You are probably better off not touching the PID settings while you are still learning the machine, but if you want to venture down that path you should read up on some of the material over at CoffeeTime (sponsored by Bella Barista). Bella Barista is the original distributor that brought this machine to market by working with Izzo so you can find details about the original design ideas.

Here's a link on how to adjust the PID programming, written by the owner of machine #2.
http://coffeetimex.wikidot.com/izzo-ale ... d-settings (registration required)

Here's a link on how to adjust the brew temperature offset:
http://coffeetime.wikidot.com/izzo-alex ... t-settings

Also for reference, an overview leading to the first prototype machine:
http://coffeetime.wikidot.com/izzo-alex-duetto

Jeepngo's 15amp mod, which eventually gets incorporated into the formal design via Chris's Coffee.
https://www.coffeegeek.com/forums/espre ... 685&Page=1

haunce wrote:While it lacks bad flavors like sourness and bitterness, the one distinct flavor is "lightness". Maybe I'm confusing this "lightness" with "muted"? I don't know.

Maybe you would like the results better or find more distinction between coffees if you brewed a more concentrated espresso? Higher brew ratio: less water, more coffee. Nothing wrong with that; taste is personal. It's an espresso idiom popular enough to have earned its own name, as you know: ristretto. Also see Espresso 101: How to Adjust Dose and Grind Setting by Taste.

Preinfusion: pressure during preinfusion is never zero, or no water would flow; it's equal to supply-line pressure, typically 2 bar or more, though I don't see very substantial penetration of the puck (in <10 secs) until ~3 bar. Once coffee grounds are wetted, they are extracting, so this time counts significantly (perhaps 100%) toward total shot time. When you add substantial preinfusion time, your pump-on time will be much less, in part because the extraction has a head start, and in part because the pump-on flow will be greater sooner than if you had skipped preinfusion (in my experience). From what I've seen, in bars and at home, 15-20 seconds pump time is more likely after substantial preinfusion time. For me, the main benefit of preinfusion has been less channeling and greater consistency, especially when brewing singles.

Setpoint/Displayed temperature offset: on the Duetto is as probably as meaningful as it can be, given environmental influences: ambient temp, air flow, how tightly the cups are packed on the tray, whether the cup tray is on, whether the case is on, etc. I think the factory chose a good middle-of-the-road value, meaning rarely exactly correct in real time, but on average realistic under typical conditions.

Short-term variation in display temp: means little in terms of overall boiler temp, vanishingly little in terms of anything you will see at the group. If you see wilder deviations in one boiler temp, you hopefully just have a thermistor going bad, as happened to me.

Pre-flushing: as they say, let your taste be your guide, but I've seen no benefit - zero, unless inventing rituals becomes an end in itself. I load and brew. I set my temp to give me the taste I want, and I get it first shot, second, ... etc. I flush only to clean.