Run dual BOV's?

[sweet97]

Anyone running 2 BOV's or heard of it? I have tried a Forge, stock 1G w/dodge mod and have a Tial on order but am not confidant the Tial will solve my problem. Heard mixed responses from guys using the Tial and the different springs they offer also like Forge. Problem is running 25+ PSI and not having the valve blown open by the boost, ALSO it must not "flutter", cause compressor surge, at light throttle boost situations. Comments/advice welcome! Thanks, mark

 

[Maglin]

Well a 1G BOV modded will hold 30 PSI without leaking. I know cause I have pressure tested my modded 1G BOV to 35 PSI and it doesn't leak one bit. It will leak however under high vacuum which kind of sucks but not that big a deal if you use a blow through set-up. I personally need to run 2 BOV's if I want to stick with the 1G BOV as at 28 PSI with my turbo has compressor stall. At only 10 PSI which I can hit with my stutterbox their is so much air coming out of the BOV that it kicks up dirt in front of the car. If you are running very high boost levels it's pretty hard not to have flutter under cruise and low boost DD. I have it. I live with it. My BOV you can hear moving and everytime I let off the throttle it blows off. Gets really annoying but at least it's working somewhat. I've been told the Forge unit is larger and will work for most large turbo's. I think I'm just going to go with a 50mm Tial BOV as that is large enough for just about anything.

 

[sweet97]

Dodge mod got me to about 25psi but I am set for closer to 30psi with the actuator I prefer, a quick AGP billet piece. Also got surge now with the dodge mod. I can just add a source to the open hole with a nipple added to go back to stock but can't use my Holset like this!!:>(
I have gotten mixed responses to the TIAL even causing surge for some. Seems like 2 valves, TIALS, would equalize the pressure quickly enough to stop the darn surge, flutter, whatever you want to call it. It's what a BOV is supposed to prevent!! Mark

 

[Maglin]

Well I'm running a HX-35. The BOV isn't going to stop surge under cruise. That is from a wrong hot side AR. I do have surge if I cruise under low RPMs. So I just had to adjust my driving habits a little. Personally I'm going to go to the non wastegated full T4 Holset 9cm^ Turbine Housing instead of this POS Bullseye Mitsu internally gated one. The bullseye housing is killing the top end cause of the small scroll area. Just builds way to much backpressure past 6.5K RPM. I'm getting some mad creep cause of it. It's funny people worry about creeping to 20 PSI. IF I go to 8500 I creep to 29 PSI.

Anyways. Your not going to get rid of compressor surge with any type of BOV. But the stall is caused by the BOVs inability to let off enough air fast enough. I can't see the Tial not being able to handle it alone. I've debated on running 2 1G BOV's as that should be enough to take care of the compressor stall.

But do what you want. I like the low sound of the 1G BOV and The TIal will sound just a tad lower if sound is one of the things you are looking for. I personally hate high pitched BOVs like the SSQV. Even though I want to run 2 SSQVs as they don't leak, but neither does the Tial. If their BOV is anyways similar to the way their wastegates operate it will not open unless it is supposed to by vacuum.

 

[paul s]

I have solved my BOV problems by getting the Greddy typeR valve. it has 50mm outlet and a pretty stiff but adjustble spring..

 

[sweet97]

Maglin please describe the difference in what you are calling surge and stall. I can't believe the turbine housing has anything to do with compressor surge. If the BOV balanced the pressure difference as it should there would be no surge. Stall/surge are the same to me, the turbo slowing too quickly because the compressed air is backing up with no where to go due to BOV's not capable of handling the amount of charge air. The BOV opens and closes rapidly instead of releasing enough air the first time it opens. I should not have to change my driving style either. Tried and there is still flutter/surge/stall as I can't close the throttle quick enough.
Paul please describe your trials and tribulations with this issue. What BOV's did you try, actuators, boost, etc. This has become a major hassle ruining what little driving time the northeast affords me.
I'll do 2 TIALS if someone can tell me it would work for CERTAIN!! I get one tomorrow with a 9# spring. Mark

