Atmospheric or Closed Loop

[poppincaps88]

Why use an atmospheric BOV when a closed loop yields better performance?
What do you guys prefer?
Seems kinda stupid to lose all that boost pressure on every shift....:nono:

 

[robbo185]

if you shift fast you dont lose all the pressure. Search this topic has been covered millions of times...youll find the answer

 

[Troyota]

I think it has a little more to do w/ the fact that all that air that has been accounted for by the MAF is now being released from the systems messing up the A/F ratios. I could be wrong.

 

[jetjock]

Well, you need to "lose" it. When you come of the pedal during a shift the throttle plates close while the intake manifold is pressurized. This creates a shock wave in the intake tract that is hard on the turbo's compressor vanes. Plus it kills some of it's speed. Dumping the boost equalizes the pressure, thus minimizing the shockwave. So you need to do it for the turbo's sake and to keep it spooled. Whether to dump to ATM or use a CBV is up to you but, as Troyota correctly points out, you also need to consider when dumping to ATM that the air has already been measured by the AFM.

 

[poppincaps88]

well heres my thinking, i'm sure if you're running 20+ psi the pressure needs to be released, but what about all these setups that are only running 10 - 15 psi.

I read an article a while back (maybe I can find it) it was discussing closed loops versus atmospheric. They took a modified car to the track and tryed both types of BOVs. The closed loop seemed to reduced the time by 2 seconds. Admitidly driver error could also be at fault but it was a pretty substantial difference.

Rally cars used a type of recirculation BOV don't they?

 

[robbo185]

use both...its been done

 

[isnms]

i have both. i was getting compressor surge with just the bosch so i added the Blitz.

 

[poppincaps88]

i have both. i was getting compressor surge with just the bosch so i added the Blitz.

I guess you answered my question for me then, I was just about to ask why use two. So with closed loop is compressor surge always something you have to worry about? It's not making sense to me...why would they make a recirculation BOV if there is always the fear of compressor surge?

 

[isnms]

closed loop, like they've already said, keeps air in that has already been accounted for by the afm

 

[GrimJack]

Ok, some people are still obviously confused.

Compressor surge only happens when the BOV isn't large enough, doesn't work properly, or doesn't exist. It has nothing to do with whether it's plumbed to atmosphere or back into the intake.

A 2 second difference between recirculated and atmospheric BOV is ridiculous, and must be driver error or something else. It will not make that much of a difference unless something is seriously setup wrong.

Atmospheric BOVs sound cool, but are often setup wrong in that they lose metered air. This is not a requirment, however, you can switch to a different air metering system with a MAFT, for instance, move your air meter to after your turbo (blow through mode) and mount the BOV before the air metering device.

Recirculated setups can theoretically respool the turbo faster, as there is less drag on the compressor wheel. In practice, you would have to build some sort of measuring device accurate to miliseconds at the least to verify this. Car manufacturers like recirculation setups because it's easier to make sure you aren't venting any contaminated air... and places like California are hell on emission laws.

Hope that explains everything.