Hi All!

Newcomer but longtime lurker here.

I just bought a brand new ECM Mechanika VI Slim about 10 days ago. This is my first time with an E61 machine so I was still getting used to the gauges (previous machine was a Nuova Simonelli Oscar 2). I guess I was so used to using a machine without a readable gauge so I didn't even notice until recently that during extraction my pressure is really low. It maxes out at about 4-6 bars depending on the coffee used but I've never gotten anything higher than 6 bars when there's coffee in the basket. At first I thought it was a gauge problem but when I ran the pressure with a blind basket it was reading 10 bars which is what it's supposed to be set at from the factory. The weird thing is that I'm getting pretty tasty shots and thats probably why I didn't even notice that the pressure was running low during extraction.

This machine comes with a preinfusion function so I thought hmm maybe that's possibly whats causing the lower pressure since for the first five seconds it soaks the puck at about 2bars and then ramps up the pressure but when it ramps up it only reaches about 4-6 bars as I previously mentioned. So I turned off the preinfusion and even without preinfusion I'm still only pulling shots at 4-6bar pressure during the whole extraction. This lead me to try and increase the pressure on the OPV to 12 bar with a blind basket and then see if my pressure ups to 8bar during extraction with coffee. But...when I adjusted the OPV I had to twist the screw about 3 full turns counterclockwise to make any difference and even then it still only read a hair past 10, which I thought was a bit strange and excessive. Another strange thing is when I lowered the lever and let the machine sit for a couple seconds then the gauge was now reading 12 bars which is what I was trying to achieve with the blind basket. So after adjusting the OPV I pulled another shot and even with the OPV set higher I was still only getting 4-6 bars during extraction.

Side notes:
- I WDT, tamp, and use a puck screen so I'm assuming puck prep is not an issue.
- For now I am using a Turin SD40 grinder which has given me pretty good results for espresso and from what I've seen nobody has had any weird pressure issues because of this grinder so I'm ruling that out too.
- I live in Japan and the water here is really soft and I also filter it as well so I know scale isn't the issue.

Any ideas? I guess I'm wondering, should I even be worried if I'm getting tasty shots even with this low pressure?

tjbarista wrote: At first I thought it was a gauge problem but when I ran the pressure with a blind basket it was reading 10 bars which is what its supposed to be set at from the factory. The weird thing is that I'm getting pretty tasty shots and thats probably why I didn't even notice that the pressure was running low during extraction.
Any ideas? I guess I'm wondering, should I even be worried if I'm getting tasty shots even with this low pressure?

Sounds like the machine is working perfectly. And if you're enjoying the shots, that's great, nothing wrong with brewing at 6 Bars, if it produces good results.
You'll need to adjust your grinder finer and/or dose more coffee into the portafilter basket to give the coffee-prep the resistance needed to create more pressure if you want to experiment with the results of brewing at 8.5 or 9 bar.
It's probably best not to mess with the OPV if you've already proven that it's working properly at 10 Bar.

I just experimented with going super fine and choking the machine and I'm still getting maybe max 6.5bar is that normal? I also just checked the flow rate and I'm getting 4oz in 17 seconds so that's not a problem, so I'm just a little confused why its not ramping up to 9-10bar during extraction like I've seen other mechanika slims do.

"Choking" the machine means no flow, or close to it. If you're getting 4 fl. oz. in 17 seconds, that's still very fast.

That's about 120 mL in 17 sec., or about 7 mL/s. The typical vibe pumps are Ulka E5-series. 7 mL/sec is 420 cc/min. A typical pump can't put out more than around 4 bars of pressure and maintain 420 cc/min.



My guess is that you've got a strong pump (getting 6-7 bar at those flow rates) and that your grind is rather coarse for classic espresso.

There isn't anything wrong with low extraction pressures or high flow rates. Those are techniques used by many people making espresso from light-roast coffees, ones typically labeled as "filter".

The first thing I would do is to confirm that the OPV is opening somewhere between 8 and 9 bars with a blind basket in place (the one with no holes in it).

I would then see how you like the coffee as you make the grind finer and finer. People who make classic espresso often shoot for about a 1:2 ratio in about 35 seconds from turning on the pump.

Have you used this grinder with your previous machine? This coffee?

Thanks for the detailed reply! This is my first experience with an e61 machine so I'm honestly really relieved that its a me problem and not a machine problem haha

To answer your last question, yeah I used the same grinder with my previous machine but the Oscar ii doesn't have a pressure gauge so I never really knew what pressure I was brewing at. I have confirmed that I'm getting 10bar pressure with the blind basket in, going to play around with grind size, dosage and try out some different baskets to see how that affects pressure! Thanks for all the help!