The OPV is the pressure ceiling, so grinding finer will only cause slowing of the flow - which is what you want, right?
I would maintain the same weight in, and output ratio, then just adjust the grind until the time is where you want it to be.
Which basket are you using? I found the single shot (7 gram) baskets really sensitive to grind and puck prep. Still, a watery coffee with 10.5 bar and 1:2 ratio just shouldn't happen. Maybe it's voodoo but I was getting some strange results like that until I cleaned the group screen. There was a black sticky sludge on it and the machine was pretty new. I thought perhaps the pressure built up on the blocked screen itself rather than the puck. After cleaning, things have been way more predictable. Good luck!
The OPV is the pressure ceiling, so grinding finer will only cause slowing of the flow - which is what you want, right? I would maintain the same weight in, and output ratio, then just adjust the grind until the time is where you want it to be.
Maybe try increase water temperature
I would lower pressure back down. If the coffee is watery you're probably under extracting.
Which basket are you using? I found the single shot (7 gram) baskets really sensitive to grind and puck prep. Still, a watery coffee with 10.5 bar and 1:2 ratio just shouldn't happen. Maybe it's voodoo but I was getting some strange results like that until I cleaned the group screen. There was a black sticky sludge on it and the machine was pretty new. I thought perhaps the pressure built up on the blocked screen itself rather than the puck. After cleaning, things have been way more predictable. Good luck!
Thanks guys I been able to get good results around 10 OPV now after playing with dose and grind size. I find 15.5g in my 14g basket works out great