Another Barrel Valve question

If you have a flow meter I much prefer to use gpm at idle than leak down percentage, which is not as accurate. There can be a big difference in 72% on my leak down tester and yours.

 

Let me add a few things here. The correct leak down percentage depends on the set poppet spring pressure of the idle return poppet. In other words if you have 8-9 lbs crack pressure your leak down will be in the 82-84% region but if you have a 20 lb crack pressure then your leak down is going to be in the 76-78% region. The correct way to set the idle of your barrel valve is to set the idle return poppet spring pressure where you want it use a leak down tester to put it in the 80 % region and start up the motor and warm it up and then check the off idle response of the motor by quickly operating the butterfly linkage. If it blubbers it is too rich and if it hesitates then it is too lean. You want a crisp fast off idle response and adjust the linkage to get that. Once obtained then hook up your leak down tester and find out what percent it is and record it so you can always go back and set it again plus you can look at the flow meter data once set for a reference. You can't just pick a percent and say that is what you want you need to adjust it for response.

 

To stop surging at idle especially when using a big pump on a screw blown moter