jim_schulman Senior Member Joined: 19 Dec 2001 Posts: 3,772 Location: Chicago Expertise: I live coffee
Posted Tue May 10, 2005, 1:16pm Subject: Contemplating modifying your machine? PID, Pressure Mods, etc. Please read this
In the distant pre-Coffee-Geek days, the people who did this had considerable prior experience with their machines and did their research. The availability of the Coffee Geek forums has made such modifications a lot easier. Nevertheless, someone inexperienced with espresso making or their machines can easily get poor results.
Here are what I think are some minimal espresso skills and machine knowledge you should have prior to doing these projects:
In general, you should be able to make 5 shots in a row with the same time & volume, and very close in taste and crema, before making any sort of change to your machine. You simply won't be able to tell whether it's made a difference unless your shots are consistent. When you make a modifications, you are necessarily comparing before and after; so your technique has to be solid.
If you are contemplating PID-ing: Have a thermocouple and know how to measure shot temperature. Know how to change the temperature on your machine or hold it stable by manual techniques, and have a good idea how shot temperature variations affect the taste.
If you are modifying the pressure, know what to expect. That's basically very little unless you are making ristrettos or singles on very out of whack vibe pump machines. You can get in the ballpark for that fix by measuring the OPV run off; for any sort of precise adjustment, you need a pressure gauge. The taste differences that ensue from small precise adjustments are subtle; and if your shot making is at all variable, the differences you will taste are guaranteed to be imaginary.
The real improvement in shots comes from being skilled enough to pull consistently, and to knowing enough about espresso extraction and your machine to vary the extraction parameters manually. Once you've reached this point, modify away! But know you'll only get comparatively minor improvements.
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