Tonefish wrote:I went back to my video on that last debit measurement and it was a full 16s out of 30s until the flow settled down from spitting steam (again, my altitude boils at brew temps). So now I needed a pm pull so I ran the flush for one minute during warmup (145F group) and I also captured the PI drain flush at the end. I got 378 ml from the screen (in 60s) and 37 ml from the PI drain.

You're a man after my own heart!
OK, quick recalculations, given the updated data:
-Water debit flow rate: 6.3mL/s @3.5 Bar
-Pump flow rate @ 3.5 Bar: 415mL/minute (Shower screen flow plus PI Chamber volume)
-Deviation from pump curve: ~1 Bar (from Ulka curve)

This seems totally within reason given the check valve, HX injector and other impediments to the pump flow, so I'd say your pump is doing just fine. It also wouldn't surprise me to see that the pump performs a little off efficiency at your elevation...

And the results:

So, I'm interested in your results (pressure measurements in post 1), because the average shot has a flow rate that starts at water debit flow that drops precipitously as the headspace is filled and the puck is saturated. The PI chamber drops this flow into the puck even more by limiting the applied pressure. But let's say it drops to 0.5mL/s and then climbs as the puck erodes, we should see some differential between the Lelit gauge and the group gauge throughout the shot and it should be increasing up until the end of the shot. One thing that would be fun would be to plot the difference between your two gauge readings (while there is one) and cross it to the pressure drop plotted above and see what the theoretical flow rate is before the two pressures overlap...

Cheers and happy Father's day to all the dads reading this!!!

-Jake