Install ? For those with BOVs

I have installed a Tial BOV on the up pipe before the throttle body and wanted to know which vacuum line to "tee" into. I read somewhere that the line you tee into must be at least 1/4" or straight to the intake. I am currently tee'd into a 7/32" vacuum line that goes from the vacuum block to the canister near the air filter. The hose I'm using from the bov is 1/4". With this current install, the turbo still "sneezes" when I let off the throttle, no whoosh sound. So I'm not sure if i am tee'd in the right line. The setup I have is a PT67 running a minimum 21 lbs on alky. I also have the vacuum brake setup. If you have any pictures of your working setup (close up of the tee'd vac line), that would help me out a lot. Thanks.

Is the valve adjustable? If so is it set properly? If it's not adjustable then it'll have a certain pressure rated spring in there, make sure it's the right tension spring. My BOV has an adjustment screw and didn't work right when I installed it either, had to loosen up the tension, it was holding closed too tightly.

I don't think I even paid attention to which vac hose I picked, just grabbed one and went with it.

I "T" mine off right at the MAP sensor... works perfect... i did have to play around with spring tension to get it where i wanted... it took some aluminum washers and a mityvac to "dial" in everything.... HTH

As far as I know, it is not adjustable. I took apart the valve and looked at the spring. It is silver in color (not painted). According to the Tial website, it says if you are running 18 - 21 in/Hg @ idle, to use the un-painted spring which i have. The car has vacuum at 18 -19 at idle.

Hello TA81,
I installed a Tial Q 50mm bov and I am having some issues also. I have a unpainted (10lb) and white (9lb) spring. I am tee'd into the map sensor vacuum line. I am pulling 15-16Hg/in of vacuum at idle (warmed up).

When I am using the 10pm spring, the bov doesnt react/open as fast as it should, but it will open up about half way when I Am opening and closing the throttle door. When I am driving the car, the bov half way functions, but there is still turbo fluttering.

When using the 9pm spring, the bov opens and closes better. But at idle the bov doesn't seal completely. It will fluctuate slighty while idling.

Did you fix your tial bov issue? If so, what was your solution?

Wiseman,
I went to Lowes and picked up 5 washers about 1/8" thick the same dia as the spring. I then installed two washers, test drove and everything works fine now. You'll have to experiment with the thickness of the washers to see what works for you. HTH

Hello TTA81,
Thanks for the response. I have picked some washers up. I was also curious of:
1) Did you tee into the map sensor vacuum line (if so do you have a boost gauge tapped into this same line also)?
2) Did you add the washers under the spring or above the spring?

Thanks!

I have a question for you guys running BOV's, if you are using the stock maf, are you recirculating it back into the intake pipe or just venting it?

With my UICP setup I can make it all recirculate pretty easy but if doesn't mess with the car to much, I can just vent it for the sake of being, even easier (lazier)

Hi Dennis,
I am not running a stock MAF. I am running a 3in LT1 MAF and a tial 50mm BOV (Q-Series, non recirculating). It took me a while, and a lot of trials and effort to finally get the right spring combo, but it is finally working correctly. My BOV is vented to atmosphere and i am not using alky. There are a number of posts that have feedback of why you may want a recirculating valve over a valve that vents to the atmosphere. I believe if you are running alky, you may want to use a recirculating valve for safety.

I wouldn't think which maf you are using makes the difference, I would think placement would be the deciding factor.

If I were to run a vented BOV, after letting off the throttle all that metered air would go unaccounted for and cause a overly rich condition. Recirculating it back into the intake pipe between the maf and turbo compressor *should* take care of it.

However if I can get away with venting and the car runs fine, it would be easier for me to set it up. I am never going to use alky, I am all boost and a pump gas kinda guy, but I am putting in a new turbo tomorrow and I can get all this done sort of thing while I am in there.

Ive been running a BOV vented to the atmosphere for years and never had a rich condition, tip in stumble post BOV ops, sparkplugs fouled, etc...never had a issue. This is before the GEN2 on the bone stock ecm and MAF as well as GEN2 with stock, LT and LS sensors.

I tie into the fuel vapor canister for the vac signal.
Steer clear of using the MAP line IMO that should be a dedicated line as well as the Fuel PSI reg should.
The spring is going to affect the vac signal that opens the BOV, with a spring that actuates too fast/easy as it will open the BOV in a high vas situation like engine braking in 3rd, etc.
Easy way to tell if the spring is too light is to have someone hold the car at 2.5 or so rpm for a bit from idle and watch feel the BOV piston for movement. That no load higher fixed rpm will generate a higher vac than idle and give you a general idea dn you can adjust from there.

