BOV Placement
 

Just thinking out loud here.

I know that almost every turbo kit I have ever seen has had the BOV as close to the TB as possible. Is there a reason for this? Or just for the easiness of the vacuum line plumbing?

The point of a BOV is to protect your turbo from compressor surge, so wouldn't it be best to put it as close to the turbo?

Or does it just not make a difference?

Thanks for listening. lol

It's easier to mount it close to the throttle body, but it's better to be close to the turbo (EFR does this)

Honestly, for most street cars, I don't really think it matters.

But I will run TWO blow off valves, FukIn' Mad TyTE JDMZ!!!!

there is a very nice thread about this!!
I hope you searched.

Here:

https://www.miataturbo.net/diy-turbo-discussion-14/bov-location-intake-manifold-34268/

That's a gimme. Next time, search.

Actually this is incorrect, it is better to mount the BOV on the cold side piping from everything I have read.

TurboXS reccomends them closer to the TB. I feel the reason is this.

Lets pretend this is the turbo-IC-TB air flow:

X------------IC------------BOV------TB

Now, when the BOV opens air will go like this:

X-----------IC-------------++ BOV ....TB (the +'s are air vented, the ... is non pressurized air)

What that does is keep all that air before the BOV still fairly pressurized.

Now, watch this:

X------BOV-----IC-------------------TB

vented:

X---++BOV++---IC----------------TB

Now, its venting at the BOV leaving air already passed the BOV semi pressurized (though I understand if you vent it anywhere its all going to eventually depressurize) that may create more of a bog in the system.

Also, it seems to me, the people having trouble running BOV's have been on the hot side, not the cold.

food for thought.

and a qoute...
"I'm sure you know the reasons for having a BOV/CBV, and the time when you need it is between shifts or on deceleration. On deceleration it doesn't matter diddly-squat where you put it, because you're going to lose all the pressure the turbo has built up.
But between shifts you want as little pressure lost as possible. Remeber, the IC has a large volume, which has to be pressurized before the TB. If you relieve pressure momentarily BEFORE the IC, you're going to spend more time filling back up that "pocket" of depressurized air because the IC is goiong exaggerate the pocket. If you relieve the pressure momentarily AFTER the IC, the IC is already pressurized, and the small pocket of air is going to be filled back up more quickly, since you're not needing to spend time filling the IC again. This equates to quicker pressure build between shifts."


EDIT: EFR is a self contained unit so it really shouldn't be mentioned rather then a BOV it's more of a bypass value.

:inout:

The only real reason why putting the bov post intercooler is more common is that with a "push" type bov (charge pipe pressure tries to push the bov open) you want to minimize the pressure differential betweeen the charge pipe side and the vacuum side.

Putting the bov before the intercooler will mean that there is a 1.5ish Psi pressure differential which can overcome The combined manifold and spring pressures causing a boost leak. Putting the valve after the intercooler allows for less valve springrate which improves bov response.

Of course none of this matters if you use a pull type bov which will open anytime there is vacuum in the system and will not open regardless of boost pressure.

Nope.

Its there to replace an annoying noise with a different annoying noise. Thats it.

Cool story, bro. Call me sometime :laugh:

I've ran the tb right next to the tb and i've ran it on top of my ic literally 2 damn feet away from the tb... I am hearing some kickback on top of the IC that i didnt hear when it was near the tb in other words TB > rest.

The EFR places its internal bov close to the compressor wheel because thats the optimal place to save the compressor from compressor surge. The point of a bov is to save your compressor from compressor surge, and if you think about it no matter where it is, the same amount of pressure will have to be built back up. During shifting, your bov only opens for a split second, you want the pressure to be released from as close to your compressor wheel as possible during that time. My old setup had my bov on the cold side, and i heard compressor surge frequently.

Oh yah? Why is that?

You do know that a pressure wave travels from the tb back to the turbo right? Correction your bov is open for any time you're in vac...


What is hot time? Hot side? If so you're trying to eliminate it, not hear it frequently.

I need to fix my original post. I meant my bov was on my COLD side, when i was getting compressor surge.

Now to your wave theory. First of all, its more of a pulse than a wave. A wave keeps going where its heading until it stops, a pulse will take the easy way out. Id rather have the wave exit out my bov right at my turbo, instead of a lesser "wave" heading back towards my turbo.

Closest to turbo is where it should be, if the bov is able to stand up to the heat.

Then your bov wasnt setup right. I have 0 compressor surge.
Pulse is a type of wave with only 1 peak... No magic here. One isnt smarter than the other to find a way out.

That pulse isnt going to look to make a 90 degree angle to fly out of your pipe. Its going to head right back to the turbo. The bov needs to be setup and open enough to allow the air to continue moving so the pulse never happens in the first place.

I'm glad you brought up the internal EFR turbos because that works a little differently than your average joe external vent to atmosphere bov. The internal bov is setup to open directly in front of the compressor wheel. That is the lowest pressure in the entire system. On the other side is high pressure. In other words the internal bov is setup to pull and lead that pulse out from the high pressure side.

I've had them a foot from the TB, 2 feet from the TB, and even welded directly onto my intercooler.

Never noticed one single bit of difference.

Mine works good. No IC.

I want to thank everyone for their opinions and input.

Say the BOV is right next to the TB, when it releases pressure during shifting, does the IC and hot side charge piping stay somewhat charged because the turbo is still spinning? or does it deplete the air quick enough to lose all pressure?

I'm looking to build boost the fastest without severe damage to the turbo(as in running no BOV). So if the BOV is closest to the turbo, would the charge pipe down stream of the BOV stay pressurized then?

Again, just thinking out loud. Trying to wrap my head around all this foreign stuff.

-David

(Posting from my phone.)

No all pressure is released it doesn't matter where on the pipe.

Thanks Brain!