I know that since my S5 TII has an AFM that means I have to recirculate my blowoff vale, or so I am told.
My question is what do I need and what do I need to do to be able to run a regular blow off from Greddy or HKS or something? Also can I just let my stock BOV dump into the atmosphere or will that cause problems? I am curious because it seems that the stock BOV dumps the discharge air back in right AFTER the AFM and not before it. So, why would it matter if it is plumbed back in or not?

 

lol. We just had a topic on BOV's and I was correct on this exsact matter.
Yes you can dump.
The air is allready meterd from the MAF, so dumping befor the MAF is remetering it. This will double meter the air runing 2 times as rich as if you dumoped. If you dump the ECU is adding fule for what it dumped. It is not a big deal but not 100% perfect.

To recirculate you need a BOV designed for it. If you have one the horn will screw off and you can screw a fiting onto it from any hardware store and plum piping back into the intake. Or you can buy a fiting form the BOV company some times. I am thinking about using the hole in the TID from the BACV since that is removed on mine.

 

If I remember correctly, the AFM has already measured and accounted for the air that is being discharged by the BOV. That is why it must be recirculated into the system instead of being dumped overboard.

If you had a setup that measured absolute manifold pressure that was taking its reading somewhere after the throttle plates, then your BOV could dump air overboard because the air hasn't reached the manifold where it would be accounted for and have fuel scheduled for it. If I'm completely wrong then I'm sure someone will jump at the opportunity to say so.

 

I need to leave a word befor people freak out on my above post lol. If you recirculate befor the AFM 2 things can happen. It just dumps into atmospher realy. Or if you point it towrds the AFM as I was refering to in my above post it will remeter the air actualy with a burst flinging the flapper open.