ok so i made a stupid mistake and traded my aps twin vent for a gfb stealth.
anyway this thread is for anyone out there considering buying this crap bov.
it flutters badly regardless of adjustments at 4k in 16-18 lbs.
also has minor compressor surge regardless of adjustment at around 3-4 lbs.
i spent about 2 hrs trying to adjust this valve to stop either or both problems with no luck.
two thumbs down and one of the worst bovs ive ever had. on the positive side it sounds good lol.
i miss my aps twin vent. just like stock no problems at all

 

I had a stealth fx too got rid of it for a jdm ix diverter. Best move I did.

 

Wow...never had a single problem with mine. Best BOV i've ever used. Are you sure you were adjusting it properly? Mine works flawlessly. But, i also know how to set it up. It can be difficult and takes time.

 

Hi adcgn45,
Sorry to hear about the issues you’re having with your Stealth FX. I spoke to our engineer, Brett, who tells me that since your original post, he’s been working with you to solve the problem.

I was just wondering if you had received the spring that he sent, and had any luck sorting out the issues? He indicated that some adjustments you had since made did help to a certain extent, so I just wanted to follow up to see how it’s going.

Likewise, evyevolution8, if you still have your Stealth FX and would like some help with it, please let me know if there’s anything I can do, or if you can share the details about the issues you had, I'd like to hear it.

iTune, thanks for your positive comment, glad to hear your Stealth FX is working well for you. The EVOs can be a little trickier than most to set up, and the trick is achieving the correct balance of spring pre-load and atmosphere venting. The extra adjustment of atmosphere bias does complicate setup, but in reality it is by far the best way to achieve atmosphere venting on a car that runs an airflow meter.

Best regards,
GFB Pete

 

No problem. I'm a former dyno tuner with many years of experience and i can honestly say that the GFB Stealth FX BOV is one of the best built BOV's I've ever used(i've used just about every BOV on tons of setups). It's always worked flawlessly. Because of it's adjustability, it does take a little longer to dial in correctly. But, well worth it.

Brett is great too BTW! I recently asked him some questions regarding my StealthFX BOV and you guys sent me a rebuild kit asap, free of charge. I'm going to freshen my o-rings up, as they have gotten a little dry-rotted over the 5 years my BOV has been in service. The BOV still works flawlessly though, so this is just me being ****. O-rings don't last forever, as they are made of rubber and WILL dry-rot over a period of time. This has NOTHING to do with the BOV's construction, which is still perfect, even after 5 years of hard service.

What i like the most about the GFB BOV's, beyond their quality, craftsmanship and adjustability is the design. The piston design and the fact that the piston itself does not use a o-ring, but rather an actual piston ring, sold me on the design. Other manufacturers don't do this.

Keep up the great work guys! I will continue to use your StealthFX, in kill mode, on my 480whp EVO VIII. And for everybody else, i have and will continue to recommend this BOV!

 

my stealth fx actually leaks out the top chrome coloured part, opened it up to try fix it but can't access it, then the bloody spring and ball flew out and couldn't get it back in, now the adjustment doesn't "click" and I still have the leak out the top part...

 

WOW, nothing but goods words from me on my Stealth. Worked fantastic

 

There are o-rings in that top that can be replaced. GFB should be able to help you.

 

had a forge rs, and traded for the gfb bov and was unable to set it properly and fluttered at almost every amt of boost with what i think was every adjustment possible so i just said screw it and went back to the forge rs.. soo much easier and hardly ever flutters, only maybe on partial throttle

 

Hi everyone,
Thanks for all the comments! We love to hear feedback - if it's good, great, if it's bad, better we know and can do something about it!

First, a note on leaks. Sorry for the heavy tech that is about to follow! The following link is an article that we wrote on BOV leaks because it is a very common topic that comes up:

http://racedotcom.com/showthread.php?t=27447

This next link is an article on leak testing methods, because the most common methods used will often show a leak, but do not tell you whether or not the leak is the cause of an issue you might be tracing:

http://racedotcom.com/showthread.php?t=27434

Even though we don't like to find leaks, I will go on record by saying that yes, if a leak show up in your BOV it makes sense to fix it - that's plainly obvious to anyone! However, the important point to note about a GFB valve is that if it vents when you shift gears, it's about 99.9% certain that any leak shown by a leak test on that valve is not large enough to cause a boost pressure or performance loss. In fact, such a leak would be the same or significantly less than the amount of air leaked by a boost control solenoid.

