This is one of the settings on my Gaggiuino.
There is a lot of debate about pressure vs flow profiles.
Pressure = flow x puck resistance.
They are linked.
The early (analog) lever machines naturally understood this relationship.
You pulled on a spring (loaded at 9 bar).
As the lever went up the pressure slowly decreased from 9 bar.
During this time, the flow naturally would also decrease.
And this would compensate for the degradation of the puck over time.
The end result was a great cuppa.
Today, pumped machines keep the pressure at 9 bar even though the puck is degrading.
The result is a increase in flow rate towards the end of the shot with a much more diluted finish.
I think lever machines had it right from the beginning. When you pulled the lever down (in the case of a spring lever) the puck was saturated instantly
(at boiler pressure) reducing the chance of puck unseating, and then a pressure to flow relationship was maintained during the shot pull.
With my E61 machine I'm getting about 7g/sec flow.
It will continue to deliver water to the coffee puck at that rate until it hits 9 bar.
At that point, the OPV will kick in.
Usually the 9 bar level is reached pretty early .. usually at the end of pre-infusion.
The flow rate is probably not 7g/sec. Instead, it will be whatever it needs to be to stay at 9 bar.
Flow is very hard to control.
Resistance is related to the type of grinder, the grind size, roast level, puck integrity, grind solubility, tamp force, distribution, etc
I think that above 10bar, coffee doesn't taste great, so if your focus is on flow
and you accidently touch 10 bar, you risk the coffee failing.
The adaptive setting is very interesting.
Its designed to prioritize the flow rate .... moving it up or down
& adapt it to the chosen grind and dose size..... keeping everything below the peak pressure.
Note that preinfusion is mostly about flow (as there is usually very low pressure).
When discussing flow we usually are focused on the post infusion stage.
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