 

[sweet97]

Well a 1G BOV modded will hold 30 PSI without leaking. I know cause I have pressure tested my modded 1G BOV to 35 PSI and it doesn't leak one bit. It will leak however under high vacuum which kind of sucks but not that big a deal if you use a blow through set-up. I personally need to run 2 BOV's if I want to stick with the 1G BOV as at 28 PSI with my turbo it will have pressure stall. At only 10 PSI which I can hit with my stutterbox their is so much air coming out of the BOV that it kicks up dirt in front of the car. If you are running very high boost levels it's pretty hard not to have flutter under cruise and low boost DD. I have it. I live with it. My BOV you can hear moving and everytime I let off the throttle it blows off. Gets really annoying but at least it's working somewhat. I've been told the Forge unit is larger and will work for most large turbo's. I think I'm just going to go with a 50mm Tial BOV as that is large enough for just about anything.

What do you consider the difference between flutter/surge and "pressure stall"? Also where did you hear the Forge BOV would work for most large turbo's? Thanks, Mark

 

[94Jettameowpsst]

Most VW's w/ like to4e's and larger units like that run forge bov's w/ no problem. I used to be a dub owner myself and im gonna say about 7 out of 10 run forge, the other 30 percent use Tial.

 

[sweet97]

I tried the Forge that bolts to the stock 1G flange and it did not work for me. Tried both the dump and recirculate units. Surged badly but the guys at Forge treated me terrifically refunding my payment 2 weeks into testing the various springs. Mark

 

[CanadianTSi]

I run a Forge flanged for a 1G, holds 24psi just fine and never flutters although under low boost it sounds like a high pitched whistle

 

[sweet97]

Do you vent or recirculate? Which spring are you using and any idea what causes some to flutter? I just want my set-up to operate like it should but am at a loss as to what the problem is and whether it is unique to my system. Thanks, mark

 

[CanadianTSi]

I recirculate.

It's has whatever spring SBR ships in it, I'd assume it's pretty hefty though because it take at least 10-15psi to make it sound right otherwise as i said you get a high pitched whistle.

 

[dragrush]

My friend with his SR20 240 actually got rid of his surge problems with dual BOV's.

 

[sweet97]

I get the flutter/surge at part throttle conditions when it brings me into boost, like 10PSI but not WOT. It shakes the car at it's worst and is just very loud at it's best, opening and closing the BOV very quickly ubtil the pressures equalize.
Some guys have no proiblem with a GReddy type "R", A TIAL and a Forge. Others have the problem with the same identical valves. If it bucks the car it's not acceptable. A little flutter would be acceptable, shaking the car is not. MUST be an answer as guys with mnore powerful cars than I are avoiding this phenomenom for "some" reason. I can't figure it out though one guy said ny internal wastegate could be the problem though I don't see how. There must be a cause for this and my motor. Mark

 

[hellotbone]

I run a Forge flanged for a 1G, holds 24psi just fine and never flutters although under low boost it sounds like a high pitched whistle

I run the 1g Crushed and same here the whistle.

 

[Maglin]

What do you consider the difference between flutter/surge and "pressure stall"? Also where did you hear the Forge BOV would work for most large turbo's? Thanks, Mark

Pressure stall was supposed to be compressor stall. Now I know what you are referring to as surge. It's just BOV Flutter that you are talking about I think.

Here is the difference between each for your questions.

1. BOV Flutter is just that. Under low boost setting when you back off the throttle slightly the BOV will flutter and is definitely audible. (Sp) This is I guess what you are talking about.

2. Compressor Surge is where you pass the turbo's surge line on it's compressor map. It's hard to really explain. But the surge line will move down when you go to a small AR hot side. It's a loud sound that comes from the turbo. It is the pressure bouncing off the throttle body as it's during cruise mostly closed. The BOV isn't opening as their isn't all that much VAC acting on it as you are probably between 5-0 inhg. The pressure bounces all the way back to the turbo and doesn't stop it as it's not really spinning all that fast but it's slows it down and doesn't allow any airflow through the compressor even though it's still spinning which causes the barking. It isn't to harmfull for most turbo's but it does slow it down and will hurt your spool coming right out of compresser surge.

