I have had two different custom road race setups built by Full-Race for an ITR. I am now re-building it a third time to make it more reliable with a V-band on the turbo outlet. The first setup had the BOV located on the inlet (turbo) side of the intercooler, welded directly on the end tank. The second setup from them had the BOV located on the charge pipe about 12" from the throttle body. So obviously the guys at Full-Race do it more than one way. But which is better, as I am having difficultly seeing that one would be better than the other? There was some good BOV discussion here:

https://honda-tech.com/zerothread?id=1286873

and in a few other threads, but disccussions seemed un-conclusive as to whether it matters at all, is better close to the turbo or better close to the TB.

I am assuming when the throttle plate closes, the entire system from compressor outlet to intake manifold is at about the same pressure, being 1-2 psi higher at the compressor outlet, say 12 psi at turbo end and 10 psi at TB. When the TB closes, the air flow stops almost instantly and thus the air current stops, making the pressure everywhere the same as at the turbo end, around 12 psi, since there is no air flow and thus no pressure drop across any resistive element, similar to an electrical system with no current which must have the same voltage (pressure) everywhere as there are no voltage drops due to no current. Now a few engine rotations later, the pressure in the intake manifold drops as the engine's pistons pump the pressurized air out of the intake manifold and create a vacuum from the pistons to the TB plate. The pressure remaining in the charge pipe wants to continue building at 0 cfm so pressure spikes as it takes no time at all for compressor to build pressure with zero flow. Low turbin flow and pressure in charge system slows down compressor wheel and actually wants to go backwards and escape back up the inlet of the compressor which is at about 0 psi. This is bad for the compressor wheel as we go towards surge condition. So we use a BOV to release this static pressure. When it opens, the air rushes out from the entire charge pipe system very quiclky until the pressure there reaches atmospheric or 0 psi. The air has to flow backwards from the throttle plate end to get out through the BOV, and forwards from the turbo end to the zero pressure point at the open BOV.

So now we have vacuum on one side of the TB and a constant single pressure of 0 psi in the entire charge system from compressor wheel to the other side of the TB plate since all pressure was released when the BOV opened. When the TB opens, the engine vacuum in the IM of say -22 in w.g. wants to suck down the charge system while the compressor wheel wants to build it back up to 12 psi. This takes a while due to the turbo inertia and initial low exhaust flow, and the time to fill the charge end of the turbo, and thus we have lag.

So does it matter where we put the BOV? I tend to think it makes very little difference.