Forge BOV drivability issue

[bvass]

I just got my Forge BOV (recirculated) installed and I have a small issue. When I drive at part throttle and I accelarate (building 5+PSI of boost) as soon as I release the throttle a little bit the BOV opens wide and all the air gets dumped into the intake pipe. That causes my car to studder at that moment. I had a crushed 1G BOV before and didn't have that issue. The only change in the set up was the new Forge BOV. I currently run an EVO3 16G at 21PSI (mods in profile). The yellow spring is installed in the BOV. There are no problems at WOT. Boost builds fast, and gets released properly.

Why does this happen? Would switching to one of the other springs(blue, red) or adding shims help?

 

[1fastlaser]

its because it throws a weird signal to the maf sensor because of compressor surge. My evo does that with the stock turbo and the evo 9 metal bov. part throttle boost and let off it. You get alittle compressor surge and the maf gets funny. You eather need a lighter spring or tension, or give her alittle more gas

 

[bvass]

What throws a weird signal to the maf? The BOV? By "lighter" do you mean softer spring? The yellow one i got in is the softest i have.

 

[1fastlaser]

yeah lighter as in softer. Its compressor surge. If your in a low rpm under the boost threshold (like 2000rpms) getting it into 5-10psi and let out compressor surge will happen. Its because the motor isnt spinning fast enough to swallow the air the turbo is feeding it. The air backs up in the ic pipe track and when you let out it trys to spin the compressor wheel backwards if you didnt already know. My turbo sounds like its gonna explode when i do that, thats why i downshift hehe

 

[bvass]

It happens when I'm in low boost usually above 2500 rpm. I can hear the bov venting and my guage shows the pressure at 0 so I don't think that air gets back in ic pipes.

 

[1fastlaser]

It happens when I'm in low boost usually above 2500 rpm. I can hear the bov venting and my guage shows the pressure at 0 so I don't think that air gets back in ic pipes.

Thats my point, your not full throttle, so your throttle plate isnt fully opened and your turbo is trying to shove air in the motor when the throttle is 1/2 way open. The air starts to back up in the ic pipes, then when you let out the air rushes back to the compressor wheel and trys to spin it the opposite direction aka compressor surge...it makes the car feel like it stumbles

 

[mnetwork]

What I don't get is why the compressor surge makes the car stumble like that....

 

[bvass]

What I don't get is why the compressor surge makes the car stumble like that....

I think what 1fastlaser is saying is that when the air bounces back to the turbo trying to spool it backwards it causes the turbo to slow down fast and in turn the amount of air that gets trough the MAF decreases fast which makes the MAF act "funny". To me it feels exactly like fuel cut at that moment.

Can anyone with the Forge BOV running around 20PSI jump in? I want to know if I'm doing something wrong or if I need a new BOV.

 

[crimsondragon]

I'm not running 20 psi at the moment but I do have a Forge. It doesn't shudder for me when I release it at 5ish psi. I'm only running about 15 psi, spiking to 17 at the moment. I have the green spring, no shims. I would try going with the green spring and adding maybe 2 or 3 shims and see how it runs from there. Experiment with it a little.

 

[bvass]

I'm not running 20 psi at the moment but I do have a Forge. It doesn't shudder for me when I release it at 5ish psi. I'm only running about 15 psi, spiking to 17 at the moment. I have the green spring, no shims. I would try going with the green spring and adding maybe 2 or 3 shims and see how it runs from there. Experiment with it a little.

I hear you. My only problem is that I do not have the green spring. Just the three listed above, and I already have the softest (yellow) one in there. Thank you for the feedback. I will see if I can get my hands on a green spring.

Have you boost leak tested your set up? How much PSI can you hold with the green spring?

 

[crimsondragon]

I have never boost leak tested it. But I have one time set my EBC too high and I overboosted all the way to about 25 psi. Very bad, yes I know but kinda fun at the same time.

 

[Brutus]

I use the Forge recirculated BOV also and I have the yellow spring installed. I bought it because I tried two different crushed stock bov's and they both fluttered very bad at low boost.

I run 15 and 22 psi with a dual boost controller and the Forge BOV still flutters at low boost but not as bad. I dont have any dirvability issues with mine, but it does cause concern for the longevity of my turbo.

Does anyone think adding a couple shims would help?

 

[daren_p]

Have you boost leak tested your set up? How much PSI can you hold with the green spring?

I haven't had the Forge BOV for a few years now, but I believe the Green spring is the lightest? If so, I remember boost leak testing the lightest spring in the 20-22psi range & it held no problem.

 

[bvass]

I haven't had the Forge BOV for a few years now, but I believe the Green spring is the lightest? If so, I remember boost leak testing the lightest spring in the 20-22psi range & it held no problem.

The Green spring is the softest/lightest, but it is only rated up to 15psi - Forge Motorsport | Alloy Fabrication

Are you sure you had the green one installed? The yellow spring is the lightest I got in my kit. The green was not included.

 

[daren_p]

The Green spring is the softest/lightest, but it is only rated up to 15psi - Forge Motorsport | Alloy Fabrication

Are you sure you had the green one installed? The yellow spring is the lightest I got in my kit. The green was not included.

That rating from Forge isn't a specific "these springs are only good for this much boost" rating, they are just a general idea to help you have an idea of where to start from with spring choice. It was defently the green spring I tested to that range without any leaks

 

[welfle18]

I have a forge BOV 1st gen model and it leaks terribly at the base. Could be a boost leak.

 

[rich3389]

I have the yellow spring in my forge, it holds fine at 26 psi and still opens up with no flutter at low boost.

 

[blcknspo0ln]

I also have the stiffest spring with no issues. After Pat@Forge sent me the new snap ring, I can boost happy leak free

 

[bvass]

I also have the stiffest spring with no issues. After Pat@Forge sent me the new snap ring, I can boost happy leak free

I have the new version of the valve where the 2 holes do not go all the way to the top. Do I still need the new snap ring?

I haven't done a boost leak test after replacing the BOV, but my turbo spools pretty fast and vacuum stays at the normal level for my car so if I have a leak it will be a minor one.

Which spring do you use exactly? The stiffest is the red one in my kit.

 

[welfle18]

I am using the second softest in the kit I do believe. Mine leaks real bad. blcknspooln I sent you a pm to ask about this so I didn't clutter the thread.