La Cimbali M31 Bistro problems

[nickmupp]

Hi all first post on forum.Bought a second hand M31 about 6 months back and after a couple of months tried to fine tune it.I increased portafilla presure in the hope that more pressure would extract more coffee from the grind.Big mistake.My coffee now is clearer and weaker.At the same time i adjusted the grind,and now not sure which is most at fault.I've watched many vids on youtube at flow rate and end result and mines way off the mark.I know it was my fault its all gone the way of the pear,but i would be grateful for any help to get back on track.What should be the presure on my dial for ideal flow rate and how too get the perfect grind.Many ThanksNick

 

[eldub]

I've been reading up on this very topic today. 8.2 to 9 bars, maybe?

Tamp the puck but don't knock it against anything between tamping and schlamming it home. Knocking the porta-filler allows water to go around the puck. A soft center might allow a pit to form and the water can fail to saturate the entire puck.

lw

 

[shadow745]

The "standard" thinking has been 9 bars for quite some time. Personally I like lower pressure, more like 7.5-8 as that gives me the flow, texture and taste I like. Of course it's easy to think higher pressure would extract more flavor. However that usually leads to channeling which will give you a thin/clearer shot because the puck is being fractured and water passes through those fractures instead of fully saturating the puck for even flow.

For the sake of starting over adjust your flow to 8.5-9 bars and then tweak your grind and dose until you get the flow, taste and texture you're looking for. Don't worry too much about tamp pressure, just keep it consistent. Also keep your dose as consistent as possible and be sure to use FRESH coffee or you will be chasing your tail.

There is no such thing as a perfect grind setting as all coffees/grinders are a bit different and you will need to make daily changes as the coffee ages, etc. Just too many variables to even think one setting will work all the time, even though many people make that mistake.

 

[CCafe]

The real problem with setting your pump pressure lower then 9 bar is when the machine goes to fill the boiler mid shot or you turn on the second group to start another shot. Each of these scenarios will result in about a .5 bar drop in pressure. .5 bar isn't a lot so its not a big deal but if your trying to fine tune you may want to shoot for 9 bar to start off with.

The real question here is, is your gauge accurate? Most older machines the answer is generally no. I would purchase a portafilter with built in gauge to make sure your pressure is dead on. The second issue you may have is adjusting the pump. If its original then it might be scaled to a point that turning the adjustment screw won't do anything. The easiest way to fix this is to replace it with a new Procon pump. You can tear it down and try to descale the pump but chances are your only going to do more damage.

Now assuming all this is working the next thing your going to want to check is to see if your expansion valve is running right. If its set to low or isn't working at all you'll know pretty quickly. Put your pressure gauge portafilter in the group. Remove the drain tray and turn on the group. Look down in the drain cup and see if water is weeping out the back hole. If it is and your at 9 bar then you'll have to adjust your expansion valve. Normally we set it to weep 1 drop a second at about 11.5 bar.

There are a lot of little things you need to know are running right in the first place before you can assume your machine is running properly to make a good shot. I might suggest if you don't have the skill set to do this to call a service rep in your area. You can PM me after this post and I'll send you the phone number for the Cimbali Importer/Distributor for your area. Its a good idea to let them first go over your machine to make sure its ready to do what you bought it for. Otherwise you could just be spinning your wheels for no good reason and burning yourself out in the process.

 

[shadow745]

I've extracted from 2 groups while running a handwash sink with no drop in pressure... the ShurFlo just pumps harder to keep up and all is good and relatively smooth.

9 bars may be a good starting point, but it's overrated as is tamp pressure, time, volume, etc.

 

[eldub]

From an article CC posted earlier...

When Luigi Lupi (an expert barista working with Elektra at SCAA 2005 and pictured below) was approached by a small contingent of consumer members, he was quizzed as to the role tamping played in his profession. He shrugged and produced the same quality shot he had produced moments earlier without tamping at all. Speculation in response to his effort ran the range of commentary, from simply crediting his experience to whether or not he had secretly tamped the coffee out of view in some stealth-like manner before mounting the filter.

Espresso Machine Design

 

[shadow745]

I've watched YT videos of some taking as long as 10 mins. to grind, dose, distribute, tamp and pull a double. Most of that time was spent on distributing and tamping. Some will tamp, ding the portafilter with the tamper, tamp more, ding again, etc... accomplishing NOTHING but slowly damaging the soft brass most portafilters are made of. I've even watched people tamp while holding the portafilter/basket mid-air.

I do tamp, but I like to grind a bit finer and tamp less, which is 10-15 lbs. Gives me much better results than grinding coarser and tamping harder. Main thing I look for is even puck thickness and a good sidewall seal. In a commercial setting there is no reason to take more than 15-20 seconds to grind, dose, distribute, tamp and lock in. Maybe less with a really fast grinder.

 

[nickmupp]

Many thanks for all your advice.Will set the bench mark at 9.0 bar and then maybe fine adjustments to the grind.I only have a single spout portafilter at present.So will search the web for a dual spout maybe with a pressure gauge fitted.Early searches have come back with nothing.But will try againMany Thanks

 

[shadow745]

You can attach a pressure gauge to any portafilter, just remove the spout and attach to the threaded portion of the portafilter. Double/single makes no difference.

 

[CCafe]

You can attach a pressure gauge to any portafilter, just remove the spout and attach to the threaded portion of the portafilter. Double/single makes no difference.

That might not work for him as some Cimbali's use a different portafilter. There are a few out there that have a square bottom where the spout is connected and have 2 screws that hold it on.

 

[shadow745]

OK I had no clue Cimbali had to be the odd one in the bunch, lmao... There is probably an aftermarket portafilter that will fit Cimbali groups that could be used for this application. OTOH if he is going to go through this much trouble, why not simply replace the pressure gauge on the machine? Surely couldn't be too difficult or expensive...

 

[nickmupp]

Sadly thats my one

 

[CCafe]

Don't be sad, I rather prefer that style. Lets just assume your machine is producing 9 bar. Since that is working fine I would highly suggest you go take a look at your grind. After the machine the grind is always the 2nd thing to look at.

 

[shadow745]

I'd have to say the dose is of equal importance and often overlooked when inconsistencies arise.