i have been reading that on maf cars it is better to vent the purge back into the intake. anyone got any clues why? doesn't seem to make a difference to me really if it vents atmosphereic or back to the intake, but want opinions on why i keep hearing this. thanks

 

because the maf has already metered that air. your blowoff vents to atmosphere and now you have fuel being injected without the air....rich condition results. It gets even more fun if you are running aux injectors... geee where is that fuel smell coming from?

 

well you would never try to purge it after the maf, i am talking about doing it before the maf. i have just been doing alot of research on bov lately and alot of them are suggesting purging back into the intake tract before the compressor on maf controlled cars. now purging before the maf atmoshpereically i think would not matter, but why are most companies recommending it purge back to the intake tract. perhaps the reason the greddy kit has no bov and just wastegates is for this reason. just trying to figure out if anyone knows the reason, lol.
my old ati kit had the purge set up to vent back into the intake before the compressor, but i installed a atmoshpereic bov and didn't really see any problems with it though.

 

i'm not one for turbo-savy tech info, but i believe the VW folks are into the same type of setups. they call it a "diverter valve" that essentially directs the blow-off pressure back into the intake. a friend of mine has one on his jetta and was trying to explain it to me; i was kind of actually wondering the same thing. good question

 

I am about to put a BOV on a TT setup, and I also have this question - should I vent to the atmoshere or back into the intake?

 

Not sure why it may be recommended to vent into the intake but see a problem with it.
Mixing boosted/pressurized air with atmospheric and dumping it into the compressor for additional compression is likely going to cause the blower to stall or operate at a lower than an efficient level.. Need a differential pressure across the compressor for it to operate efficiently..IMHO

 

a "recirculating diverter valve" is the optimal choice for any turbo charged vehicle. by putting the already metered air back into the intake (post-maf) you can improve turbo spool between shifts significantly. having a vta bov is a ricer mod! it does absolutely nothing better than a diverter valve, except make noise. every oem turbo car uses this provision.

oh and btw my aftermarket bov is recirculating

 

Yes you are correct in your post but you are missing the fact on all the turbo setups and SC's(excluding the not yet release JWT TT) all meter the air after it is pressurized. As long as the blow off valve is pre maf all is cool. In other words this is not a huge issue. It would help but on TT's it would be a PITA to recirculate the both intakes. It's not like on the EVO or WRX where a VTA blowoff valve with give you backfires because it meters the air and expects not nearly as much as it actually gets creating a rich condition and boom, backfires. Powertrip - I know you already know this. I was just doing it for everyone elses benefit.
Alan

 

My installer re-positioned the Vortech BOV and had it recirculate back into the intake.