fasteddie313

I'm wondering how your BOVs operate.. I feel like mine is opening way too easily basically just from the manifold vacuum to its reference port.. Like almost any sort of decel is opening my BOV and even manifold vacuum at idle has the thing on the brink of opening all the time..

I even put 2 washers in it to shim the spring tighter, have the thing tightened up all the way for the most spring pressure, and I still feel like it opens way too easily..

My problem is that my BOV is after my MAF, a draw through MAF, and the BOV is changing my tune..

I have been running my BOV recirculating so in order it goes , MAF - BOV plumb back line - compressor - BOV - TB , so the BOV can't get any air in that the MAF didn't see nor let any air out that the MAF did see, but I have been trying to get it to run with the BOV open to atmosphere because it makes a much better sound, but it is screwing up my tune.. It tunes fine plumbed to recirculate because the MAF sees all, other than it causes a lean spike when it blows off but I don't care much about that because I'll prolly be running fuel cut overrun anyway..

Is my BOV just junk or is this how they work?

I think I could just retune my car to compensate for the BOV but that just doesn't seem right..

Like high vac cruising down a hill or decelerating in gear the darn BOV is letting in unmetered air if I have it open to atmo..

I think this is the one I have..
https://www.ebay.com/itm/25mm-Bov-Al...YAAOSwbqpTtWs1

It seems pretty nice and well made, it even has an O-ring for the cap and another around the piston, but doesn't work for crap in my case..
Maybe I should just try to find heavier springs for it?

shortyboy

If you're trying to vent to atmosphere with a draw through maf setup it will run rich during shifts and stumble. That's because your a venting metered air, where it supposed to be in the engine combusting with the fuel the maf calculated. So no air ( since you vent it to atmosphere) and more fuel, means your car will run very rich. Either plumb the bov back to the maf, convert your maf to blow-through maf or run a standalone engine management to use a vent to atmosphere bov.

fasteddie313

Right but the blow off isn't the problem for me, I think I have that handled..
The problem is that the BOV is letting unmetered air come IN when I have high manifold vacuum on the BOV signal line and slight vacuum between my MAF and TB pulling air IN my BOV..

shortyboy

Could be possible you have it reversed. For piston type bov, the bottom of the piston faces the intercooler pipe. It's either that or you have a leak in your bov ( oring seal or weak spring like you suspect) or leak in intercooler hoses letting the air in also.

fasteddie313

It is not reversed and I am absolutely sure it is the BOV because I can very easily do back to back testing by putting the plumb back recirculation line back onto it and logging both ways..
I think I'll try springing it to the moon and see what that does..

fasteddie313

BOV open to atmo on decel.. It goes stupid lean..



BOV recirculating on decel..



The tune still needs some work and this log is a bit rich in overrun but I have pulled more VE out of it there since then.. Tune in progress..
But you can totally see the difference with the open BOV letting in a ton of air on overrun in the first log....



Here is a pretty sexy looking log though of what I have been working on the most.. This is not decel..

JustinL

Is your throttle plate not closing? Usually even at idle the turbo is spinning enough to move air into the intercooler piping and you get an outflow from the BOV if the spring isn't strong enough to keep it closed. I can't really see the piping in that picture, but where does that T go that is right before the BOV?

fasteddie313

Back side of the brake booster venturi thing that connects back to the intake side, and a TB bypass with a ball valve to set my idle..
Their is no active idle adjustment..

JustinL

I'd try replumbing that. As a test, just unplug the idle valve and let it pull from the atmosphere and see if the flow reverses through the BOV. I suspect that teeing into your BOV line is turning that line into suction instead of pressure.

fasteddie313

Ok, I can completely close both of those and try some tests with no idle and stiff brakes..
You might really be onto something with this idea that I have so far overlooked, because all my TB bypass air is coming right from there on that T..
The TB just closes up tight, has no idle adjustment on it..