Best BOV ever?!

[TurboStreetCar]

The amount of pipe between the turbo outlet and the BOV gives it a bit of a buffer. No pipe, no buffer.

Well my point is the quicker you release the pressure at the outlet of the turbo the less flutter you will have. The same principal behind IJ cutting the spring to lower the pressure required to open the valve.

If the coupler came off the compressor housing at 20psi there would be no flutter when you let off because there would be no turbulent air rushing backwards threw the housing and compressor wheel.

Pressure slowing/stopping the compressor wheel is what causes the flutter, releasing that pressure as quickly as possible and not allowing it to push against compressor wheel is the whole point. How would having more tube or effectively more delay releasing this pressure by mounting the BOV further away increase the effectiveness of the BOV to reduce flutter?

Maybe im explaining myself wrong?

also just to add. the longer the vacuum line the more flutter too.

I agree with this as the longer this line is the longer it will take for the valve to react and open.

 

[super.secret.supra.club]

Well my point is the quicker you release the pressure at the outlet of the turbo the less flutter you will have. The same principal behind IJ cutting the spring to lower the pressure required to open the valve.

If the coupler came off the compressor housing at 20psi there would be no flutter when you let off because there would be no turbulent air rushing backwards threw the housing and compressor wheel.

Pressure slowing/stopping the compressor wheel is what causes the flutter, releasing that pressure as quickly as possible and not allowing it to push against compressor wheel is the whole point. How would having more tube or effectively more delay releasing this pressure by mounting the BOV further away increase the effectiveness of the BOV to reduce flutter?

Maybe im explaining myself wrong?



I agree with this as the longer this line is the longer it will take for the valve to react and open.

i can see how your thinking and by that means its right but thats just not how it works in real life. think about pouring sand in an empty water bottle. where sand can relate to air, the mouth of the bottle is the turbo outlet and the bottom is the TB the moment it closes. as the TB closes the compressed air is bunched at the TB and quickly move towards the turbo. if the BOV is close to the TB, it would open the moment vac in the manifold pull the BOV open before air was to rush back to the turbo

now if the BOV was near the turbo, it would still release pressure but since it has all built up behind the BOV near the TB it has sometimes more pressure than the BOV can handle, and in affect cause the flutter.

i hope you understood what i was trying to say ;p

 

[supranz]

also just to add. the longer the vacuum line the more flutter too.

I disagree, my bov has a long vac hose (about a yard in length) and I occur no flutter, bearing in mind mine is as far away from the turbos as possible (just before the throttle body)

 

[super.secret.supra.club]

I disagree, my bov has a long vac hose (about a yard in length) and I occur no flutter, bearing in mind mine is as far away from the turbos as possible (just before the throttle body)

well there ya go

im wondering why your hose is 3 feet long and your BOV is close to your TB, which means its close to the manifold, which means close to a vacuum source. why have it that long? also im willing to bet that your BOV would be much more responsive if it was done properly

 

[dumbo]

i can see how your thinking and by that means its right but thats just not how it works in real life. think about pouring sand in an empty water bottle. where sand can relate to air, the mouth of the bottle is the turbo outlet and the bottom is the TB the moment it closes. as the TB closes the compressed air is bunched at the TB and quickly move towards the turbo. if the BOV is close to the TB, it would open the moment vac in the manifold pull the BOV open before air was to rush back to the turbo

now if the BOV was near the turbo, it would still release pressure but since it has all built up behind the BOV near the TB it has sometimes more pressure than the BOV can handle, and in affect cause the flutter.

i hope you understood what i was trying to say ;p

I would also say having the bov at that end inertia helps the air out.

IJ, I may try tweaking my *humph* SSQV. Thanks.

 

[MA70Snowman]

well there ya go

im wondering why your hose is 3 feet long and your BOV is close to your TB, which means its close to the manifold, which means close to a vacuum source. why have it that long? also im willing to bet that your BOV would be much more responsive if it was done properly

actually thats a very good question.. lol didn't even hit me till you pointed it out. I was all "okay.. 3 feet of hose... and its right next to the throttle body, check! I see nothing wrong with that."

it would be nice to find some solid numbers on this. as Conversly If you had BOV that could flow the CFM, having it in the middle could also seem ideal. as you would have pressure comming from the TB pushing back and, pressure comming from the compressor going forward, and Ideally having the BOV in the middle where the two presures meet up would theoretically combine that force out the BOV.. ::shrug:: just a concept I could totally be comming from left field.

 

[CajunKenny]

^I think I understand what you're saying; but, the pressures don't "meet".

There's high and low pressure and the "flow" is from high to low. So, given your idea, placing the BOV close to where this transition happens would be ideal. However, the BOV is there to create the lowest pressure which makes it the transition point.

