Nightsilvia

ok, i have heard multiple things about bov placement and i have looked at previous threads on this topic but still have not found the answers i need. i have a greddy trust front mount intercooler on my SR and a turbo xs bov, the problem i have is the bov is not actuating. I do not have it directly on the main pipe, i dont have tools to cut and weld and am working on a tight budget. on the cold side of the intercooler piping there are two flanges, i have vacuum to the lower one and the bov on the larger, upper one. do I need to have it directly on the pipe or will the side flange work? also I have heard that bc it is MAF that i need to recirculate it back to the intake? i want to do it the safest way possible, with that said is it critical to have it recirculate? also would the placement of the bov be the reason it is not actuating? This is my first build I have done and just need some input from someone more experienced than myself.

Kingtal0n

1. You desire the bypass on the hot-side as close to the turbo as possible, for best longevity of that turbo, and quickest response (quickest pressure drop)

2. You can ONLY run the bypass open to the atmosphere IF it only vents when you are off-throttle and not at idle. There is a blow-off designed like that, the HKS SSQV. Now, understand that this is not an IDEAL setup, because it will still sometimes catch the maf and over-fuel the motor, and also, that blow-off is slow, so you will still surge some (bad for the turbo)

3. your ideal setup is a push-type bypass (blow-off) like the greddy type-S or HKS RACE on the hot side, recirculated to the post-maf pre-turbo intake pipe. The bypass should be set weakly such that it is open at idle. Dial the spring tension (adjustment) loose enough that you eliminate all audible surge at nearly all throttle positions.

other tips,
use a dedicated vacuum line/source. No T's.
If your bypass isn't working in the mean time, you can remove the wastegate arm from the wastegate "flapper" to eliminate the turbine (no more boost). This will allow you to drive the car as hard as you want, without surging the compressor and damaging the turbo.

l adam l

^^this guy seems to know his stuff

on my s14 sr20 i ran a HKS SSQV on the hotside and had a dedicated vacuum, never had any compressor surge.

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Nightsilvia

thanks a lot for the help!!

Marco,s14..

Bov its suppost to have vaccum and boost, that might be the reason why bov is not working.
And yes you do have to re-serculate bov, unless you have a tune.

S14DB

The Vacuum line needs to go on the other side of the throttle body on the intake manifold. The 2 lines you speak of, The larger one is for the IACV and the little one for the wastegate. The BOV will never operate with the vac line hooked up to the charge pipe. It uses the differential pressure behind the TB to open.

You will want to recirulate it between the MAF and turbo. Dumping air that has already gone through the MAF causes the engine to go rich as the ECU thinks the air is still going to the motor. At least it's wasted gas, worst case it bogs and stalls on you.
Most of the charge pressure is in the Intercooler. Having the BOV on the hot pipe causes the air to back flow to it. Causing some turbulence in the pipe and lag in between shifts. Nissan put the BOV on the cold pipe for a reason. Dumps the pressure from the intercooler downstream so the flow continues in the same direction.

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