I can't see a BOV causing any appreciable change in AFR (when opening upon lifting of the throttle) if you DONT recirc...... it would be different if you were using it somehow to stay open until the turbo was spooled all the way up.......

Thanks for the tips!

On my Evo and my now gone DSM, the bov is recirculated from the factory (both 5spd cars) and both are maf cars. If I had them vented and shifted, bov would open, it would cause a rich condition. AFR gauge would peg 9:1 and stay for a second and car would run like crap for a second as well, stumble and sometimes miss-fire when I got back on the throttle.

The Evo I resolved this by switching to speed density. I just want to make sure I can do this and if I don't have to recirculate this it makes my life a lot easier! My uicp is mild steel and easy for me to weld, the intake pipe is aluminum and I don't think my welder is up for that job. It will also make placement a lot easier.

Forgive me for having LC2 turbo v6 auto tranny blinders on...... My comment was geared toward turbo Buicks...... It might make more sense to recirc on a stick car..... I was imagining an auto car when you let off after a quarter mile run.....

I would not want it open during spool up or any time other then when the throttle is closed, say after a nice pull or whatever.

I know they don't come with them stock, but I can't help but wonder if having one would help. I also know there are a lot of auto's that DO have one installed from the factory.

I guess if a spring is tight enough to not ever crack open, venting it could be fine, but I think I should just man up and recirculate it. My opinion on them is not to help maintain spool on a stick shifted car, if you're going for the big win, it takes about .5 seconds to shift if you are a slow shifter, you won't loose that much spool unless it is a huge ass turbo.

I am much more concerned with relieving positive pressure in the cold side. I can't see how compressor stall is a good thing on my nice new turbo.

Another option is to run the lighter fast acting spring and limit the amount of vac going to it, yet not limit the pressure. Shims do work but they limit the overall travel of the BOV.

There is a company called Dejon Tool that used to make a boost actuated 3 port valve. It was a normally open valve and you would put a boost/vacuum source to the top port of a BOV (typically a modded 1g bov) and once you got to 14psi the spring would collapse and vent the pressure from the lower port so the BOV would stay clamped shut. When you let off the throttle the valce would open again, put pressure back to the lower port while vacuum hit the top port of the BOV and making it release fast.

Doesn't look like they make them much anymore, unfortunately, because they worked great. I suppose one could do the same thing with a HOBBS switch and an electric valve.

I just got my tial 50mm BOV (Q series) to start working correctly. Right now, I am running 10lbs of boost on my GN (new build). At 10lbs of boost I can hear it working really well. I don't hear any more turbo flutter when i get off the gas. At low boost it works good also, you can hear the BOV open, but it is not a loud swoosh, only a suddle one. Even at 10lbs of boost, the swoosh noise isn't loud, u can hear it but, it isn't as loud as i have heard some people complain about. I played with the spring for a couple weeks and finally was instructed to use shims. At idle, warmed up, I was reading 15-16Hg/in on my guage which matched up with a plain spring (10lb). This spring was too hard. It would keep the BOV from opening at idle, but it was too stiff and didn't allow the BOV to open once the petal was lifted ( and I was still getting turbo surge/ flutter). I contacted tial and they sent me a 9lb spring and the spring was soft enough to allow the BOV to open well once pedal was lifted, but the BOV would fluctuate open and close during idle. So, I used 3 (1/8in thick) washers as spacers and it works fine. At idle, it is not as responsive as the import videos on YouTube (plus it only opens up about 3/4 of the way when testing at idle). Under boost, I can't see how much it is opening, but I don't hear the turbo flutter (most important) and the BOV sounds much better than what it was with the 10lb spring.

With 15Hg/in on the vacuum gauge using a 9lb spring with 3 (1/8in) washers keeps the BOV closed during idle, and keeps the BOV reacting correctly with no turbo surge under boost. Of course I would've preferred no shims, but there is no "in between" spring between a 9 and 10lb spring.

I am curious about the shims, my understanding is the spring is linear, meaning that it is the same pressure no matter how much it is compressed.

I also think a lot of problems I have been reading about would be fixed if there was a recirculated tube after the maf and before the turbo inlet

When i spoke with the tial technician he told me to start with the lighter spring (in my case the 9lb) and add washers. By adding washers, it increased the spring stiffness that allows you to achieve a higher tension spring. In my case, since I added 3washers my spring has been increased to a 9.25 or 9.5lb spring. This is what I needed b/c the 10lb spring was too stiff (it was keep the BOV closed at idle, but was too stiff for the excess pressure to push the BOV open once I let off the gas causing turbo surge). The 9lb spring results was the complete opposite of 10lb spring. I knew I needed something in the middle of these 2 sizes, that tial doesn't offer. By adding shims, you essentially wind up creating a custom tailored spring force for your car.