I would put more effort in finding a BOV that works best at a desired boost level than placement of the BOV. As long as placement is within the norm that is...

 

[MA70Snowman]

^I think I understand what you're saying; but, the pressures don't "meet".

There's high and low pressure and the "flow" is from high to low. So, given your idea, placing the BOV close to where this transition happens would be ideal. However, the BOV is there to create the lowest pressure which makes it the transition point.

I would put more effort in finding a BOV that works best at a desired boost level than placement of the BOV. As long as placement is within the norm that is...

like i said it was just a flight of fancy type theory.

As long as placement is within the norm that is..

i though "norm" was what we were talking about lol. at least defining it

 

[CajunKenny]

like i said it was just a flight of fancy type theory.

No worries. I wasn't playing your idea down. Just discussing it. I'm certainly no expert.

i though "norm" was what we were talking about lol. at least defining it

Well, I just wanted to be clear because I know the next post was going to be: "What if I put the BOV right on the compressor housing...!?"

 

[MA70Snowman]

No worries. I wasn't playing your idea down. Just discussing it. I'm certainly no expert.



Well, I just wanted to be clear because I know the next post was going to be: "What if I put the BOV right on the compressor housing...!?"

LOL, I didn't even think of that. I was expecting "intercooler" or manifold (yes there's no purpose at the point)

 

[TurboStreetCar]

i can see how your thinking and by that means its right but thats just not how it works in real life. think about pouring sand in an empty water bottle. where sand can relate to air, the mouth of the bottle is the turbo outlet and the bottom is the TB the moment it closes. as the TB closes the compressed air is bunched at the TB and quickly move towards the turbo. if the BOV is close to the TB, it would open the moment vac in the manifold pull the BOV open before air was to rush back to the turbo

now if the BOV was near the turbo, it would still release pressure but since it has all built up behind the BOV near the TB it has sometimes more pressure than the BOV can handle, and in affect cause the flutter.

i hope you understood what i was trying to say ;p

I think I get what your saying. That if the bov Is next to the throttle body when it closes the air will simply divert out of the blow off valve rather then turning back to the turbo.

I understand that view but I don't think the air has that much mass. I don't thin it has the inertia to keep the pressure flowing out of the blow off valve. IMO the pressurized air would instantly push back threw tge compressor housing the instant there isn't enough flow/push on the turbine wheel to keep it turning normally.

I can understand both sides of this though. It's an interesting situation.

 

[super.secret.supra.club]

lol, this thread is a win

 

[dumbo]

If you were hot flowing pressurized air, where would you want to go?

Needless to say, the HKS SSQV blows...and whistles while it does it.

 

[MA70Snowman]

If you were hot flowing pressurized air, where would you want to go?

Needless to say, the HKS SSQV blows...and whistles while it does it.

see dumbo thats where I gotta disagree with you. I ran mine for 5 years, no problems. From 8-16psi (I'll credit that I can't vouche for Higher boost ranges) Never experianced flutter, high or low. And Like I said before, I'm a fan of the sound, so for me thats a +1. I've ran Blitz and Greddy's, and each one had aspects I wasn't a fan of. Again from before, If I were to get a "High-end" BOV it would by synaptics, but so far SSQV satisfies me.

 

[GrimJack]

Ok, this is going to be long, but I'll try to address everything.

Well my point is the quicker you release the pressure at the outlet of the turbo the less flutter you will have. The same principal behind IJ cutting the spring to lower the pressure required to open the valve.

If the coupler came off the compressor housing at 20psi there would be no flutter when you let off because there would be no turbulent air rushing backwards threw the housing and compressor wheel.

Pressure slowing/stopping the compressor wheel is what causes the flutter, releasing that pressure as quickly as possible and not allowing it to push against compressor wheel is the whole point. How would having more tube or effectively more delay releasing this pressure by mounting the BOV further away increase the effectiveness of the BOV to reduce flutter?

You're close! The point you've neglected to factor in is what happens after you open the throttle again. If the BOV is mounted next to the turbo, you now have to re-pressurize your hot pipe, intercooler, and cold pipe again. We mount these close to the throttle body to help maintain boost between shifts.

i can see how your thinking and by that means its right but thats just not how it works in real life. think about pouring sand in an empty water bottle. where sand can relate to air, the mouth of the bottle is the turbo outlet and the bottom is the TB the moment it closes. as the TB closes the compressed air is bunched at the TB and quickly move towards the turbo. if the BOV is close to the TB, it would open the moment vac in the manifold pull the BOV open before air was to rush back to the turbo

now if the BOV was near the turbo, it would still release pressure but since it has all built up behind the BOV near the TB it has sometimes more pressure than the BOV can handle, and in affect cause the flutter.

