New BOV location
 

I'm about to get my IC pipes welded up by my friend, now the question is should I place the BOV flange on the cold side before the TB like I used to have it? Or Weld it on the hot side near the turbo? I'm not re-sirculating the air so it's the hot side option pointless?

you'll want it as close to the throtte body as posible

This is a very debatable subject....I say put it where ever is most convenient. Mine is about a foot from the compressor outlet....whether its right or not is subjective...

+1 close to the throttle body.

both sides have advantages, but I say where its easiest to install.

As I understand it, which may or may not be accurate, you want it close to the TB. Something about the air having to change direction in the pipes, which makes sense.

This.

Pressure is pressure. The time difference in reducing it at the TB or the compressor housing from a 'cold-side' to 'hot-side' placement is miniscule and insignificant unlkess you have such a large volume at such high density that the BOV is not large enough to really effectively release it. I doubt anybody here is anywhere near that point.

So put it out of the way. If it were me, with most of the setups I have seen, near the IC outlet would be a great bet.

Hey are both easy to do, I just didn't know if one was a better spot than the other and different advantages

Since this was in a Honday fail thread....

My car was setup before I purchased with the BOV down in the fender on the passengers side on the cold side. What are the chances of a HKS SSQV bov sucking in dirt down there.... Small animals? ;)

BTW I prefer the "near TB" idea due to reversion on the TB side. Keep things moving.

+1 on close to the TB.

I dont see how. Any time it is open it's got positive pressure. As long as it is not in the direct path of debris I think it would be fine. I do remember that pic of the Honda though, from what I could see there that thing would get nailed by anything on the road the car went over. Ouch.

If we really want to get nitty-gritty, some pics of the IC and planned tubing paths would be good.

wrong.

If the BOV is doing its job well, it is opened/cracked whenever there is manifold vacuum. So thats at idle, cruising, and deceleration.
There are plenty of times where you can actually suck air in through the BOV, hence why some people run filters on the outlets of said BOVs.

I wouldnt worry about it if its up in the engine bay, but it could be an issue if its exposed to road debris and whatnot.

Have you ever put your hand next to a bov? Even at the highest of vacuum it is still pushing air out. How the fuck will anything get in there if it ABSOLUTELY NEVER sucks air in? Ever. As long as the turbo is spinning there is positive pressure in the system exiting through the bov when its open.


That said I don't think it matters much, but seeing how MOST or ALL OEM systems come with one post intercooler I'd stick to that.

I put mine rite next to the tb but only because it shortens the length of hose needed for the reference signal from the im and there was room to fit it. I don't think there will be a difference in performance having the diverter valve mounted on either side. Lets see some pics of the proposed routing!

I did not know that. I guess it makes sense, since you do have a decent pressure differential from one side of the Tb to the other at idle. I just ASSumed that you needed at least a few psig positive pressure in the IC plumbing to cause any opening. So with vac in the ic plumbing, no open at all.

:facepalm: on my ignant azz.

Under idle/light cruise conditions there is probably a bit of vacuum in the ic plumbing. Small, but a bit. How could the BOV then have air going out? That would be a major PITA for tuning with any MAF based EMS, as it would basically cause the car to run rich all the time.

Well in my understanding and don't quote me on this one, if I put my BOV by the TB I will get faster spool from shift to shift since the IC would stay charged while the TB is closed. Now if I put it on the hot side I will loose some spool but I will save my turbo a little more from compression surge. Like I said I'm not an expert

as long as the compressor wheel is spinning it is moving air.
as long as the engine is on, the compressor wheel is spinning.

The only time I could POSSIBLY see the bov actually sucking in air is for that SPLIT SECOND when you stab the throttle and the car gulps in more air than is already moving through the system and the bov hasn't shut yet. We're talking less than a second worth of "sucking" time.

My mom always told me, cold side.

This is the cold side where my hand is there a circle I made with a market that's where the BOV would go
Attachment 199176

This is the hot side at the end of that there's a 180 deg pipe not pictured
Attachment 199175

I don't think there is a clear advantage either way, but the valve ought to be at one end or the other.

If a recirc, after the IC lightens the heat load very slightly. But, the work to push thru the IC is also very slightly greater thus the turbo would lose rpm quicker. Damn little.

My preference is at the TB end and it is, as stated earlier, to keep air heading one direction, and the IC a tick less drained.

Note that modern OEM's are now building it into the compressor housing. I hope Porsche doesn't succum to that approach.

