I suspected a leaking BOV flange gasket that probably made engine accelerate rougher) and engine reacts straight away (no bog / hesitation like with modified stock BOV). Also gets to 0 on boost gauge very quickly. Like for example, when off boost, back off throttle. Then get back onto throttle, the response is so much faster with Synchronic BOV (nearly instant response) and gets back into boost.