Been playing around with PI times. Yesterday, pulled some shots and refracted the results using a light Columbian roast which came out at a smidgeon above and under 20% - no sourness. PIs for shots were in the 15-18sec range.
Wanted to see what happened if I ground even finer. Pulled a couple of shots where PI times were 24 sec and 32 secs to first drops. First shot completed in 43 secs, second in 53 secs. PI pressure is just under 2 bar. Ratio pulled was 1:2ish.
Taste-wise, yesterday's shots had balanced acidity - lots of tangerine - no lingering sourness. Today's shots weren't markedly different - any acidity present in yesterday's shots even more muted.
Because the Evo Leva's group is independently heated via elements, this means, once water for the shot is pumped into the group, the brew boiler plays no further role, temperature-wise. Water in the group chamber is controlled accurately via the group heater elements. But is this important?
With a conventional lever, no heat goes into the water in the group chamber once it has been filled. Shot is reliant on the residual heat of the large group mass to retain brew water temperature. This isn't necessarily an issue if your PIs are short but once you go long - well into double seconds, there will be a marked drop in temperature both in PI time and total shot. So with the Evo Leva, you have another variable to play with. With lighter roasts, the received wisdom is higher extraction temps which you can do easily by raising the group heater temps. Would seem from the above, by gentle pre-infusing over a much longer time, you can get similar results by not hiking shot extraction temp.
All this is need of further testing and it will be great when more Evo Leva owners get theirs and start posting their findings. Looking forward to a user knowledge base developing. What is abundantly clear, Evo Leva can be a simple and forgiving to use as you want as well as offering the ability to play around and adjust to personal preference.
