Great video.

Interesting that on my synchronika if I build up to 2 bar and shut off my pressure does go down, but once I open up to the full rate and then lessen the flow I still stay around 9 bar which my machine is set at. The pressure really doesn't change. I've used the matrix and ims 35 screens. Maybe I'll try a different screen or is my fcd not working right? Flows are adjustable like the name or I shouldn't worry about pressure.

Pressure, as it is what you can measure reasonably and without a lot of delay, is worth paying attention to during the phases after the basket fills. There are also some reasonable arguments as to why lower pressures than the classic 9±1 bar can have lower shot-to-shot variance and potentially better flavor.

To reduce the pressure more than a tad from pump bypass / OPV pressure, the control valve needs to have a significant restriction compared to the restriction that the basket/puck is presenting. This means closing it down, perhaps quite a bit from where you're running it today. How much will depend on a lot of things including machine, coffee, grinder, grind, dose, preceding steps, and hopefully not too much on uneveness in prep within the basket or shot-to-shot.


(The names in mL/s people give to various angles of the handle won't have much to do with the actual flow rate when the basket is full.)

Jeff wrote:(The names in mL/s people give to various angles of the handle won't have much to do with the actual flow rate when the basket is full.)

Yes, the actual flow during extraction at different positions of the FCD valve stem will depend on lots of variables. You can see that's the case from the fact that no where near the stated flow rates were passing into the cup in the video...I assumed, logically enough, that the OP was referring to the measured "free flow" from the group without a portafilter inserted.

bonjing wrote:Great video.

but once I open up to the full rate and then lessen the flow I still stay around 9 bar which my machine is set at.

This is a key distinction here and the root cause of this misunderstanding is not fully understanding that flow will result in pressure which will then in turn result in less flow.

You have to move your flow control to the zero flow position at a very specific point in the pressure ramp or else it will get away from you and you won't be able to decrease it with any precision.

Remember, we are discussing machines with control over the flow variable. We don't have direct control over pressure with these devices. But we CAN manipulate pressure with flow. It's one of those things that once you get it, you get it but until you do it can be very confusing.

Pressino wrote:I'll have to make adjustments for the max pressure difference between the two pump types.

I assumed, logically enough, that the OP was referring to the measured "free flow" from the group without a portafilter inserted.

Yes, I am referring to the measured water debit at a given position which is the amount of water that will be delivered until pressure begins to build. After that point the input flow rate will be forced to slow down due to the system being full. The opposite happens at the end of a shot when the puck has eroded enough to allow the pressure to begin to drop and therefore the flow will increase unless you control it by slowing down the input.

The reason I state in the video the positions of the flow control in ml/sec is so anyone can calibrate to the physical position of the knob on their machine which may very well be in a different physical position to mine. You are correct that rotary pumps will have a higher maximum flow rate than vibratory pumps.

So I tried your method but still can't moderate the spike in pressure after the first 4 sec. The pressure goes all the way to 9 bars regardless the drop from 7.5ml/s to 4ml/s. If I close it fully then it will drop to 2 bars and then to complete zero. As soon as I open the valve very very little, the pressure builds immediately regardless the level of saturation/erosion of the puck. My FC is set to fully close the flow.
Will keep on trying, that is for sure!:) Next thing is to go a bit finer with the grind.

The timing is very important and I'd say the exact number of seconds is less important than nailing the exact point in the pressure ramp. Watch the video for how the interaction occurs.

One thing that came to mind is that I have the original bottom spring in my group which is what provides that SLIGHT pause/pre-infusion in a standard e61 group. If you've replaced the original spring with the one that comes with the flow control kit you may not have that extra second or so of timing get to the zero flow position. A way to find out is to set the flow control to the normal 7.5ml/sec position and pull a shot without using it. If you see a little pause in the pressure gauge around the point where it hits ~3bar you have the original spring. If you don't see any slowing down then you have the newer flow control spring that removes the tradition e61 pressure ramp. Maybe try putting the original back in.

If you can time it so you catch the pressure at 3bar and then shut it to the zero flow position the pressure will begin to drop. If it stabilizes at 2bar then I know I've nailed the grind setting. If it continues to drop in pressure before I get to the end of my pre-infusion (20 seconds) then I know I'm a hair coarse in the grind. I can compensate for this by opening the flow a crack while I watch the pressure climb back to 2bar. I'll adjust the grind on the next shot and then things are usually spot on.

Hope this helps.

Interestingly my pressure now lowers when I reduce the flow

Sounds like you might be getting the grind and timing of the steps dialed in. Keep at it. I can assure you it's an almost mindless routine for me now and absolutely repeatable shot to shot. This morning I pulled 4 shots of Hatch Supernova that all ran 38-39 seconds total with between 33.0-33.3g in the cup.

I think that must be it - the spring. I have the FC Profitec version (stiffer). I tried many many times to replicate your technique and I can't keep the pressure still no matter what - grind size, dosing, tamping, adding filter paper, etc.
I am fast enough now with my technique to feel the build-up and close the flow when the pressure rises around 6 bars but if I keep it closed then the pressure will decrease to zero and rather quick. I have to give it some slight kicks from the knob ( literally 1 mm opened) to raise the pressure again. And it is not steady so I quit.
What I do know is to start at 1 full turn, let the puck soak and as soon as I measure the first 3-4 grams in the cup, ramp it up to 1,5 turns (7-8 ml/s) and decrease from there towards the end of the extraction.
I have been reading the opinions on the stock E61 spring but still puzzled whether to go back to it or not. Will it be such an improvement? I already enjoy less water waste with the stiffer one, I remember I noticed the difference immediately.
Thanks for sharing your thoughts and findings!

You can easily find a "standard" E61 pre-infusion spring to replace the stiffer springs provided with the E61 FCDs. If you want to use "traditional" E61 pre-infusion technique you have to replace the stiffer spring. Folks (myself included) have tried to emulate traditional pre-infusion by fiddling with the FCD valve. It may be possible to do so, but it won't be easy.

With the softer spring in place not only can you do traditional pre-infusion, but you can do it with added control provided by the FCD and you can still use all of the other customizable brewing abilities provided by the FCD.