BOV Setup for your N54

[doublespaces]

I'll be installing the plain spring tonight. That is the spring tial calls for with my 20in of engine vacuum and a 1/4 signal.

See how it goes.

Yes, but does your car show 20in/hg with the ac on and immediately after you let off the throttle? The drive by wire usually holds it open slightly causing you to not see full vacuum for a brief moment. I tend to find that our cars operate better with a lighter spring.

When I'm driving warmed up and decelerating, I show 10.5 PSI of vacuum which is over 21 inches. I run the black spring and my bov actuates fantastic and very quickly.

 

[foe516]

good write up. thanks

 

[Bmwfixerguy1]

Yes, but does your car show 20in/hg with the ac on and immediately after you let off the throttle? The drive by wire usually holds it open slightly causing you to not see full vacuum for a brief moment. I tend to find that our cars operate better with a lighter spring.

When I'm driving warmed up and decelerating, I show 10.5 PSI of vacuum which is over 21 inches. I run the black spring and my bov actuates fantastic and very quickly.

I'll be honest I didn't give that thought.. it's heavier that what I have in there now but lighter than what I had before that.. so I guess we will see is really what it comes down to.. I felt I playing a little safter than others as well lol

 

[Chris@VargasTurboTech]

Fixed broken links!

 

[Maniac0908]

Is the black spring ideal for single turbos as well?

 

[Payam@BMS]

Is the black spring ideal for single turbos as well?

I don't like it, too much flutter. I cut mine and took one coil off. Or you can just get a 6 psi spring.

 

[Maniac0908]

I don't like it, too much flutter. I cut mine and took one coil off. Or you can just get a 6 psi spring.

Isn’t the black one 6 psi?

 

[fmorelli]

I don't like it, too much flutter. I cut mine and took one coil off. Or you can just get a 6 psi spring.

I think @matreyia went with the white spring ~8psi ... the way I read Greg @ Tial say it, the valve should be just closed but ready to open lol ...

Filippo

 

[Payam@BMS]

Isn’t the black one 6 psi?

I'm not sure, I forgot the colors

 

[Payam@BMS]

I think @matreyia went with the white spring ~8psi ... the way I read Greg @ Tial say it, the valve should be just closed but ready to open lol ...

Filippo

Mines open at idle.

 

[Jeffman]

I have the white spring (8 psi) and my TIAL BOV is open at idle. Black spring is 6 psi.

 

[NoQuarter]

Why do we not have adjustable springs on these things? Put in a spring... turn the locking screw up/down to fine tune it.

 

[fmorelli]

Why do we not have adjustable springs on these things? Put in a spring... turn the locking screw up/down to fine tune it.

Are you looking for another project?

Filippo

 

[Jeffman]

Here is another scenario that I think I'm experiencing all due to not having a trial set up correctly..
So I'm running a tial but with out a 1/4 signal like it demands.. I just havnt had the time.. So to reduce surge and delay I went with a lighter spring.. So now the BOV is open at idle.
Fast forward a few months and I'm noticing really really inconsistent boost targeting.. New solenoids,thought I fixed it. Nope.
Re ran all my vacuum lines to fix a couple that were kinda collapsed. Nope.
Check for boost leaks as in nut and bolted all connections. Nope.
I'm almost willing to bet that the lighter spring is being over come by boost.. Havnt proved it yet but something is telling me that's what's up. With out the 1/4 signal pascals law can't play into affect with exerting the force equally against the valve from manifold pressure
This may be debunked as soon as I post it but I feel I'm on to something lol

You may be on to something. (Reviving old, but important, thread)

I switched from Forge Diverter Valves with pretty strong springs (yellow iirc) to TIAL-Q with the white 8 psi spring. I’m on stock turbos that had achieved 23-24 psi with Forge DV but now only reach 18-20 psi with TIAL-Q / 8psi white. My TIAL-Q is slightly open while idling.
I completely understand that at static equilibrium, boost pressures in the manifold and charge pipe will even out so any spring will keep the BOV closed. But our cars rarely are at static equilibrium and are constantly (dynamically) changing, especially under spool conditions. So I can imagine stock turbos quickly spooling, thereby quickly building pressure. Simultaneously the throttle is wide open and the engine is gulping all the air as fast as it can from the manifold. So at that initial point (like within the first second of spool up) it seems possible to me that there can be a momentary pressure differential between the manifold and the charge pipe (charge pipe having higher pressure than the manifold). So if this momentary pressure differential is greater than the spring pressure, then the spring will be unable to close all the way and air may leak out of the BOV, thereby manifesting itself as a boost leak.

This may explain my sudden reduction in boost pressures when I switched to the TIAL-Q.

I have a yellow 11 psi spring and also just purchased a plain 10 psi spring for testing purposes.

 

[Torgus]

You may be in to something. (Reviving old, but important, thread)

I switched from Forge Diverter Valves with pretty strong springs (yellow iirc) to TIAL-Q with the white 8 psi spring. I’m on stock turbos that had achieved 23-24 psi with Forge DV but now only reach 18-20 psi with TIAL-Q / 8psi white. My TIAL-Q is slightly open while idling.
I completely understand that at static equilibrium, boost pressures in the manifold and charge pipe will even out so any spring will keep the BOV closed. But our cars rarely are at static equilibrium and are constantly (dynamically) changing, especially under spool conditions. So I can imagine stock turbos quickly spooling, thereby quickly building pressure. Simultaneously the throttle is wide open and the engine is gulping all the air as fast as it can from the manifold. So at that initial point (like within the first second of spool up) it seems possible to me that there can be a momentary pressure differential between the manifold and the charge pipe (charge pipe having higher pressure than the manifold). So if this momentary pressure differential is greater than the spring pressure, then the spring will be unable to close all the way and air may leak out of the BOV, thereby manifesting itself as a boost leak.

