Originally Posted by steve91t
Can the bypass valve be cracked open on the ground with the engine running?
Depends how you set it up. My return is pre-servo, not post servo. I drilled an orifice that would flow about 8-10 GPH through the return circuit with the return valve open. I designed it this way to insure that enough flow would be remaining from the fuel pump to support full power on the engine if I accidentally left it open, which I have done far too many times. The mech fuel pump will flow 35-45 GPH, so I have plenty of margin at full power. My injectors are in the primer ports and I will get stumbling when I go to idle on final and like to have to return open on landing to help reduce this when the ambients get hot.
My return starts at the FI servo, not the fuel pump to help take more heat out of the fuel. However, my situation is a bit unique and need to shed more heat due to the injector locations on the hot side of the baffles.