I'm working with a Faema E92 Elite 4-Group. And I've notice that everytime I'm pushing a button for a shot, the meter in the gauge (right under) goes to 10 bar.
Now I've read somewhere that the bar should be at 9 for extracting espresso.
Is it normal, with a Faema machine, the bar in the gauge is 10 instead of 9 with every shot?
The machine has one big boiler for all 4 groups and the steampipes.
Thanx for your feedback
Not familiar with that machine, but the same basic principles apply to most machines. Yes 10 bar pressure is a bit high. I prefer to keep ours brewing in the 8 bar range and get excellent results with that.
Does this happen regardless of your grind fineness, tamp pressure, etc?
Do you have any idea what the incoming water pressure is before it goes to the pump?
Try putting in a blind basket and see what happens with the gauge. Could be the gauge is off a bit or maybe the pump pressure needs to be reduced...
Ultimately taste/texture of the espresso should trump all else. Are you getting what you'd consider great extractions from it at this point or does it seem off a bit?
The easy answer:
The target pump pressure at the gage is about 9 bar for most machines in factory configuration. Since this pressure is a combination of incoming building water pressure and machine pump pressure, variations in building pressure can cause this to drift from time to time. This pressure is typically pretty easy to adjust, by carefully turning the brass screw on the pump head with the pump running. There may be a locknut on it to keep it from vibrating, so if its tough to turn you may have to loosen that first.
PLEASE NOTE that this screw will come all the way out if you back it out far enough, spraying water everywhere and potentially misplacing the little screw underneath, so proceed slowly and carefully and stop if you start to see water seeping around the threads.
The hard answer:
The actual extraction pressure at your groups will be somewhat lower than this. A group-mounted pressure gage, like that on a Scace 2, can tell you exactly what you are getting at the group. Extraction pressure is one of the variables that you may wish to play with to get different results from your espresso. If your roaster or someone familiar with your coffee has a particular pressure recommendation and your tech has access to a Scace 2, you may want to tweak this.
Regardless of what course you take, taste your espresso before making any changes. Once you've changed your setting and dialed-in to the new pressure, decide whether you've improved things or not.
FWIW, I always adjust machines to read 9 bars at the gage.
Most of the gauges on these machines are pretty innaccurate. I mean, they're close, but they are as close as the lil dial gauges that you use to steam milk with. Close, but I wouldn't do anything but Kentucky windage with it. See if you can get your hands on a Scace II to get more accurate results.
I have a modified Scace I that has a +/- .1 Bar manometer, and it shows that my Astoria's on-board manometer is off by almost a Bar on the high side.