BOV set up

[Spur]

How do you know when your BOV is set up right?

If it is set to light it will let off to much pressure causing lag while it rebuilds. If it's set to tight it will not dump pressure and cause back pressure problems.

It seems to me this would be a vital part of a good set up turbo system, and could make a huge difference in throttle response.

 

[robertyoke]

if it stays open it wont build boost at all or if it leaks till boost closes it, spool up will be slow or non existent. if it dosent open then turbo "bark" will occur, which is the air going back out the way it came in. that returning air will stop or even reverse the rotation of turbine blades which can break the shaft of the turbo.

 

[Why Not]

I think what he’s asking is how do you know if your valve is letting the precise amount of boost escape?

I have wondered about the same thing. I assume BOV’s can be adjusted or do you buy them set up to allow different amounts of boost to escape? This may be different for every sled, or at least would have to be set just right to obtain spot on response. Are all BOV’s set to the same pressure release? Do the kit builders have this figured out for their kits and order the valves from the factory at a certain release setting?

Just for example:

Let’s say you’re running 18 pds of boost. You let off the throttle and the valve dumps all the boost above 4 pds. When you grab the throttle again the system has to rebuild boost from 4 pds of pressure. I’ve always assumed this was turbo lag. What if you’re set up could maintain 8 pds of boost without forcing boost back into the turbo or have any negative effect on your system. This would mean when you grabbed the throttle your system only has to build from 8 pds to whatever instead of 4 pds which would give you less lag and better throttle response right? How do you know your valve is set to dump all but 8 pds of boost? How do you know how much boost your set up can handle without the negative effects of no boost release?

 

[powderlites]

Blowoff valve setup.

I will take a shot at answering this as I get a lot of calls on blowoff valves.
I want blowoff valve open at about 6 inches vaccum.
So if your turbo setup has 7inches vaccum your blowoff valve is wide open at idle. Lots of guys saying my blowoff valve is leaking thinking there is a problem.
I want on my boosted motors to have it open at idle so turbo is spooling up and lets say is spinning at 20,000 RPM without any pressure on throttle bodies.
If you have no blowoff valve and turbo at idle is spinning at 5000 RPM which kit will have lag?
The moment you snap the throttle on a proper blowoff valve turbo the spring closes and gives you boost.
Then boost keeps valve closed no matter how much boost you have.
All this grap about high pressure springs and valves is just that.
Hope this helps and it's only my opinion if someone tells you I am wrong then he has been sucked into buying some junk without knowing how it works.
I get so many guys telling me our blowoff valve leaks on our kit setup that this should stop a few calls and emails.
Think about it and you will get it. Snap that throttle open and see what happens in a drag race against our rear mount Nytro.!
www.powderlites.com

 

[Linc]

I have seen so many BOV's set with the stiffest spring it's unreal, if it's too stiff then the BOV closes before the boost pressure has been disapated, then it stalls the turbo and that helps create lag, it is also not good for the turbo. I agree with Dave on BOV set up, I've fixed many BOV's and the performance is much improved with a light spring set up, I set mine up with the BOV slightly open or fluttering at idle.

 

[MTdream]

how much heat is generated by continuing to spool the turbo? is it nominal? or minimal?

also, is there a difference for where the turbo is mounted? mid? rear? or is the effect the same?

yes, I get the logic, quicker spool, but just curious if it is a bigger impact for different mount locations and if it increase heat etc.

thanks

 

[Linc]

The hotter the turbo stays, the quicker the spool up, it's one of the reason the rear mount has more lag than front mounts, the exhaust pipe cools down and the spool is lost till it heats up again, many people find that wrapping the header pipe to the turbo increase spool up.

 

[gunnerthesnowman]

Trying a standalone fuel system , it has a anti turbo lag setting , keeps the turbo hot and spooled up .

The hotter the turbo stays, the quicker the spool up, it's one of the reason the rear mount has more lag than front mounts, the exhaust pipe cools down and the spool is lost till it heats up again, many people find that wrapping the header pipe to the turbo increase spool up.