This may explain my sudden reduction in boost pressures when I switched to the TIAL-Q.

I have a yellow 11 psi spring and also just purchased a plain 10 psi spring for testing purposes.

I would recommend you keep your BOV closed at idle. There is no reason to suck in unfiltered air into your engine if you don't have to. Luckily we don't have a MAF but if we did it would not run/idle correctly because of the unmetered air. The only time a BOV will be open at idle is with a SC as there is positive pressure in the IM. Tial makes springs just for this application.

If you have a quick spooling turbo, like our tiny stockers, it can actually push the valve open briefly before the charge gets to the maniforld; dumping boost. According to Tial. Now I don't think this is what is happening to you but I thought I would mention it.

Tial spells out very clearly which spring to use based on the vacuum at idle your engine produces: http://tialsport.com/documents/w3_tial_qqr_sp.pdf & http://tialsport.com/documents/BOV Static Testing.pdf You REALLY want to have a 1/4" inner diameter DIRECT source to the manifold. A smaller line or one T'd off for a boost reference or gauge is going to slow the response of the BOV which you do not want for obvious reasons.

If you were making 24PSI peak on DVs and now can only make 20PSI peak with the Tial BOV on the exact same tune and no other variables changed, I would guess you have a boost leak. What do your logs look like before and after? I suggest you take the tial off and check the o ring gasket. You can pinch it when you do the install easily enough. Might as well do this when you put the correct spring in based on your engine vac so the BOV is shut at idle. You also changed the CP I am guessing so check those connections. You could also smoke test/boost leak check the intake path for small money.

Best of luck!

 

[doublespaces]

I would recommend you keep your BOV closed at idle. There is no reason to suck in unfiltered air into your engine if you don't have to. Luckily we don't have a MAF but if we did it would not run/idle correctly because of the unmetered air. The only time a BOV will be open at idle is with a SC as there is positive pressure in the IM. Tial makes springs just for this application.

Can you explain how positive pressure in the intake manifold would open a bov at idle? Most of what you just said is irrelevant or doesn't make much sense.

If you put 20 psi into the intake manifold at idle as an example, you'd have 20 psi pushing down on the blow off valve diaphragm in addition to the bov spring itself. Please explain how it would open up?

This is what you are suggesting assuming an 8 psi bov spring and you can substitute 20 psi with any boost figure:

 

[Torgus]

Can you explain how positive pressure in the intake manifold would open a bov at idle? Most of what you just said is irrelevant or doesn't make much sense.

If you put 20 psi into the intake manifold at idle as an example, you'd have 20 psi pushing down on the blow of valve diaphram in addition to the bov spring itself. Please explain how it would open up?

This has basically nothing to do with our platform but I am happy to indulge:

http://tialsport.com/documents/TiAL%20FAQ-BOV%20Product.pdf

3. Why is there a unique spring pack for supercharged applications? Supercharged engines typically produce positive manifold pressure at idle and most supercharger manufacturers recommend bypassing that pressure for tuning purposes. As a result we suggest a very weak spring to allow the valve to remain open at idle, but to close very rapidly once that negative pressure is increased to positive. It is perfectly normal for our BOV to be open at idle on supercharged applications.

Since your supercharger's airflow is directly related to your engine's rpm it's is only going to be closed only under load when positive manifold pressure is desired. On a SC they are often called bypass valves vs. turbo applications they are called blow off valves or diverter valves. Both serve the same function which is preventing compressor surge.

What was irrelevant or does not make sense to you that I wrote? I apologize, tried to be succinct as possible.


What @Jeffman really needs to figure out is why he is making less peak boost switching from DVs to a BOV and get his BOV closed at idle.

 

[doublespaces]

http://tialsport.com/documents/TiAL%20FAQ-BOV%20Product.pdf

3. Why is there a unique spring pack for supercharged applications? Supercharged engines typically produce positive manifold pressure at idle and most supercharger manufacturers recommend bypassing that pressure for tuning purposes. As a result we suggest a very weak spring to allow the valve to remain open at idle, but to close very rapidly once that negative pressure is increased to positive. It is perfectly normal for our BOV to be open at idle on supercharged applications.

What was irrelevant or does not make sense to you that I wrote?

I didn't see your supercharger comment. Have you measured airflow at the bov on stock turbos at idle?

 

[Torgus]

I didn't see your supercharger comment. Have you measured airflow at the bov on stock turbos at idle?

Oh yeah nothing to do with turbos, I just mentioned it as there is a time when you BOV should be open at idle but it is not on a turbo car!

Do you mean measure vacuum at idle to determine which spring I should run? Twins or a single it should not change the vacuum the engine pulls at idle afaik. I have not measured to be honest and I have everything to measure it in the garage.

I would measure if the Tial BOV did not perform flawlessly with the spring I 1st put in it years ago. I honestly don't even remember which spring I run. Most N54s should draw the same vacuum at idle IIRC on a warm n54 you should see around 16-18 in/hg? With the 1/4'' ID line from the IM and that my BOV stays closed at idle and instantly opens the second I lift my foot I can't complain and have no reason to think a spring change would help me in any way. If anything it would either be too stiff or let the BOV be open and let in unmetered air.

 

[Jeffman]

What @Jeffman really needs to figure out is why he is making less peak boost switching from DVs to a BOV and get his BOV closed at idle.

Exactly. Thanks for your comments. Pretty sure my install was pinch-feee, but I’ll double check everything and test the stronger springs.