Group Pressure

[Lynchmeister]

With the advent of home roasting at Casa Lynchmeister, I'm beginning to once again take a close, hard look at the nuts and bolts of my coffee experience at home.

I have a Gaggia Evolution, which reportedly puts out around 15 bar at the group head. Is this too much pressure? After reading the following snippet from a CoffeeGeek review on the machine, I'm curious if this is a real concern or just me splitting hairs...

I recently rigged a brew pressure gauge, and found that the machine was producing 14 bar at the group, which is about 50% more than the ideal. The problem was a seized up expansion valve which was easily poked free due to it's shape. Now it's down to 9-10 bar, and the espresso I'm making now is heavenly. A lot of the harsh flavors I had been attributing to brew temperature were actually because of the immensely high pressure.

I've googled "seized up expansion valve AND gaggia evolution" with no luck. Thoughts on what I might do (or rather, a better explanation of what he did) to reduce to pressure to closer to 9 bar or should I settle down and leave it as is?

 

[coolbluewater]

Around 11-12 should be fine IMO, unless you want to spring for a PID kit.

 

[echelon3]

Actually, it is too much pressure. It's going to be hard to get proper extraction at that pressure, which means that it will be hard to get good espresso out of it.

As a PID controls only the temperature, I'm not sure that would help you.

There was a guy over at the HomeBarrista forums that worked on Gaggia's...I don't go there much so I can't be much help on his name.

 

[coolbluewater]

Evo's have small boilers and flaky expansion valves; a PID set somewhat lower temp will produce a shot that an ideal 8.5-bar and proper expansion valve would, at a normal temp. Been there.
Unscrew and pick it free with with a wire or drill bit, or Saecoparts has replacements, then you should be all set.
Still, a PID makes a huge difference.

 

[Lynchmeister]

Evo's have small boilers and flaky expansion valves; a PID set somewhat lower temp will produce a shot that an ideal 8.5-bar and proper expansion valve would, at a normal temp. Been there.
Unscrew and pick it free with with a wire or drill bit, or Saecoparts has replacements, then you should be all set.
Still, a PID makes a huge difference.

Yes...I think this is moving in the direction I'm wondering about based of that quote I posted above from the CG review. Can you elaborate a bit more on the procedure of doing this?

After reading it again, are you simply suggesting that I remove the expansion valve completely?

 

[Lynchmeister]

Another afterthought. My shots are what most would consider fast and, at times, thin. I know this is at least 90% due to my grind (Hario will be on it's way soon), but it would stand to reason that blowing twice as much pressure through the PF would also be a contributing factor in my 15 to 20 second shots, right?

 

[coolbluewater]

Another afterthought. My shots are what most would consider fast and, at times, thin. I know this is at least 90% due to my grind (Hario will be on it's way soon), but it would stand to reason that blowing twice as much pressure through the PF would also be a contributing factor in my 15 to 20 second shots, right?

Correct.
And yes, remove the EV for cleaning/replacing.

 

[Lynchmeister]

Correct.
And yes, remove the EV for cleaning/replacing.

Aha! That makes sense now.