[john boxter]

hey guys can someone please either point me in the right direction or explain to me how a bov works so if i get a tial bov with the 11lb spring once it hits 11 lbs it blows? that cant be right or you cant build boost so what does the wieght signify in the spring?

[solid77]

i could be wrong, but from what i gather:

the spring isn't for max boost, it's for deceleration where u get high vacuum loads, so it doesn't suck in unfiltered air. so you put in the lightest spring possible to achieve this.

[ToadHollow]

If you have (or go with a tune) get the upgraded DVs before the BOV. I had my OEM dv swapped out for the Riss Racing dvs & I'm surprised at how much better (and needed!) the car performs. The boost doesn't taper off as dramatically as it had with the OEM dvs ...........

Just sayin' .........

[Terrance28]

I will find a article of how a BOV works, I posted it on the boards already I will search and paste it here.

[jhershorin]

On the Tial you want to run the q11. It is backwards from what you would expect. Essentially you want to make sure that the BOV opens under the right conditions and using the lighter springs will cause issues.

[Terrance28]

Here you go

My bov stays open also on idle but it doesn't suck air in rather blow out. Here just read this it will explain alot on how a bov works. Springs don't close the bov high vaccum and boost does.

The Blow Off Valve (BOV) is one of the most misunderstood products in the automotive aftermarket. The goal of this article is to clear up some of the common myths about BOVs and explain how blow off valves really work and how to adjust them properly. Please read this article in its entirety prior to installation of any aftermarket BOV; your turbochargers life may depend on it!

As you know, the purpose of a BOV is to make that cool "PSSSSHHHH" sound when you let off the accelerator. The secondary purpose is to prevent waves of high pressure from slamming into the compressor wheel on your turbo when your throttle plate slams shut, extending turbo longevity.

BOV Myth #1: The adjustment screw on top of an aftermarket BOV adjusts the sound that the BOV makes.

This is the most dangerous myth of all. If you hear a different sound from adjusting this screw, it means you are getting compressor surge which could destroy your turbo.


All this screw does is adjust the preload on your BOV spring. BOV's have a small metal plate on top of the spring. The screw screws directly into this plate, compressing the spring. Tightening it (turning it right/in) will compress the spring, increasing the spring energy. Loosening it (turning it left/out) will decompress the spring, lowering the spring energy. (Side note: you can achieve the exact same effect by placing washers/shims on top of the BOV spring.) As you will read below, the BOV spring should be adjusted to the lightest level possible while still holding your BOV shut during high vacuum conditions.

BOV Myth #2: The spring in a BOV holds the BOV closed during moments of high boost.


First thing is first: The purpose of the spring in a BOV IS NOT to hold your BOV closed under boost pressure! Selecting a spring based on PSI is incredibly confusing/meaningless and it makes us wonder if the people who pioneered aftermarket BOV design in the first place even understood how they work.

All BOVs have a reference line coming into the top of the BOV from your post-throttle body intake manifold. Under high boost, the force holding the BOV closed is BOOST! The pressure coming through the reference line is equal to the pressure under the BOV piston. Therefore a VERY mild spring will hold it shut just fine under these conditions.

Rather, the purpose of the spring in a BOV is to hold the BOV closed when your throttle plate is closed, IE during idle and deceleration conditions. Under these conditions, the vacuum in your intake manifold is much higher than the vacuum in your intake piping (therefore under the BOV piston) so the BOV has a natural tendency to spring open. Being open isn't even a problem if you are recirculating your BOV into your intake, however if you are NOT recirculating, it can allow unfiltered air into your intake which IS a problem.

Therefore, your goal when selecting a BOV spring and adjusting the BOV should NOT be to select a spring based on your boost level; that makes no sense. Your goal is to get the BOV to stay CLOSED during high intake manifold vacuum/closed throttle plate conditions, using the very smallest amount of spring energy possible. Using less spring energy will allow the BOV to snap open as rapidly as possible when pressure release is necessary

Have a friend just touch or push the gas pedal and you look at the bov piston it will shut, now if you are under boost or high vaccum it will stay shut. According to this article choosing a spring based on vacuum idle like Tial wants is ridiculous. The BOV works becuase of the vacuum line that is mounted to the BOV. You want the lightest spring possible in a BOV but enough to close the BOV at high vacuum if you have a BOV that opens at idle. If you have a BOV that is normally closed at idle then you would just want the lightest spring possible. High vacuum and boost in the line is what shut and keeps a BOV shut.

The section I highlighted is not an issue with our cars. Our turbos are so efficient that when the BOV is open at idle it blows air out not suck it in. That statement is directed more to other cars not ours.

[john boxter]

i dont understand how a lighter spring is better but you complained of compresser surge with the tial bov and the lightest spring correct?

[Terrance28]

A lighter spring will allow the BOV to snap open easier than a heavier spring. I had the white springs in my BOV don't know if it was the lightest.

[john boxter]

was it the ones that came with it?

[Terrance28]

Yes its the one it came with.

[john boxter]

oh man that sucks was really looking forward to that one maybe ill just go dv's then

[XPO186]

Originally Posted by Terrance28

Here you go

My bov stays open also on idle but it doesn't suck air in rather blow out. Here just read this it will explain alot on how a bov works. Springs don't close the bov high vaccum and boost does.

The Blow Off Valve (BOV) is one of the most misunderstood products in the automotive aftermarket. The goal of this article is to clear up some of the common myths about BOVs and explain how blow off valves really work and how to adjust them properly. Please read this article in its entirety prior to installation of any aftermarket BOV; your turbochargers life may depend on it!

