Hello everyone, I just bought a Mini Vivaldi and I am having some issues with pulling the perfect shot due to pressure variation during the shot. When the shots take 35-40 seconds the pressure goes to 8.5 - 9 then it slowly decreases as the shot is pulled. The volume extracted is around 1.5 to 2 ounces and the coffee is a little bitter. I tried tapping the pf, however, i have the same issue. What I noticed is that when the shots take longer the pressure is stable, however, when the shots times are shorter, 25 to 30 seconds the pressure wiggles around 7.5 and I get squirts which are really annoying. It appears that the pressure directly correlates to the flow rate, thus when the coffee is put in the pf and the flow rate is slower at the beginning of the shot, the pressure remains higher, however, as the shot is pulled and the flow rate increases, the pressure drops and squirts appear. Here is some info I pulled from this website regarding the Mini Vivaldi's vibration pump "unlike vibration pumps, which put out their maximum pressure for a given resistance and rely on an expansion valve for pressure regulation, a rotary pump puts out the same pressure independent of the flow rate". I wonder if this a limitation of the Mini Vivaldi and if I can never get to pull the perfect shot, 25-30 seconds with the Mini Vivaldi.

You have something strange going on, the pump should be amping up to 9 and sticking there. check out the info available here: http://s1cafe.com/

Christian,

Welcome to HB.

What does you pump read when you insert a blind basket and simulate pulling a shot for 30 seconds? Hint: it should ramp up to brew pressure as set by your OPV (expansion valve) and sit there for the duration. I believe page 19 of your owner's manual will cover how to adjust this pressure to your liking.

Also, make sure the tank is properly plugged into the attachment to the machine. If you are using the in tank water softener, make sure there isn't a kink in the hose. It also wouldn't hurt to make sure the o rings on the male end of the connection between the tank and machine are still soft and flexible. If they become hard and brittle they might not create a tight enough seal to maintain constant pressure.

This sounds suspiciously like a coffee issue. It's freshness, grind, and/or distribution. Use fresh roasted and fresh ground coffee, 14 grams in the double basket, distribute and tamp properly and I bet you won't have the problem. Of course, check it out with a blind basket first. The answer to your question is that it's unlikely to be the pump. This pump is quite capable of giving you good, spritz free shots.

Thank you so much for the input. When I insert a blind basket the pressure ramps up to 9 bars and stays there, no wiggle. I will try some fresh coffee today. I also got the calibrated tamper, trying to take out one variable.

I tried fresh coffee, used the espro calibrated tamper, same issue. I took the machine in and the tech adjusted the pressure to 11 bars, now when I pull the shots the pressure is fairly stable around 9. Is this normal, or should I adjust the pump pressure back to 9?