3. Compressor Stall is when the air hits a closed throttle plate and bounces back to the compresser wheel completely stopping it. The throttle is closed so their is little to no force acting on the turbine wheel to try and get it spinning again. The sound is similar to compresser surge Sept way louder. Noise is caused by the same thing basically. I work on Jet engines and When they stall the compressor is still spinning but their isn't any airflow through the intake as it's just stalled in the compressor. (caused usually buy a stupid new pilot that is yanking on the throttles violently), or by a bleed air valve not opening or out of sequence. The bleed air valve is basically the same thing on a jet engine that the BOV is for out turbo cars.

Sorry I was a little tired and getting ready to move when I posted that last post and messed up what I was even saying. I'll revise the post some. So anyways when the compressor stalls all that rotating inertia usually goes from rotational to directional and places a very large load on one side of the thrust bearings and start causing premature wear. A BOV that is to small will do the same thing just not as violently which happens to be my case. Compressure sure happens cause your under vacuum and your small AR hot side is spinning the turbo up and trying to build boost even though your foot hasn't called for it. It's mainly a pressure differential thing. That is why I say a hot side is a factor for surge and that is why I said what I did.

Yes on highly boosted engines seems like a fine art to not get flutter or a leaking BOV under high boost. Don't really know why. But as I said before. If the Tial BOV is made similar to their wastegates you wouldn't need a heavy spring in their to kept it closed under high boost as it's design hardly allows you to open their wastegates by placing pressure on the valve it's self.

 

[sweet97]

It's all surge to me if the BOV flutters. The BOV is supposed to prevent this. Where did you hear that the Forge valve was good for the big turbo's?
I have my TIAL on but the original 1G BOV is there but not hooked up and so far the results are positive. I can hear the TIAL blow off when lifting the throttle and no surge/flutter. I need to fashion a plate to remove the 1G valve and cover the flange. Then I will try the boost higher and hopefully reach the 25+PSI the Holset should run.
I have had surge at 5 psi that shook the car violently. That is not good. Same thing at any boost with PARTIAL throttle when the amount of throttle begins to level off or I lift off the throttle slowly. In my opinion if the valve is fluttering then that is comp surge because it means the turbo is changing speeds quickly, again, bad. Hopefully the TIAL will be the answer. Mark

 

[Maglin]

Well slightly off topic. How are you liking your Holset? I've just moved up in elevation a bunch and of course I lost a little bit of fun. Today when it was 100ish outside the car still feels great and also likes to knock at 25 PSI. It's funny as it was boosting to 19-20 PSI now it is boosting to 15 PSI. Now I can finally have my EBC hooked up and maintain a fairly steady boost pressure with the stupid internal gate.

 

[94Jettameowpsst]

It's all surge to me if the BOV flutters. The BOV is supposed to prevent this. Where did you hear that the Forge valve was good for the big turbo's?
I have my TIAL on but the original 1G BOV is there but not hooked up and so far the results are positive. I can hear the TIAL blow off when lifting the throttle and no surge/flutter. I need to fashion a plate to remove the 1G valve and cover the flange. Then I will try the boost higher and hopefully reach the 25+PSI the Holset should run.
I have had surge at 5 psi that shook the car violently. That is not good. Same thing at any boost with PARTIAL throttle when the amount of throttle begins to level off or I lift off the throttle slowly. In my opinion if the valve is fluttering then that is comp surge because it means the turbo is changing speeds quickly, again, bad. Hopefully the TIAL will be the answer. Mark

I know this whole topic is about big turbo's but a tial bov on my evo 3 under part throttle and partial boost and such sounds like a turkey in a blender

 

[sweet97]

You need to re-read what flutter and surge is. They are not one in the same. Just because the BOV is fluttering, does not mean your turbo is surging.

My TIAL flutters all the time, under 10psi of boost, mostly because its 1 ####ing tight ass spring. But even on a small rev, I can watch the piston move on it.

