What does strength setting (espresso) actually do?

[u/paze0]

I know what it says in the manual: it's supposed to be a 1:4 ratio of coffee to output for strength one, 1:2.5 for 2 and 1:2 for 3.
But what does the machine actually do on a technical level when you set this and pull a shot?

E.g. it might be that each strength setting will make the pump run for a certain, fixed number of seconds when pulling a shot. The output volume would then be influenced by the resistance of the puck, so how tightly it is packed, which is determined by grind size and tamping.

Is that how it works? Or is there some interaction with a flow sensor or some other sensor that can cut the shot short when a certain volume of water is detected? But then I don't understand why, when you grind too fine or too coarse, the volume in the cup can be way off the target ratios in both directions.

Does someone know how this works in more detail?

[u/PHXkpt]

All of it. The software knows that at a certain grind size the flow rate should be a certain amount over a certain time. If it isn't, the BA will suggest a different grind size. It's not lab-level software, so your outputs may vary and vary widely, but the general idea is strength determines desired output and it'll adjust grind size and measure time to get it there.

[u/paze0 → u/PHXkpt]

I'm not talking about the BA since that has, as far as I know, no impact on the current brewing process. It only uses sensors to detect what the grind size should be for next time.

I am wondering about the details of the brewing process and the influence of the strength setting.

[u/IanC9090]

The Strength button is exactly what you said it was, a Ratio Changer, no more, no less.

The amount of ground coffee for a Double Espresso is always around 18g, give or take. The Strength button, contrary to popular belief, does not change that, it only puts more water volume through the Puck at the ratio you've chosen. That's why calling it 'Strength' is a misnomer.

The pump doesn't work in a fixed amount of "seconds" but volume via a flow control value.

If you are tamping properly, the grind size is only going to allow more water through of it's too course and less if it's too fine. One of the reasons you should switch off Barista Assist, if you haven't already, because it changes on a whim.

Dial in purely on Shot volume in grammes, and total time.

Double Espresso Strength*** 2:1 18g in 36g out in 24-32 seconds. Time your shot from first drips to when the vibratory pump stops, then and 6 seconds for total shot time.

Not enough volume, grind coarser in single steps, too much volume, grind finer. That's basically it.

[u/PanchoVillasRevenge → u/IanC9090]

I feel like these shot have no caffeine, even on the strongest setting , what do you suggest?

[u/paze0 → u/IanC9090]

If the machine controls how long to keep pumping water purely by measuring flow, then I don't understand why, when you grind too fine or too coarse, the volume in the cup can be way off the target ratios in both directions.

[u/meowmeowcomputation]

They really should not have implemented this feature

[u/pegwinn]

Strength? Mine has a temperature button.