As you know, the purpose of a BOV is to make that cool "PSSSSHHHH" sound when you let off the accelerator. The secondary purpose is to prevent waves of high pressure from slamming into the compressor wheel on your turbo when your throttle plate slams shut, extending turbo longevity.

BOV Myth #1: The adjustment screw on top of an aftermarket BOV adjusts the sound that the BOV makes.

This is the most dangerous myth of all. If you hear a different sound from adjusting this screw, it means you are getting compressor surge which could destroy your turbo.


All this screw does is adjust the preload on your BOV spring. BOV's have a small metal plate on top of the spring. The screw screws directly into this plate, compressing the spring. Tightening it (turning it right/in) will compress the spring, increasing the spring energy. Loosening it (turning it left/out) will decompress the spring, lowering the spring energy. (Side note: you can achieve the exact same effect by placing washers/shims on top of the BOV spring.) As you will read below, the BOV spring should be adjusted to the lightest level possible while still holding your BOV shut during high vacuum conditions.

BOV Myth #2: The spring in a BOV holds the BOV closed during moments of high boost.

First thing is first: The purpose of the spring in a BOV IS NOT to hold your BOV closed under boost pressure! Selecting a spring based on PSI is incredibly confusing/meaningless and it makes us wonder if the people who pioneered aftermarket BOV design in the first place even understood how they work.

All BOVs have a reference line coming into the top of the BOV from your post-throttle body intake manifold. Under high boost, the force holding the BOV closed is BOOST! The pressure coming through the reference line is equal to the pressure under the BOV piston. Therefore a VERY mild spring will hold it shut just fine under these conditions.

Rather, the purpose of the spring in a BOV is to hold the BOV closed when your throttle plate is closed, IE during idle and deceleration conditions. Under these conditions, the vacuum in your intake manifold is much higher than the vacuum in your intake piping (therefore under the BOV piston) so the BOV has a natural tendency to spring open. Being open isn't even a problem if you are recirculating your BOV into your intake, however if you are NOT recirculating, it can allow unfiltered air into your intake which IS a problem.

Therefore, your goal when selecting a BOV spring and adjusting the BOV should NOT be to select a spring based on your boost level; that makes no sense. Your goal is to get the BOV to stay CLOSED during high intake manifold vacuum/closed throttle plate conditions, using the very smallest amount of spring energy possible. Using less spring energy will allow the BOV to snap open as rapidly as possible when pressure release is necessary

Have a friend just touch or push the gas pedal and you look at the bov piston it will shut, now if you are under boost or high vaccum it will stay shut. According to this article choosing a spring based on vacuum idle like Tial wants is ridiculous. The BOV works becuase of the vacuum line that is mounted to the BOV. You want the lightest spring possible in a BOV but enough to close the BOV at high vacuum if you have a BOV that opens at idle. If you have a BOV that is normally closed at idle then you would just want the lightest spring possible. High vacuum and boost in the line is what shut and keeps a BOV shut.

The section I highlighted is not an issue with our cars. Our turbos are so efficient that when the BOV is open at idle it blows air out not suck it in. That statement is directed more to other cars not ours.

Tial's recommendation for selecting spring pressure based on idle vacuum is explained perfectly by this article. How is that a ridiculous thing?

1. The 11lb spring = ~22 in/Hg and the 9lb (aka white spring) = ~18 in/Hg
Since our cars idle at -20 in/Hg, The valve is closed at idle with the 11lb spring, and open with the 9lb spring. Closed at idle is recommended by the article, however it should not matter since the chargepipe never sees vacuum and will always blow air out even if the valve is open.

2. During deceleration (braking in gear) and at throttle closure (between shifts), manifold vacuum jumps to ~23-24 in/Hg. Go ahead and check this on your boost gauge. This means that there is greater vacuum at those points than at idle and easily overcomes the BOV's spring rating (either the 9lb or 11lb spring). What this implies too is that the lighter spring will be lazy to close (and therefore less responsive) since its natural tendency is to be open.

3. The big difference is in response. In one situation, the valve is already closed and therefore you are able to build boost instantly. On the other hand, if the valve sits open, manifold pressure must go from vacuum to positive pressure in order close the valve and hold it closed. It may seem like an insignificant amount of time but I can confirm it: THERE IS A SLIGHT LAG IN BOOST RESPONSE WHEN THIS OCCURS. I challenge anyone with a Tial BOV to try both an 11lb spring and 9lb spring back to back and tell me the 9lb spring was "more responsive" than the appropriately rated 11lb spring (trust me, it won't be). Most people may not even care about that slight lag, but it bugged the crap out of me everytime I drove the car. My theory is that positive pressure in the chargepipe makes the valve hang open for just a split second before manifold pressure becomes positive and THEN shuts the BOV.

Originally Posted by Terrance28

A lighter spring will allow the BOV to snap open easier than a heavier spring. I had the white springs in my BOV don't know if it was the lightest.

That's true, and it probably won't hurt anything. However, if you follow the recommendations of the article the white/9lb spring is not what you want to use and Tial even recomends a different spring for our engines. Also, the 11lb spring opens up just as easily at exactly the times you want it to -- between shifts.

Actually, the lightest spring they offer is 3lb... for supercharger applications.

[Terrance28]

I had the white springs in my Tial and according to you those are the 9lb springs and my BOV stayed shut at idle, and it still fluttered sometimes. With my synapse it stays open while idle but it closes so instantly on any touch of the pedal their is no lag whatsoever actually my response has never been better. Maybe calling their vacuum chart ridiculous was a little over the top. I guess it was just my tial that had that issue but I didn't like it at all, didn't want to bother to change out the springs to see if it would help because I didn't like how quiet it was anyway.