[Freemorfeem]

Originally Posted by iqraceworks

Just keep in mind, if you get a bov spring that's too light, sometimes you can have bov fluttering that causes issues. That's what I had on my bov when I was running just a slightly too light of a spring where was open at idle.

It did this weird fluttering thing at part throttle. Didn't really cause any issues with the motor running, it just felt and sounded weird. Putting just a slightly stiffer spring in there where it's just slightly closed at idle got rid of all those fluttering issues.

Ok, I also sometimes get the same BOV flutter at part throttle—sometimes (& is it that or a boost leak?!). That’s what caused me to look into this initially. I didn’t notice it until I did a COWL delete and could hear all the air noises. I have afe DC intakes that hiss, too. So being a noob it’s been tricky to know what the air sounds are. But when I think my BOV is blowing off on partial throttle I also feel I’m losing power. Now I might be wrong here in that it’s not the BOV but is a boost leak somewhere else.

My first attempt at a DIY smoke test didn’t go well. Hahah. But I just got a transfer pump and I keep a humidor of cigars so I’ll be rigging this one up soon. If I find a boost leak my attention will go there. If I don’t I might try getting the Synapse BOV to be just barely closed on idle (if it’s adjustable). I do recognize from this thread and watching SYNAPSE BOV videos and reading their manual that the default with Synapse BOVs is to have it slightly open on idle.

[C.Pop]

Originally Posted by iqraceworks

Just keep in mind, if you get a bov spring that's too light, sometimes you can have bov fluttering that causes issues. That's what I had on my bov when I was running just a slightly too light of a spring where was open at idle.

It did this weird fluttering thing at part throttle. Didn't really cause any issues with the motor running, it just felt and sounded weird. Putting just a slightly stiffer spring in there where it's just slightly closed at idle got rid of all those fluttering issues.

That's a good point. Really depends on the tune and the strategy used by the tuner. I have seen more lazy tuners lately letting throttle closure do a lot of the work of smoothing things out -in that scenario, you'll want a stiffer spring to avoid fluttering, but then you're going to have the tradeoffs with doing that.

A better solution is a proper tune that doesn't ride DME safety controls, smooth power without surging turbos or unnecessary throttle closures. I recognize that isn't available to everyone, so YMMV. From the isolated perspective of the BOV, you want it open, but yes, there are situations that the easiest path forward is to put a little stiffer spring in there. Watch out on upgraded turbos, really easy to surge them down low in part throttle situations.

[Freemorfeem]

My synapse BOV is actually wide open at throttle. I was saying “slightly” but looked again. It’s totally open on idle.

[Freemorfeem]

There is not a one-size-fits-all answer here, hence the confusion and varying answers, which even though they contradict might all be "right" for that person's set up.

I read up on how BOV's work, as was suggested here. I can attach the image showing and saying that the BOV should CLOSED at idle.

I also looked into Synapse BOV's FAQ which emphatically reassures, and recommends, that the BOV be OPEN at idle.

I think seeing mine wide open recently and not "slightly" open was the difference between a cold engine and a very hot engine. It is a bit more closed when hotter.

I am going to experiment with the PORT configurations, now and after I tune this beast.

Thank you to everyone. This has been very instructive!

[Freemorfeem]

Quick update for anyone following this.

I’ve left the BOV in the default state that Synapse recommends. Open at idle.

I found a boost leak on both hoses going into my new oil catch can. Just added hose clamps and solved it.

For the smoke test I used a $10 transfer pump from Harbor Frieght, 2” pvc pipe caps, and two grape flavored swisher sweets

The test drive delivered! Very smooth acceleration curves compared to before. More predictable and consistent through the gears. And the Psshh is a bit louder.

She’s ready for a Tune!

[jp77]

Originally Posted by Albertn54

My blow off valve stays almost completely open at idle but it seems to function when I drive
Is this a problem or am I good?
I have an automatic 08 335i

@Albertn54 I also have a 2008 auto 335i, installed my BOV today. Mine stays open during idle. It seems to be working fine so far. My bov came with a firm spring and a weaker spring, I'm currently running the weaker spring. I hope this helps!