If your car starts bucking, or sounds like the video I posted up... then your having some serious problems. If its related to low boost blow-offs, then I would suggest a smaller spring weight; or just run a regular quick release BOV like a 1g(UNMODED).

I was getting a hard bucking(5PSI/stiff spring) which I call surge and just because that lessens to a flutter(no bucking but the "turkey gobble") I still consider that surge. IMHO a BOV should be designed to eliminate surge/flutter.
Stock BOV would not hold 25PSI even with the dodge mad. Actually the dodge mod made it into a fluttering BOV!
I do believe I will be fine now and hopefully with the one TIAL. No flutter at any boost so far. It was part throttle boost that was the biggest problem. Heavier springs made it worse. The Tial has a white spring and I think it's a 9# spring. If yours flutters a 7# or lighter than what you have would help. You're right, they sure are tight springs. Ay first I thought something was wrong with mine as I could not push it open but pushed really hard with both hands and it opened!! I should get the 1G out of the system today and then see what the TIAL will do. If a particular BOV releases enough air when it first opens there should be no flutter as it would have equalized the 2 different pressures immediatly. I don't understand why a stiffer spring causes this phenomenon to occur more easily. Emailed David Buschur and he said running big turbo's have the trade off of some flutter and if I could not live with the flutter to change the turbo. As long as the flutter is not damaging I can live with a little but will try to fine tune the BOV to eliminate it even if it requires 2 BOV's to equalize the pressures more quickly. Mark

 

[sweet97]

Well slightly off topic. How are you liking your Holset? I've just moved up in elevation a bunch and of course I lost a little bit of fun. Today when it was 100ish outside the car still feels great and also likes to knock at 25 PSI. It's funny as it was boosting to 19-20 PSI now it is boosting to 15 PSI. Now I can finally have my EBC hooked up and maintain a fairly steady boost pressure with the stupid internal gate.

Not really off topic as the Holset is what seems to have caused the issue. I like it. Amazing how smoothly the wheels spin and for how long, almost like a BB supported shaft instead of the 360* thrust bearing it has. Spools very quick once it starts. I was getting 25PSI by 4500RPM's, about the same as my 60-1. I need a 4" intake which is coming to make better use of the MWE air inlets. Mark

 

[Maglin]

The flutter is from a heavy spring. At low boost it opens and closes from the heavy spring pressure. Your 1G BOV is probably leaking at high boost if it's not hooked up to a boost source. I love the "Dodge mod" 1G BOV. Mine is holding to 35 PSI like I said.

I'm glad you are liking the turbo. Your bucking is probably compuressor surge at low boost levels. And that can be eliminated by running your gears a little longer in the RPM band for normal driving. Like I said I get surge if I lug the turbo and shift and 2.5-3K for street driving. Now I just shift at 4K and don't have the surge. I still have BOV flutter but that isn't going to hurt anything. it's just annoying. And yes once my turbo hits about 12 PSI I'm at 25 PSI in a blink of an eye.

I'm also very glad to hear that the Tial BOV is simular to their wastegate. I can't open that at all with two hands. If I just suck on the lower vacuum nipple I can feel the valve move a tiny bit. Mine wastegate has a .8 bar spring in it. If I'm bored today I'm going to go probably hit up a casino and probably just bet all my spare money on red or black on roulette. If I win I get to buy some car parts. If I loose then I guess I'll have to wait a little longer. On a side note I have a buddy that kepts winning $1,700 like every 3 weeks. It's starting to really piss me off. It's paid for his 22's. Tons of toys and now his 2G.

 

[sweet97]

Well the TIAL is on and no more surge!! I can boost to 10psi and hold it there and it's just fine. It seems a bit slow to react and blow off but it's functioning the way I had hoped. I got a little "blip" when at 20psi for a few seconds that may be from a faulty coupler. I have one that is not silicone. I need a different lower IC pipe to correct that. So good news. Mark

 

[Defiant]

No, I don't know why I left this open so long. My apologies.