There is an adjustment on the BOV that has arrows for "Harder" or "Softer". What does it do and how/why would one adjust it? (I know I'm setting myself up for some witty remarks, but please be gentle! )

 

I am assuming that you are referring to the Greddy Type RS BOV. The Greddy TT kit doesn't come with a BOV.

the adjustment is basically a preload adjustment for the springs inside the BOV. On my Type RS BOVs, I converted them to single spring (stock is dual spring.) My BoVs open up faster now, and I don't have any boost leak issues.

 

That's what I was wondering. When I hear the blow off, I also hear a loud turkey sound (gobble gobble). It doesn't sound right to me, but I was wondering if that adjustment was the key. Do you have a DIY on what you did?

 

I refer to that sound as a pigeon "cooing." that sound is the sound of air going backwards through the turbochargers. "reversion." you should set your BOV to its loosest setting.

the way I relieved the reversion was to go with 2 BOV.....one on each pipe before the intercooler......

 

So, by "loosest" setting, you mean turn the bolt in the direction of "softest" until it stops?

 

It's OK, I got it. I removed the smaller spring. No more turkeys. Here is how I did it...

 

that's the ticket! you have to be careful when putting it back together. It is very easy to twist the top piece instead of getting it staright down. if so, it'll torque the diaphram. if the diaphram gets torqued, it'll keep the BOV from closing all the way. You'll know because you'll be able to hear boost coming out of the BOV while accelerating.

when I went to single springs, I tightened the preload setting on the BOVs so that the valve wouldn't open up all the way. It prevented me from having any diaphram problems.

 

Thanks for the advice. I must have done it properly because everything is peachy now. Is there a problem with the valve opening all the way? (Isn't it supposed to?)

 

Nice pictorial

 

it is designed to open all the way, but with dual springs it won't open up that far. there isn't that much pressure and vacuum to do it in most setups. If there is, it'll only be a for a split second.

when you go to a single spring, the vacuum at idle is enough to open the valve all the way.

 

if your still wondering what the gobble gobble sound it, its your wastegate fluctuating.. its normal

 

Ah... well, I did the "single spring" mod (shown above) and the turkey sound has been replaced with a very gentle pigeon if anything at all. The blow-off is now clear and unmistakable. I'm thinking the pigeon could be the wastegate, but the turkey was definitely bad news.

 

the sound you are hearing has nothing to do with the wastegates.

what you are hearing is reversion of the air coming back out through your air filters.

the greatest area of pressure buildup is between the turbos and the intercooler. if you put BOVs on each pipe going to the intercooler, you eliminate all reversion.

I have a Greddy TT kit, but I went with the SFR intercoolers to better work with my sedan bumper. I had a greddy RS BOV welded to the endtank of each intercooler. additionally, I am running only single springs in each BOV. I have no reversion at ALL!!!

 

Wow! Are those braided vacuum lines? Where did you get those?

My reversion is extremely minimal now. My BOV is way up on the "out" end of the Greddy IC. I could probably put another BOV between the "in" pipes on the other side if I want to eliminate it completely. I can't see putting another 2 on one on each "in" pipe.

 

they are all -4An lines on all my vacuum lines for the BOVs and the Wastegates. the Greddy BOVs had to be retapped to 1/8NPT. Greddy uses some other sort of pipe thread that is very close to 1/8" NPT. I just ran my tap in there, and it worked great.