Two BOV's or one?
07-07-2006, 09:53 AM
#2
Drifting
hhhmmm, that's a new one to me for a single turbo application. I can offer that one of the most critical things to consider if you're looking at tampering with the OEM BOV (replacing it with the long neck type used on the 964 Turbo), is that you must not vent to atmosphere...IF YOU INTEND TO KEEP CIS. I'm told that this causes fluctuations with the fuel/air metering plate and can cause a lean condition if it dumps shut. In other words if you keep CIS, keep the BOV as a recirculating type valve. There are some threads floating around about this.
07-07-2006, 12:39 PM
#3
Three Wheelin'
I have also heard from reputable tuners/builders that a BOV should not be used with CIS for the same reasons. As for needing one or 2 (assuming EFI is in the equation), there really isn't any reason you'd need more than 1. Some Japanese sports cars have aftermarket twin BOV setups (Supra, Skyline, etc), but this is really just for the "bling" factor. There are plenty of BOV's like the HKS super sequential, HKS racing type 2, etc that can handle anywhere from 36-50psi, so there is no reason you'd ever need 2. Heck, if someone was running over 50psi on their 911, I will personally buy them a BOV! 
