Those screws are actually very important. They control the flow rate from the boiler to the group. With proper tuning, you can figure out how long it takes to fill the group with x amount of water. For me, I'm at 18g in 36g out. I tuned all my groups (I have three) so that it takes 6 seconds under pre-infusion to dispense 36g of water. This way, when I return the lever to spring pressure, the group is only filled with about 36g of water. These valves are extremely sensitive, so tuning them is a little touchy. But once you have them set up, they make sure your ratios are on point without needing scales or having to pull the cups mid shot.

Thank you.

Boku Supper Club wrote:Those screws are actually very important. They control the flow rate from the boiler to the group. With proper tuning, you can figure out how long it takes to fill the group with x amount of water. For me, I'm at 18g in 36g out. I tuned all my groups (I have three) so that it takes 6 seconds under pre-infusion to dispense 36g of water. This way, when I return the lever to spring pressure, the group is only filled with about 36g of water. These valves are extremely sensitive, so tuning them is a little touchy. But once you have them set up, they make sure your ratios are on point without needing scales or having to pull the cups mid shot.

That is not how I use it at all.
I use it to make shots wirh a certain pressure profile. For me that is starting the lever at 11 o' clock.

Most of us have seen this video,
http://www.youtube.com/watch?v=liyNXTW41zA
I bring it up in view of the recent thoughts expressed and perhaps some clues.