As you already know and read i guess, the FCD job is to let you manually control the flow of water entering the coffee puck during extraction.
Instead of the pump always pushing water at full flow, the FCD lets you slow down or speed up the water delivery by turning the knob left or right.
How to Use It properly?
Turn knob clockwise → restricts water flow (allows slower pre-infusion, gentler pressure build-up)
Turn knob counter-clockwise → increases water flow (faster pressure build-up, more traditional espresso style) and take into consideration that in most cases, a full 2 and a quarter turn can give you almost double the standard flow rate your machine had !
Gentle Pre-Infusion Profile – most used on the market
Start with the valve almost closed.
Let water gently soak the puck for 10–15 seconds.
Then gradually open the valve to full flow.
Most common result: smoother extraction, reduced channeling, sweeter flavors. Great for light roasts.
Declining Pressure / Flow Profile
Begin extraction at full flow to saturate the puck quickly.
After 10–15 seconds, slowly close the valve to restrict flow.
Most common result: softer finish, more clarity, balanced body. Often used for medium roasts.
Flat / Constant Profile
Keep the knob in one position the whole shot.
Adjust to a medium flow for a consistent extraction.
Most common result: stable, repeatable shots, good for everyday use.
Experimental / Slow Drip Profile
Keep the valve limited the entire shot.
Produces something closer to a “lever-style” extraction.
Most probable result: intense, syrupy espresso with heavy body.
Make small adjustments — even 1/8 of a turn changes the flow noticeably. Take into consideration that you will always have a small delay AFTER knob adjustment, between what you just did and what you will see on the group head pressure gauge !
Watch your brew pressure gauge and shot time for feedback.
Pair different profiles with different coffees: light roasts usually benefit from longer pre-infusion, while darker roasts often prefer a faster start.
Keep track of your settings to repeat successful shots.
