My car, like probably most of them, idles with a manifold pressure of -10psi (20inhg). Obviously the pressure on the other side of the throttle plate is something higher. I always assumed that the exact pressure depended on a number of factors (like the specific compressor, engine displacement, timing maybe?).

Well today I decided to check to see at what 'looseness' I could get my BOV to start leaking, and to my surprise I found that I couldn't make it happen at all. So then I decided to measure the pressure just in front of the throttle plate and found that is was exactly 0 psi. I'm trying to figure out if there is a reason why its 0 psi, or if its just coincidence for this particular 13t car.


(BTW, I made a rig to test my GReddy type RS and found that it holds an 11-15 psi pressure differential across its adjustment range. So a pressure differential across the throttle body of of just 10psi is not going to open the value at idle. Well, it probably opens it a bit, but not much.)