BOV Placement

[480sx]

This question poped out of a noob thread, and i dont think it will get as much attention as it deserves. Heres whats been said so far, anyone else have any ideas on it?

Um, you can mount it anywhere as long as you have the flange. The best place might be as close to the throttle body as possible.

Actually you wana mount a bov as close to the turbo as possible. Honestly it doesnt mater that much, but the idea behind a BOV is to prevent compressor surge. So naturally you want to vent the air closest to the turbo first, so theres no chance of any compressed air finding its way back through the compressor.

When you mount it near the throttle body, it normally would be considered the best spot. When the throttle body shuts, air starts to build up at that one area and compress its way back to the turbocharger itself. A bov near the throttle body would relieve pressure at the source. If it is mounted close to the turbocharger, you can count on some compressor surge.

That makes no sense tho... why mount it close to the throttle body? Think about it, when you close the throttle body the air that didn't get in and between the BOV and throttle body will be released through BOV.. what about all the air in the intercooler and in on the hot side? wheres that air going to exit out? Thats right, right back into the turbo.. I feel the best spot for a BOV is on the hot pipe itself. Perferably right in the middle of the hot pipe.

Sorry for such a long thread, just wanted to cover everything. Basicaly if you didnt feel like reading all of that, the question is as follows :Where is the best place to mount a Bov, and why?

[boznuttz]

C wik's post pwns all, lol. Check the other thread.

[480sx]

Yea lol i see that, for anyone searching however i got the money title, im just gona do this....

A BOV's job is to allow the turbo to flow enough air while maintaining some level of pressure so the turbo doesn't see surge. Any location between the TB and the turbo will relieve surge just fine. In many cases BOV mounting may be limited by available space. But my speculation is thast mounting it closer to the turbo has more advantages.

First, in a typical intercooled turbo set-up, there is a pressure drop across the intercooler. So a BOV mounted on the hot pipe will see greater pressure in the pipes (the actual amount will vary with intercooler design), which means for a given BOV opening event (lift and duration) it can flow more air. While the reality is that any properly sized BOV for a given turbo system should not have any problems flowing enough air, being able to flow more air on the onset of a pressure spike can reduce the peak pressure seen at the spike. If you mount it close to the throttle body, if there is a high pressure spike, the BOV needs to remove the excess pressure from right at the compressor exit moving air all the way through the rest of the plumbing. The response of the BOV where it matters most (at the compressor) is a little higher.

Second, A hot pipe mounted BOV will reduce some of the heat load placed on the intercooler. Intercoolers aren't typically able to exhcange heat at a constat rate with the ambient air. Instead, intercoolers are typically designed with some extra mass in it's walls so that it can store heat from the charge air even if it can't exhange heat as quickly with the ambient. Typical driving, even on race tracks have many occassions(braking and most turns) where you are not introducing more heat to the I/C, but the movement of the car is still allowing the I/C to transfer heat to ambient air. This could result in small improvements in the long run for performance, as I/C's will absorb more heat when they are cooler. This effect is particularly true with vented BOV's.

But as I stated already, any location will suffice for all intended purposes. The differences will be small and negligible. I wouldn't stress yourself too much with these details as in many cases, finding a place to mount it can be enough work already.

[boznuttz]

[spooled240]

When I had my bov located on the cold pipe near the tb, it made this weird chattering noise. When I switched to a blow-through setup, and relocated my bov on the hot pipe about 6 in. from the turbo, it sounded way better and I think it's relieving more air. I'm not exactly sure how, but my bov seems to working 10x better...