School me on blow off valves

[99riocobra]

alright guys, i'm gonna hopefully be setting up my next turbo setup with blow through maf. so i'll need a blow off instead of the bypass the hellion kit comes with. so i had a few questions about them if anyone wants to chime in...

1) can the turboXS valve be used as an atmospheric blow off also?
2) from what i understand a vacuum line going to the bov will keep it shut under boost and when in vacuum(between shifts) the bov gets pulled open. so why do you have different spring rates to choose? is the bov slightly open durring idle?
3) the bov needs to go anywhere in the charge piping before the maf correct?
4) any other bov's people have had good luck with? i see some go with the tial but i'm not a huge fan of how it sounds...any videos would be cool

any other info will definitely help, thanks!

 

[Janstang]

1)I used the Turbo XS in a blow-off config. with no issues..
2)Correct.. I used the stock spring with mine. I believe the different springs are for cases where guys may have some surge issues. By changing the tension of spring you can help with this issue.
3)Mine was located post intercooler(approx. 10-12in. from the intercooler outlet). Prior to the MAF if doing a blow-thru config.
4)I'm going with Tial on the new setup. I also really like the red Procharger Race bypass/blowoff valve.
What size turbo you going to be running? What kind of power you hoping to make?

 

[TRBO VNM]

I have used the turboxs on setups I have done as well, no issues.

I would place it between the turbo and intercooler. That way it will bleed off hot air and not the already cooled air.

some companies like Tial are specific on their spring rates based on the vac. of the motor. some you put spacers(washers) in or have a set screw to apply more pressure.

 

[99riocobra]

1)I used the Turbo XS in a blow-off config. with no issues..
2)Correct.. I used the stock spring with mine. I believe the different springs are for cases where guys may have some surge issues. By changing the tension of spring you can help with this issue.
3)Mine was located post intercooler(approx. 10-12in. from the intercooler outlet). Prior to the MAF if doing a blow-thru config.
4)I'm going with Tial on the new setup. I also really like the red Procharger Race bypass/blowoff valve.
What size turbo you going to be running? What kind of power you hoping to make?

I have used the turboxs on setups I have done as well, no issues.

I would place it between the turbo and intercooler. That way it will bleed off hot air and not the already cooled air.

some companies like Tial are specific on their spring rates based on the vac. of the motor. some you put spacers(washers) in or have a set screw to apply more pressure.

oh this is great to know. i kind of thought i could use the turboXs one that comes with the kit but i never saw anything on people using it...

ok, so neither of you guys have surge/flutter/whatever issues with the stock spring that comes in that one? do you use any washers in it?

and if i'm thinking right, the valve will be pulled open durring udle then right? is that how they all work and just blow air all the time under vacuum?

yeah i planned on running it on the bend in the bumper right before going into the intercooler. i'll be running the turbonetics 76mm .96ar in the Hellion kit. hoping for around 725rwhp/700rwtq on pump. to be honest as long as my torque goes up just as much as my hp this time i'll be a happy camper. gaining 175hp and only 50tq with a 8 psi increase wasn't the most fun thing....

thanks for all the help guys!!

 

[Juiced46]

oh this is great to know. i kind of thought i could use the turboXs one that comes with the kit but i never saw anything on people using it...

ok, so neither of you guys have surge/flutter/whatever issues with the stock spring that comes in that one? do you use any washers in it?

and if i'm thinking right, the valve will be pulled open durring udle then right? is that how they all work and just blow air all the time under vacuum?

yeah i planned on running it on the bend in the bumper right before going into the intercooler. i'll be running the turbonetics 76mm .96ar in the Hellion kit. hoping for around 725rwhp/700rwtq on pump. to be honest as long as my torque goes up just as much as my hp this time i'll be a happy camper. gaining 175hp and only 50tq with a 8 psi increase wasn't the most fun thing....

thanks for all the help guys!!

If you want to pick up TQ put a .81 housing on that turbo it will pick up a ton! I run the Turbo XS valve with my blow thru config it works just fine. No washers. I mounted it on the bend before the IC.

 

[carolinacat]

The bov is held shut with the spring and boost pressure... which is applied to the diaphram in the bov. When the throttle body shuts the motor has vaccum again and causes the bov to open and bleed the boost pressure off in the charge pipe. When the pressure difference equals the bov shuts and under normal vaccume the spring pressure holds the valve shut. They recommend that the Bov be placed close as possible to the throttle body but you can only place it so close when running a blow thru application.