A better analogy would be blowing compressed air at a computer fan - it will stop the fan and cause it to reverse direction. Of course, a computer fan isn't connected by a shaft to the hot side of a turbo. Because turbos have two wheels, you're then left in a position where the exhaust gas is trying to spin the assembly one way, and the compressed air coming from the direction of the closed throttle plate is trying to spin it the other way.

To elaborate a bit on my buffer post from earlier - if your BOV can handle all the output of your turbo, you'll never have a problem. With a non-functioning BOV, or without one entirely, you'll run into surge issues almost instantly if you're at boost and snap the throttle closed. With a BOV that can handle some of your turbo output, the surge will still move backwards from the throttle plate / BOV location, but it will move slower. Usually, you're done shifting before it reaches the compressor on the turbo.

I disagree, my bov has a long vac hose (about a yard in length) and I occur no flutter, bearing in mind mine is as far away from the turbos as possible (just before the throttle body)

Hate to say this, but this means you are lucky, not that the ideal of keeping your vac hoses as short as possible is invalid.

Also im willing to bet that your BOV would be much more responsive if it was done properly

Correct. Admittedly, it sounds like his functions fine, so why worry?

actually thats a very good question.. lol didn't even hit me till you pointed it out. I was all "okay.. 3 feet of hose... and its right next to the throttle body, check! I see nothing wrong with that."

it would be nice to find some solid numbers on this. as Conversly If you had BOV that could flow the CFM, having it in the middle could also seem ideal. as you would have pressure comming from the TB pushing back and, pressure comming from the compressor going forward, and Ideally having the BOV in the middle where the two presures meet up would theoretically combine that force out the BOV.. ::shrug:: just a concept I could totally be comming from left field.

Same problem as above - then you would need to repressurize half your intake after every shift.

I would put more effort in finding a BOV that works best at a desired boost level than placement of the BOV. As long as placement is within the norm that is...

Agreed.

I think I get what your saying. That if the bov Is next to the throttle body when it closes the air will simply divert out of the blow off valve rather then turning back to the turbo.

I understand that view but I don't think the air has that much mass. I don't thin it has the inertia to keep the pressure flowing out of the blow off valve. IMO the pressurized air would instantly push back threw tge compressor housing the instant there isn't enough flow/push on the turbine wheel to keep it turning normally.

I can understand both sides of this though. It's an interesting situation.

It doesn't need inertia - it has more air behind it, pushing it out the BOV. It often still backs up, sure, but it takes more than a couple seconds to surge through the cold pipe, intercooler, and hot pipe, and usually we're done with the BOV within a couple seconds.

see dumbo thats where I gotta disagree with you. I ran mine for 5 years, no problems. From 8-16psi (I'll credit that I can't vouche for Higher boost ranges) Never experianced flutter, high or low. And Like I said before, I'm a fan of the sound, so for me thats a +1. I've ran Blitz and Greddy's, and each one had aspects I wasn't a fan of. Again from before, If I were to get a "High-end" BOV it would by synaptics, but so far SSQV satisfies me.

Again, one person's success does not mean everyone will have similar results. The HKS flutter is well documented - it's even been admitted by HKS, after years of denial. Certainly, there are setups where it doesn't happen, however, a large percentage of them do this. My old HKS was prone to this. Nothing extreme, just light flutter at very low boost - I didn't worry about it because chances are it wasn't enough to cause any damage at a pound or two of boost.

 

[TurboStreetCar]

I see what your getting at. Keeping the air moving threw the system so it flows right out and keeps everything moving.

Admittedly I was only thinking of my car witch is automatic. When the throttle closes after boost it's usually followed by a period of 0% throttle while slowing down. Because of this I was thinking of a complete system drain not just a quick vent between shifts. I see the advantage to the placement now. Learn something new everyday.

 

[IJ.]

Always ran mine as close to the TB as I can so Air is always flowing >>>>

Modern turbos it's not so much of an issue as they usually have so much overhead capacity (which is why they surge to begin with) that they easily refill the entire volume if vented.

A nice quality BoV makes a difference.

 

[MA70Snowman]

Always ran mine as close to the TB as I can so Air is always flowing >>>>

Modern turbos it's not so much of an issue as they usually have so much overhead capacity (which is why they surge to begin with) that they easily refill the entire volume if vented.

A nice quality BoV makes a difference.

See we were so focued on when the TB was closed, we didn't think about it opening again lol. its like someone just turned a light on in my head. I wasn't questioning placement as close to TB makes sense. just theorizing out loud. ahhh.. well was fun. Thanks for taking your time to write that all out for us IJ