Well there is a lot of controversy here.
I am a proponent of putting it near the compressor.
The throttle body argument:
When the throttle plate closes, the air’s velocity is moving through the intercooler towards the throttle body. If the BOV opens at the instant the throttle plate closes, the inertial load of the air will continue to carry the compressed air out of the BOV. When the throttle plate closes the air already has “forward” velocity and the car will experience improved throttle response as a result. However, this is detrimental to your turbo (i’ll explain more later)
The compressor outlet argument:
The key here, is damping and delay. One folly it seems that TB-ers note is “putting it by the compressor outlet will vent twice the amount of air. The compressed air in the intercooler and the air coming out of the turbo” Let’s expunge this right away because nothing different is happening regarding how much air is vented at either location. (to a degree… you’ll just have to take my word for it).
Now, that aside, back to damping.
A BOV is a device with, inherent to it’s design, it’s own momentum and inertia, in that it takes a split second to open after the throttle plate is closed. What happens in this split second between the operation of the two devices is the generation of a pressure wave. It’s hard to quantify, but it’s surprising how damaging and intense these waves can be. Now, these pressure waves are going to be generated regardless of where you place the BOV. Assuming that we can’t stop the formation these damaging waves, we need to destroy them or dispose of them.
When the BOV is located close the the throttle body, the pressure wave is created, but the wave still travels back through the rushing air. Just as if you were to put a compression wave into a slinky that’s in a moving car. This wave, despite the fact that it’s moving against the airstream will continue, unabated until it reaches the compressor wheel, disrupting it’s rotation.
Now let’s look at this scenario with the BOV place on the cold side. In this case, the air exiting the BOV is that of a converging airstream, in that it’s venting compressed air located in the IC and cold piping as well as the air still being forced from the turbo’s compressor. What’s happening here is a bit of turbulence at the convergence actually helps to kill the pressure wave. Also, since the pressure wave is part of the exiting air stream, it will tend to exit with the venting air. This all adds up to longer life for your expensive snail.
~ciao!