 

[redbull660]

This is some good info, I have a NW Turbo Works setup on my nytro and have noticed that the throttle response is bad. They did tell me that the spring may be to stiff and it may have to be cut shorter or replaced with a softer spring. I guess I am going to try it. thanks for the info, keep it coming.

 

[redbull660]

How about this, does anyone make an adjustable blow off valve, if there is such a thing wouldn't that be easier??????????

 

[Linc]

Trying a standalone fuel system , it has a anti turbo lag setting , keeps the turbo hot and spooled up .

Mitch from the Synergy fame used to and probably still does play with car turbo systems, and one of the things he used to use for launching at full boost was to set up the ignition and fuel to stutter at a lower rev limit, which would build heat and boost, as soon as the boost was ready,,, hang on.

This is the same thing you see in the rally cars, that popping noise you hear at the start when they're at near full revs just sitting there waiting for the clock to go.

I've always said that the outfit that can make a closed loop system will be the winner in this turbo war, I've been keeping an eye on your posts about this system, sounds good so far.

 

[gunnerthesnowman]

Have not heared from Mitch in a long time , but he was the one that started most of us trying new and better fuel systems , hope to get out riding with him again this year .
I will post some video of dyno testing and frist trip out with this system .
Gunner

Mitch from the Synergy fame used to and probably still does play with car turbo systems, and one of the things he used to use for launching at full boost was to set up the ignition and fuel to stutter at a lower rev limit, which would build heat and boost, as soon as the boost was ready,,, hang on.

This is the same thing you see in the rally cars, that popping noise you hear at the start when they're at near full revs just sitting there waiting for the clock to go.

I've always said that the outfit that can make a closed loop system will be the winner in this turbo war, I've been keeping an eye on your posts about this system, sounds good so far.

 

[mattymac]

If an intake already has vacuum at idle then the turbo is freespooling already!


Lota variables here with sled/motor, intake size, exhaust, turbo size, etc. but there isnt "boost at idle"

 

[Linc]

Only if the BOV is open, otherwise it's pushing against the throttle plates and stalling the turbo. If the spring tension is higher than the vacume, then even the smallest throttle movement won't effect the BOV and that's when you need the most. If high vacume is only thing that will move the BOV, then what happens at low vacume. Nothing, and this is when the engine is most sensitive to turbo stall or turbo lag.

 

[redbull660]

Mine idles at about 6 pounds of vaccuum, what does this mean???

 

[Linc]

That means that your BOV should be open slightly. It's all relative, if your rig pulls 6 inches vacume or 12 inches it doesn't matter, your BOV should be on the edge of opening, or just barely open.

 

[JOP]

I have the B.D. Alpine set up with a Gt 25 turbo on an 06 Vector. My blow off valve sping is cut down 3/8th of an inch from stock length and The Turbo wisslllllllllsssss at start up. Seems to build boost right off the get go with little to No Lag. I just bought the sled so I have very little time/knowlege about the setup. Trying to learn more, Hope this helps alittle.

 

[Spur]

I will take a shot at answering this as I get a lot of calls on blowoff valves.
I want blowoff valve open at about 6 inches vaccum.
So if your turbo setup has 7inches vaccum your blowoff valve is wide open at idle. Lots of guys saying my blowoff valve is leaking thinking there is a problem.
I want on my boosted motors to have it open at idle so turbo is spooling up and lets say is spinning at 20,000 RPM without any pressure on throttle bodies.
If you have no blowoff valve and turbo at idle is spinning at 5000 RPM which kit will have lag?
The moment you snap the throttle on a proper blowoff valve turbo the spring closes and gives you boost.
Then boost keeps valve closed no matter how much boost you have.
All this grap about high pressure springs and valves is just that.
Hope this helps and it's only my opinion if someone tells you I am wrong then he has been sucked into buying some junk without knowing how it works.
I get so many guys telling me our blowoff valve leaks on our kit setup that this should stop a few calls and emails.
Think about it and you will get it. Snap that throttle open and see what happens in a drag race against our rear mount Nytro.!
www.powderlites.com

Dave & Linc, Thanks for getting me straight on this. I had the wrong idea of how the BOV actually works. After reading your posts I got it. Here's to you , along with a rep.

Spur