Quote:
Originally Posted by RPM90
Just for clarity sake, because things get promoted in these forums as if gospel.
I'm sure you guys are hearing what you say you hear.
However, you are not hearing a "BOV". I know some of you know this, but it seems some don't get this.
A real BOV is night and day difference in sound and volume compared to a recirc DV.
With a DV the pressurized air is not being "blown off", it is recirculated, or returned, into the intake path. A "blow off" does indeed blow off/out the pressurized air to atmosphere. That's why it's so much louder, and cooler. 
Given that the N55 has not throttle plate, as it uses valvetronic intake control, it really is a unique system. With a standard throttle plate, once the plate is closed, the pressurized air leaves the BOV or DV, so that there is no more pressurized air going to the intake manifold. But, with valvetronic, the air intake to the combustion chamber is controlled by the action of the intake valves. So, imagine them as individual "throttle plates". This probably also adds to why the N55 can should hold boost better in between shifts, even with a manual trans.
I need to look into how this N55 engine works, more closely.
I'd also think that the DV is located in a different area compared to the N54. The location of the N55's DV could also lend to hearing it better/louder. |
I'm not sure anyone is claiming they hear a "BOV".
However, based on what I hear in my car every day, and the input from others here, the operation of the DV on the N55 is significantly more intrusive than the N54. If I accelerate hard out of a signal light (like if I need to get over a couple of lanes), I can hear it inside the cabin when the radio is off. With the windows down, it's a clearly audible 'pksssssss' sound. Very different than the chatter of some BOV designs, but definitely the sound of air being pushed hard through an orifice.
Sometimes I like it, sometimes I wish it didn't happen. I recently picked a colleague up from the airport in Tampa and he heard it go off as I accelerated on an on-ramp. His immediate impression was that something just "blew out". I told him it was just the DV and he looked at me like I had three heads.