Well, I'm almost a month into learning to use my ECM Synchronika. While I ordered it with the Flow Control Device (FCD), it was shipped in the standard configuration, and the FCD was later shipped separately. I spent most of this time, learning the basics of the machine in stock form. I've had a range of success, and attribute most of the failures from trying too many things before mastering anything. Different size baskets, different brand baskets (ECM/VST), with/without puck screen (BPLUS), puck building variations, and different coffee/roast combos every three of four days. I've at least found a few consistencies for what works well and what doesn't.
I moved forward and installed the FCD last weekend, and have been playing around with it this past week. Have had mixed results there as well.

My Preinfusion Background
For the last couple years, I was using my old spring operated lever machine. Controlling the preinfusion on this machine consisted of manually opening the water chamber of the group head and holding the lever in this position, while the water in the chamber was applied to the puck, under pressure from the boiler. My best results for the roasts I typically did, was to start this as the boiler temp/pressure was on the rise, starting from .7 bar. As the boiler pressure continued to rise, that pressure was applied also through the group head onto the puck. The boiler pressure was set to stop climbing at 1.25 bar. I was typically achieving good results, when I would see the bottom of the basket fully/evenly developing droplets forming within 10-20 seconds, depending on roast and grind. At that point I start the pull.
In this process, as long as I built the puck properly, I would typically be able to gauge the grind and dose adequacy while dialing in. If it started gushing during preinfusion, or it took way long for the droplets to appear, I knew which way to adjust, to get in the ballpark when dialing in. My starting point was always consistent though, i.e., the beginning wtr pressure, and max wtr pressure through the preinfusion step.

Now, with the Synchro, I'm faced with a significantly different set of parameters to work within. Figuring out a consistent pressure, and how to consistently achieve it within this preinfusion stage is not as simple as it had been with the lever. So, here's a few questions I hope make since as to why I'm asking:

I would like to hear from anyone who uses a bottomless portafilter, and conducts preinfusion with the Flow Control Device during dial-in.

Q1. I wish to know what if any, benchmarks you go off of, during the preinfusion stage, to judge if you have your initial grind and puck prep in the ballpark, for the particular coffee you are preparing.
Q2. I would also like to know how you proceed with the FCD adjustments for this pre-infusion, timing, pressures at brew head you are looking for through the preinfusion stage, and any specific pump lever manipulation along the way.
Q3. Finally, what technique do you follow to transition from the end of preinfusion to full pull pressure, say at 9 bar?

For me so far, I'm finding that the grouphead pressure gauge is a bit slow in reading the initial pressure build up, then it seems to take off.
I find that I should just crack it open after turning on the pump, if I don't want it to take off, then be patient and wait 10 seconds or so for it to start registering an increase, and climb slow enough that I can stop it soon enough. From that point, I'm, still trying to figure out how much pressure makes since to allow it to go up to, and what's the best way to stop the pressure rise during preinfusion.
My findings so far have been that a grind/dose level that pulls well without preinfusion, seems to get too wet too fast during preinfusion. Conversely, a grind level that starts forming droplets after 10-20 seconds, typically pulls waaaay too slow. From a benchmark standpoint for dialing in, I'm perplexed by what my preinfusion control points should be with what my dial-in grind level should be. I've read here in places, that the preinfusion should be 2-4 bar, but that's far higher than I ever needed on my lever machine.

Perhaps I should add that I generally have been dosing towards the smaller side. 15 grams on average with the Synchro. I was used to dosing 12-13 grams on the lever, and haven't found the need to go up to 18+ grams with this new machine.

I recently shared my current flow profile routine in another thread posts #2 and #6. Additionally Jim chimed in at post #12 to offer a very similar suggestion only explained in terms or pressure steps instead of flow steps:

Most useful visual input for effective flow control?

Hope this helps.

I did see this discussion, thx for referring it to me though.
After taking the time to form my questions above, I slept on it all, and awoke with some of the fog lifted. Dr heal thyself. I have found the following to work consistently well for me since then:

1. I am basically following the same benchmarks that gave me success with my spring-lever machine, but adjusted to compensate for the pump and flow controls.
2. I start with FCD fully closed and bring pump on-line. Timer starts automatically when pump is activated.
3. I just crack open the FCD, and glance down at the bottom of the basket, watching for signs of channeling while I wait a bit for the grouphead pressure gauge to start registering a pressure increase.
4. I allow the grouphead gauge to climb pressure up to about .7 bar, where I close the FCD, and check the basket. If things are correct in the basket, I should see liquid beads starting to form.
5. If still no channeling, I crack open the FCD a bit and allow the pressure to rise up to 1.25 bar, and close it. Now I'm watching and waiting for the basket to fully become involved with the beading liquid, and for the first drops to form. I still need to settle on a normal time through this stage for benchmark purposes. So far it's looking to be about 10-15 seconds, which reflect what I saw with my lever machine at this point.
6. Upon the fall of several drops into the cup, I now initiate full pressure with the FCD, opening it up rather promptly to allow the pressure to increase up to 9 bar.
7. As long as no channeling has erupted, I now watch the pull for both color change and volume released. As it starts to look about 2/3's through the extraction (judgement call by appearance and volume), I begin to steadily/slowly reduce the flow, trying to finish at the end of the desired volume with reaching back down to 0 bar, shut off of the FCD.
8. Then I fully lower the main lever, shutting off the pump, draining the grouphead, and stopping the timer stops.