This is because even with all the seals in a GFB valve removed, the tolerances between the components simply will not allow more than a tiny amount of air to leak past. Sure, a leak test in this case will show bubbles or smoke, but the amount of air would literally be in the order of thousandths of a percent of the air consumed by the engine, and completely undetectable by the ECU.

The only way a GFB valve can leak enough air to cause a boost pressure drop, performance loss or change in air/fuel ratio, would be for the piston to open under boost. The great news is, physics will tell us that the only condition that can cause this to occur also prevents the valve from venting during a gearshift. Hence my original comment that if the valve vents during a gearshift, it is highly unlikely it will open under boost and cause a boost pressure or performance loss.

Ok, with that out of the way, Burnzy, I believe I can help you. As you've discovered(!), the Stealth FX needs to be disassembled in a specific order to prevent the ball and spring from flying out (and so you can re-assemble it with the ball and spring). If you email our engineer, Brett, (brett@gfb.com.au) he can shoot you over the instructions to do so, and also tackle the leak at the top of the valve at the same time.

Itchy, in regards to your concerns about the fluttering, it's most common for it to occur when lifting off at low RPM/high load (which I will address below). If flutter occurred when lifting off from high RPM and boost, there may have been an issue that needed to be looked at, which I can help you with if you're interested in giving it another shot.

On the topic of flutter, the reason the Stealth FX is a little more fiddly than others to set up is because venting to atmoshere requires a very different spring pre-load than recirculating. When the valve is recirculated, the spring can be made soft enough that the valve opens at idle (the factory valve does this, at least partially). This means the valve opens more readily and therefore prevents the low RPM flutter with little or no need for adjustment.

However, if you were to take a recirc valve and try to vent to atmosphere, the car would simply stall, because the valve is open at idle and will mess up the A/F ratio. In order to sucessfully vent to atmosphere, the valve must close at idle to prevent stalling. This needs a firmer spring rate to achieve, which means the valve is closer to the fluttering threshold, and therefore more likely to flutter, particularly at low RPM. Softening the spring to its softest setting will help reduce this, and there are some other things to try.

I will also put my neck on the line by saying that if flutter occurs when lifting off at any point prior to the turbo reaching full boost, its effect on the turbo are pretty negligible.

Now, the other interesting thing is that the firmer spring pre-load of the atmosphere venting valve can actually help reduce lag during high RPM shifts. This is because a firmer spring pre-load can hold a small amount of pressure in the intercooler pipes during a shift, whereas a softer spring in a recirc valve will have let out all of the pressure by the time you grab the next gear. This effect can be seen in the following articles:

http://racedotcom.com/showthread.php?t=27445

http://racedotcom.com/showthread.php?t=27446

This is why tuning the valve can be tricky - you need to strike a balance between the flutter, the ECU (if venting to atmosphere), and best throttle response. In some cases, it's possible that no single spring pre-load setting meets all three requirements, hence a valve set up for best throttle response at high RPM might tend to flutter more at low RPM, or a valve set up to eliminate all flutter might cause idle problems or not have the best throttle response. If a recirculating valve is used, and it is designed as a "blanket" solution to prevent flutter (as the factory valve is), it's very likely it achieves this at the expense of throttle response and lag.

The great thing about the Stealth however is the ability to adjust these features to suit different preferences.

Sorry again for the huge post, but I hope I've answered some questions (and probably created a few more)!

Best regards,
GFB Pete

 

Thanks pete, if I can get this fixed this bov would rate amongst the best I have used! I'm running 2 bar of boost and it seems to be holding up fine, just the leak is bugging me as it goes away when i push the chrome part in. Other problem is now the adjustment goes off as my ball and spring is gone but you said brett can help me with that, all good
Will report back how I go.

 

I've had mine for almost 3 years now with no issues. I guess I just got lucky when I got mine. Just threw it on, adjusting it only took about 10 min and its been golden ever since.

 

bumping this, I need all the help I can get b/c my bov is both surging (jerking) when letting off slowly in high speeds or in boost and fluttering as well midway through the rpm range. The bov is being recirculated fyi

 

What spring setting are you currently using?

Try turning the spring (top part) all the way to the softest setting (-). Then do two complete turns in the stiffer direction (+). Then try it. If you still notice any problems try doing another half turn or another full turn (+). You should also be able to vent 30% and recirculate 70% after this if you'd like some vent noise.

These are just the settings that other Evo owners have had success with with this particular BOV.