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Discussion Starter #1
So I was thinking about getting an aftermarket BOV for my Supra...then I thought about how an auto trans works and realized it would probably be pointless. The only time you will hear it is when you release the gas pedal, since unlike a manual the throttle body doesn't close between shifts(unless power shifting). Sure it will purge anytime you let off the gas under boost but is there any point (other than sound) or advantage to adding an HKS BOV to an auto? From what I have heard the stock BOV is one of the best options out there.
 

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With my single turbo and turbo XS blow off you can hear it a little when the trac butterfly closes between shifts. For stock twins I would just leave the stock blow off it does it's job fine. And with aftermarket and the maf you run the problem of it getting rich every time you let off due to the air escaping.
 

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Im currently using the synchronic diverter valve and it does make a slight noise once in awhile, but I thought the noise is considered inefficient? there are different settings to make it react faster/slower if sound is what you are going for. It also recirculates so no problem with the MAF.
 

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I have an auto TT as well. I personally feel that the BOV is an essential part of the complete turbo system. It was put on there from the factory, so it must serve a purpose right? I would think that the stock BOV is fine for the stock car. Even at BPU levels, I feel that the stock BOV will start becoming overwhelmed even if some people feel its one of the best out there.

What I have seen done, and what I am planning on doing, is leaving the stock BOV in place, and running an HKS mounted to an intercooler pipe. What I have noticed riding in my friends car (also automatic) is that under lighter throttle releases, you hear the stock BOV. Under heavier boost/throttle applications, you hear the HKS or aftermarket BOV. Maybe BOTH will do what they do, but you will mainly hear the aftermarket. (HKS in this situation)

On different platforms such as the MR2 turbo for example, a lot of those owners feel that removing the BOV completely increases between-shift boost or throttle response. But at what potential price?
 

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The stock BOV is actually a bypass valve, the air it releases gets recycled. An aftermarket BOV vents to atmosphere, hence the louder noise. If you have the stock MAF, you're releasing air that the ECU thinks is in the system to atmosphere. This causes the car to run richer for a little bit whenever you let off the throttle. Unless you're running MAP, a BOV hurts more than it helps.
 

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Discussion Starter #6
Ok cool, so it sounds like you guys agree, supersekret has an interesting setup though, I never thought of adding a BOV to an IC pipe and leave the factory in place. I also agree that a BOV is essential, otherwise you will get compressor surge, right now I get pretty good turbo flutter at about 1400rpm, but flutter shouldnt hurt the turbos like a surge will.
 

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I'd removed the BOV on my stock JDM twins and ran them hard at 21-22psi on a regular basis with around 10k miles before the turbo's died. Throttle response had improved tremendously as did boost threshold. Keeping mind the stock turbo's died at 125k miles - it's hard to gauge whether it was the age, the constant abuse at 21-22psi or the removal of a BOV that killed the turbo.

I'm running my S366 without a BOV as well.

There are a lot of Skyline (R32, R33, R34) owners who do the same here in the UK and in Australia as well as Supra / MR2 owners. The general consensus is the stock bypass valve was to meet NVH levels consumers demanded.
 

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