This procedure has consistently delivered the best shots to date on the machine for me, and has been reproducible several days in a row. I'm still working through the coordination of all of this, developing my reflexes so to speak, and have not really used the timer to govern anything, other than a reference. My shot this AM, which was near prefect in terms of no mess, correct ratio, and great taste went 80 seconds from the time I first powered on the pump and the timer auto-started, until I finished the pull, then shut the pump back off and the timer auto-stopped. Unfortunately, I'm down to just 1-2 more doses of the current small batch roast I have been using through this series. However, I'm confident that I'll now be able to follow the same basic processes as I used on my lever machine, to incorporate the preinfusion stage's behavior while dialing in.

For reasons outlined in the other thread a fast fill will provide a more even extraction vs. a Slayer style shot as you describe. The idea is to get the whole puck wet as quickly as possible and then hold/Bloom it under 2-3 bars of pressure until you completely saturate it and it has had a chance to swell and heal any potential channels. Give it a try.

I'm unclear on how best to accomplish the "fast fill", in a controlled fashion. Are you opening the FCD @ 1/4 turn and and waiting for a surge of pressure to take off on the grouphead gauge, and hope to shut off the FCD at the right instant some point under 2-3 bar?

As per my posts in the other thread here is my current routine:

-set FC to a position that gives ~7.5ml/sec and run for the first 4 seconds
-move FC to the 4ml/sec position until the pressure builds to 2-3bar
-close the FC and wait until ~20 seconds from the beginning of the shot
-you should have ~2g in your cup by this point if you've dialed in you grind correctly
-open the FC back up to the 7.5ml/sec position for the main extraction
- you can taper back the flow but most of the time I don't bother

I'll quote myself here by way of explaining the fast fill stage as well as the rest:

Pressure is an outcome (or result) of flow. Think of it this way, you've created a high integrity puck of finely ground coffee and locked the portafilter in place. In doing so you've built a (temporarily) finite amount of space. As you start the pump and force water into that space initially the pressure does not rise as the water first fills the headspace above the puck and then is absorbed by the coffee itself (which can hold about 2-2.5 times its dry weight).

Once the coffee begins to reach saturation, that's when pressure starts to build. One of the things we learned from the Decent Espresso machines is that a puck can absorb water at a maximum of about 3-4ml/sec. In a perfect world you want all of the coffee to get wet (which begins extraction) as quickly as possible. The amount of pressure applied (I'm aiming for 2-3 bars) at this pre-infusion stage speeds up getting the bottom of the puck saturated so it reaches a state of equilibrium with the top of the puck in the shortest amount of time possible, thus avoiding a top to bottom unven extraction gradient.

So, I put a bunch of water (7.5 x 4 =30g) into the system right away and then move to a lower 4ml/sec flow so I have better control over hitting that 2-3 bar target for pre-infusion pressure to force a quick saturation of the puck. I do this usually for ~2-4 seconds which adds an additional ~8-16g of water, which means I now have enough water in the system to fully saturate the ~18g puck.

My next goal is to keep the pressure below 4 bars until I get to ~20 seconds on the shot clock. Usually I don't have to do anything once I close the flow control as the pressure hold is already setup in the previous steps. This allows for full wetting and reorganization of the puck before it compresses and no longer can swell and fill in gaps in the bed. When you have the grind dialed in this should give you about 1-2 g in your cup just as you hit that 20 second point. Then you can open the flow back up and let it hit your peak pressure. Mine is usually 8-8.5 bars.

A video of this workflow shown beginning to end, and including a real time view of the basket discharge would be cool.

Good comments here. I'd just add that there's no need to close the FCD control totally to stop the flow. On an e61 (with good seals ), just drop the brewing lever to the mid-position for the soaking phase.

Rustic39 wrote:A video of this workflow shown beginning to end, and including a real time view of the basket discharge would be cool.

I agree. It's on my list of things to do when I have time. It's really much simpler in practice.

Nunas wrote:Good comments here. I'd just add that there's no need to close the FCD control totally to stop the flow. On an e61 (with good seals ), just drop the brewing lever to the mid-position for the soaking phase.

I don't agree with this. When you raise the lever to the middle position and when you reengage it you risk unseating the puck from the sides of the basket if the pressure shifts. With the pump running you keep a steady 2-3 bar of pressure in the system.

FWIW I have my flow control set so it bottoms out on the nut JUST before it really hits fully closed to reduce wear on the needle valve itself but in practice it's only a drop or two every second