Corky

The compressor wheel is spinning, but youre totally neglecting that the engine is still drawing in air. What makes you think that the compressor is ALWAYS pushing more air than the engine is taking in?

But anyway, even if it is a rare occurrence, which I agree that it probably is, it still could happen, and if your BOV is 2 inches from the ground you could possibly suck something up.

OP, that location looks great to me, I would put it anywhere in that reigon where its out of the way.

Edit: Hey how vague can I be :facepalm: I am refering to the coldside piping that you hit with the marker. One thing thats nice about that point is that you can do a piece of straight pipe there and thus have some real variability in the direction of the BOV, You can rotate the pipe to keep it out of the way and all.

not really. I've put my hand up to the bov on my car as well as many others while idling, and while revving, and while stabbing the throttle suddenly, each time it was exactly the same: at idle it was pushing out air, at slow revs it was pushing out air, at stabbing it would close super fast but before that it would be pushing out air. There was not one single time where I could get it to suck in air. And I TRIED to get it to do that.

That's just my experience though. Maybe some cars actually do suck in air through the bov. I don't know:noob:

I think the Lord thy God Has spoken and may it be so...Im putting mine about 3" away from the Throttle Body for the as above stated reasons.
(G)

lol, you said MAF based EMS.

Mine's always letting out air unless there's positive pressure in the manifold to keep it closed.

Mine used to let air out at idle untill I tighten the adjustable spring

+1 on above - wherever it is easiest to place.

Just make sure your not going to have clearance problems with your diverter and cooling fans/radiator. My old setup had the diverter pressed against the cooling fan, it was a major pita to install and uninstall.

I agree, but pressure is going to "stay" on one side of the intercooler longer, and I'd rather vent at the turbo-side of the piping because it dumps air more efficiently for the turbo and may help it free-wheel...but I think the advantage will be miniscule.

Anyone that tells you "compressor surge" off the throttle is a problem is a certified moron and you should not believe anything else they say.

weld it to the intercooler, i didnt try it on my evo but some people i knew had the setup on their evos, ams did it on many of their cars. just a thought

Pressure is pressure, but mass and velocity can co-exist in separate conditions under the same pressure. If boost is vented to atm near the TB then the turbo stays spooled and probably increases RPM. All air post compressor to BOV keeps it's velocity. Then when TB is opened the only air that has to start moving (still under pressure) is from the BOV to the TB, not compressor, IC, piping and TB. If this was not important why to we even bother with "tuned" intake manifolds?

My :2cents: :makeout:

This isn't club fagster: we don't do shit to be "different".
Makes sense. So you're saying coldside bov placement is better, right?:D

Seriously you guys are overthinking this one, and this is coming from an R&D Engineer who tends to overthink everything. Just place it where it is easiest.

I had my BOV on the hot side of the IC. Then when I switched to a Tial Q (big, like my penis) it would not fit on the hot side. So, I moved it to the cold side. All else was the same, and I did not notice a difference. Really, no big deal.

And welding it to the IC tank is not a bad idea if it is convenient. Why not? I considered it because it is a naturally good location clearance-wise for a v-mount setup when placed on the 'inside' of the V.

As long as it isnt like this, youre cool.

Attachment 199162

I think best location would be on the exhaust manifold

I think the best location would be in my butt :jerkit:

seems to me like thats not true b/c you have a person asking where he should place his bov. If yall didnt do shit to be "different" he would be putting the fucking valve where every other person places their valve. Come to think of it the thread wouldnt even be here.

The bov on the intercooler has a purpose. The only difference is there are not any miatas running 40-50psi.

Cool story, bro.

I read that placing the BOV near the TB increases the response time, to the detriment of the turbo. The inverse was also proposed. I don't have any data to confirm this theory.

I put my BOV on the hot side piping just after the compressor. I went this way because I inject meth on the cold side piping just after the intercooler.

I had my friend weld it on the cold side before the TB like I had it before. I should get the pipes back this afternoon and if everything goes well I'll clean them up and install them tomorrow. I'll post pictures and I'll let you guys know if I feel a difference between my old starion and this cxracing one. I'll also let you guys know if my AIT dropped at all or increased. Thanks guys for your opinions.

From memory on my old MSM it was just before the throttle body, if that counts towards anything.

https://www.miataturbo.net/forum/t5408/
https://www.miataturbo.net/forum/t17489/

Yeah i know.. I wana be like Mr Rogers the story telling master.