Ok I’m trying to sort out a few things prior to my car going onto the dyno very soon. One of which is trying to understand the operation of the dump valve.
Please correct me or tell me why it operates in the way does.
I totally understand that when you lift off the throttle the pressure in the inlet tract is released thereby preventing the turbine from stalling and adding shock loading back onto the shaft.
What I don’t understand is why the dump valve is open when the inlet tract is under negative pressure and it only closes when there is a positive pressure in the system?
Especially from a supercharger perspective where boost is being added continually as the revs rise, surely it is better to maintain this pressure until the throttle is released?
Under the very limited testing I can do at present due to keeping the revs sensible when I set the dump valve to open at idle the engine makes 2.5psi less at my imposed rev limit than it does when I set the valve to be closed at idle!
Maybe these type of dump valves are good for turbo installs rather than supercharged but even the supplier of the sc suggested using a Forge Motorsports supersize dump valve, and as far as I can ascertain that also works in the sameway?
Please enlighten me.