Hey everyone.

I was thinking and I've thought about it a couple of times now during a shot. What if I were to turn off the shot after the pump "choked" for preinfusion and let it sit for however many seconds - for fun let's say 5 - would this change anything or would the machine go into full pump once I've turned the pump back on? I guess also a better question is ... Would I need or even want to do this for any real benefit? hahahaha

If you turn off the extraction after there is any pressue in the brew group, and the 3-way valve opens when you turn off the extraction, the release of pressure can be sufficient to "suck" the coffee from the basket and dislodge it completely. It can make a mess of the shower screen as well as result in a very poor extraction, indeed.

A less-risky technique, instead of turning off the pull, may be to manually open the boiler-fill solenoid. This would prevent the pressure from dropping to ambient. Neither method guarantees you a mess, but certainly raises the probability.
-Ed

Or put a toggle switch on the pump and cutoff power to it for a few seconds. The group will slowly depressurize and the 3-way solenoid will remain in the "brew" position.

Or, better yet, if you have plumbed-in E61, use the detent position to preinfuse with line pressure until your heart's content. I've tried various ways of "pre-wetting" and concluded that it helps the forgiveness factor if done for 2-3 seconds; if extended much beyond that, the clarity suffers and ultimately the flavor profile becomes muddy. However, I should add my comments are based on experiments from awhile back, so take them for what they're worth (exactly what you paid for them ).