 

[99riocobra]

If you want to pick up TQ put a .81 housing on that turbo it will pick up a ton! I run the Turbo XS valve with my blow thru config it works just fine. No washers. I mounted it on the bend before the IC.

nice, so i can just use it right out of the box! yeah, i've thought about the .81, i jst don't want to choke it up top i guess. i can always change down the road i suppose...

The bov is held shut with the spring and boost pressure... which is applied to the diaphram in the bov. When the throttle body shuts the motor has vaccum again and causes the bov to open and bleed the boost pressure off in the charge pipe. When the pressure difference equals the bov shuts and under normal vaccume the spring pressure holds the valve shut. They recommend that the Bov be placed close as possible to the throttle body but you can only place it so close when running a blow thru application.

yeah i understood how they worked for the most part. i most definitely forgot about the pressure being the same in the vac line and in the piping durring all conditions except a sudden closed throttle, therefore the spring would hold it shut durring idle :bash:. thanks!


Jason: does the TurboXs valve some with a weld on bung so i can mount it for blow-through? thanks.

 

[rotor_powerd]

Just about all blow off valves are open a slight bit during idle , but if it is located pre-MAF, it isn't that big of a deal. If it was post-MAF, you'd have a vacuum leak. Blow off valves like the HKS SSQV are closed during idle. Boost pressure will snap it shut once you start making positive pressure, though.

 

[TRBO VNM]

Jason: does the TurboXs valve some with a weld on bung so i can mount it for blow-through? thanks.

typically it doesn't since they are welded to the s pipe, but I can get you one or you can get one directly from tuboxs.

oh yeah, and I think hellion does have another option for BOV's now. I can't remember the brand. I think it is turbo smart. That or it is the wastegate. lol

 

[99riocobra]

Just about all blow off valves are open a slight bit during idle , but if it is located pre-MAF, it isn't that big of a deal. If it was post-MAF, you'd have a vacuum leak. Blow off valves like the HKS SSQV are closed during idle. Boost pressure will snap it shut once you start making positive pressure, though.

yeah even if it's open some it won't really matter before the maf.

typically it doesn't since they are welded to the s pipe, but I can get you one or you can get one directly from tuboxs.

oh yeah, and I think hellion does have another option for BOV's now. I can't remember the brand. I think it is turbo smart. That or it is the wastegate. lol

alright well i'll probably need one from ya then when the time comes. hmm, well if the TuboXs as a bov works fine i'll probably stick with that.

 

[BOSS 32V]

I run the big red procharger race bov, it's stays open at vacuum and closes at wot.

 

[Juiced46]

If you are looking to pick up a BOV. I would go with a Tial Q. You can find them for around $200. Or just cut the flange off the bottom of your S pipe on your Hellion kit and reweld it where you want. I think I have an extra flange that I cut off laying around if you want it.

 

[99riocobra]

i'm probably gonna stick with the standard turboXs one for now. it's simple and i like the sound better than the tial...will do. i'll hit you up if Jason doesn't have a spare laying around already. thanks!

 

[2bscrewed]

I run the big red procharger race bov, it's stays open at vacuum and closes at wot.

I have that one also, but we cranked it down til it was closed at idle, because when it was open, it was messing with the MAF counts.

 

[99riocobra]

hmm, interesting. even though it was pre maf? how far before the maf was it mounted?

 

[Janstang]

I have that one also, but we cranked it down til it was closed at idle, because when it was open, it was messing with the MAF counts.

Kind of defeating the purpose of the blow-off valve if you've got it cranked shut at idle-Isn't it? I'd be repositioning it elsewhere before I closed it down completely at idle..

 

[2bscrewed]

hmm, interesting. even though it was pre maf? how far before the maf was it mounted?

It was about 16-18" from the MAF. I am using a 3.5" intake tube, so my MAF counts were already pretty low at idle, so any turbulence would throw the MAF off considerably.

Kind of defeating the purpose of the blow-off valve if you've got it cranked shut at idle-Isn't it? I'd be repositioning it elsewhere before I closed it down completely at idle..

No, it blows off when it's supposed to. At idle it doesn't really blow much air out on a turbo car. The compressors aren't really moving much air at idle.

 

[99riocobra]

hmm, so from what it sounds like the bov can vent air at idle or it doesn't have to. as long as your car is tuned accordingly...

 

[BOSS 32V]

I have that one also, but we cranked it down til it was closed at idle, because when it was open, it was messing with the MAF counts.

i don't have any issues with the bov open at idle and i also run 3.5'' piping...

I don't understand how yours is closed at idle and it opens up when you let off? idle is when the motor sees the most vacuum.......?

 

[99riocobra]

not necesarily. next time you get on it through say 3rd gear, let off the gas at the end say 5-6k and watch your boost/vacuum gauge on initial decel/engine brake.