Shot timing with mechanical preinfusion

[Barabus]

Newbie here with a Mini plus mechanical preinfusion kit added by Chris Coffee. My question is whether or not I should add 6s to the general guideline of 25s-30s for a double shot? My early shots are running a little long, but good. Maybe I should just enjoy and not be too quantitative? Is 6s the general "setting" for the mechanical preinfusion? Should I be aiming for 31s to 36s?

[Endo]

Sorry. There is no clear answer. Depends what you like.

Personally, I dose arund 16g and try for around 30 seconds. I stop the shot when it goes blond, but in general I'm not too hung up on time. I've had great shots anywhere from 30 to 45 seconds with my Mini with p/i.

Can't say I've had much success with the standard 25 seconds though, but that might just be personal taste.

[slo]

As Endo previously said there is no other answer than your taste.

But if you want to get guidance (to start the process of experimenting), these days my shots are between 14 to 16.5 grams with 8 seconds pre-infusion and running 35-40 seconds total. I grind fine and tamp somewhat strong these days, My process varies A LOT, firstly because I like to experiment, I like variety and mostly because I change coffee all the time. But overall I seem to always like the shots that take (much) longer than the traditional 25 seconds.

Up to you. But feel free to share and let us know if you find something good.

[Barabus]

I agree with the observation that 25s is too fast for this setup. I normally get flow about 8s into the pull. My guess is that the mechanical preinfusion is not calibrated that well. It just "is what it is", so to speak. Mine is around 6s and then I see the pressure raise rapidly.

Is this consistent with other Mini owners with the preinfusion kit?

[Endo]

There shouldn't be much variation in the mpi (mechanical pre infusion). It should max out as a function of the chamber volume and pump flow rate. My pressure maxes out at 6 seconds exactly.

As Slo mentioned, my Mini seems to require a fine grind with a good solid tamp (including nutation) and a longer shot if around 35 seconds rather than 25.

I've tried going lighter on the tamp, no nutation, 25 sec shots, WDT, etc..... but it seems to always give me channeling. My opinion is the Vivaldi is more prone to channeling than my 58mm machines (opposite to what they claim). The good news is, it's manageable with some changes to your technique.

[oton]

Newbie here with a Mini plus mechanical preinfusion kit added by Chris Coffee. My question is whether or not I should add 6s to the general guideline of 25s-30s for a double shot? My early shots are running a little long, but good. Maybe I should just enjoy and not be too quantitative? Is 6s the general "setting" for the mechanical preinfusion? Should I be aiming for 31s to 36s?

To be concise with your question, I'm aiming at a minimum of 31s (25 + 6). So yes, I add the 6 preinfusion secs. to the 25 sec. of the "golden rule".

[Barabus]

Thanks for the confirmations. I appreciate the guidance.