Cimbali Jr = sour everytime, why?

Need help with equipment usage or want to share your latest discovery?

#1: Post by SamuraiE »

Dan and others, any help here would be great! I've had my setup, Jr and Jr grinder for 7 months now. I think I have come to understand both machines and how to construct a nice drink.

Since day one all my espresso shots have been sour, never bitter, never once. I played with the settings after the first month and brought boil pressure down to 0.9 bar and same for group pressure. Grind is good, always dose same amount, standard Cimbali double basket filled to top....north/south finger sweep, always tamp the same. Shots pull great 60ml in 30 seconds. Crema 50%-70% at first then settles to about 15ml. Color of shot is fine (dark with specks) sometimes goes blond a little early. Got my bottomless pf last week just to check if my tamp, etc. might have been the problem but it wasn't....pulls are centered and no sprays.

Yesterday I set boiler way up to 1.4 bar just to see if I could burn a bitter shot and moved group pressure up as well. Even without a cooling flush and letting the machine set for 2 hours the shot came out sour again. So now I am thinking this has to be some kind of voltage problem in my house. Perhaps the machine is set to run on 110volts and is only getting a floating 100-110 volts? The folks in France who I bought from had La Cimbali make this machine to fit with Japanese specs and told me it was set to go at 100volts....but come on, over 500 shots and every one sour, what gives?

I am not worthy!

SamuraiE (original poster)

#2: Post by SamuraiE (original poster) »

Should add that I have tried many different kinds of beans and have a Hottop and roast at home with good results so this isn't a bean issue.

I am not worthy!

CafelatStore: home of Cafelat products online
Sponsored by CafelatStore
User avatar

#3: Post by HB »

500 shots, all sour? You have a lot of patience!

Unless the extraction is too fast, I would blame the temperature for sourness. Junior will spit plenty of steam and boiling water with a boiler setting of 1.4 bar after being idle for two hours (mine was set at 0.9 bar). If that's not the case, I suspect a mechanical problem. Have you had a service technician take a look at it? Did you say this machine is new? I ask because we all learned a lesson about scale in Sputtering e61 & HX scale build-up - Cured!

PS: As I mentioned in the review, although the heat exchanger contains super-hot water, the group itself idles below brew temperature. It takes a few flushes / shots to warm up. Unless you take extra steps to warm up the group (see How I Learned to Love HXs in the review), the first shot or two will tend to be sour.

PSS: I don't believe this is possible, but let me offer some additional wild speculation... maybe the water level is very very low and only the tip of the heat exchanger in touching the water. The water level sensor is "f" in the picture below. It is at the lowest point when vertical and the highest when horizontal.

Dan Kehn

SamuraiE (original poster)

#4: Post by SamuraiE (original poster) »

Dan, that was quick! Let me give you a few more details just to see if they mean anything to you. This is a brand new machine and under the drip pan it says:

La Cimbali M21 Jr. S1
100 ac (guess they really did make one especially to match these Japanese specs)
50/60 Hz
Boiler 1: 133 C-0.2 Mpa (2 bar)
Boiler 2: 133 C-1,2 MPa (12 bar)

Are they saying that the boiler should be set at 2 bar? That seems very, very high to me. And why Boiler 1 and 2....I thought this machine has only 1 boiler?

Finally, the boiler fill is set exactly like the one in your photo.

500 shots all sour, but they range in degree of sourness...some quite sour others not to bad....also milk drinks taste fine even with the sour espresso base and those are what we tend to drink the most of anyway. Perhaps I should write to La Cimbali and ask them what they think. Also, since I refused to pay the $8,000 price tag that the Japanese rep in Fukuoka was asking I doubt very much that his service tech the next prefecture over will want to have anything to do with my machine.....alas, I am on my own.


p.s. read you article on the N.C. contest over at CG....very well done as always!
I am not worthy!

User avatar

#5: Post by HB »

I can't comment on the labels as I didn't bother looking at them closely (clearly Junior doesn't have two boilers and the rest of the information isn't pertinent).

Back to the sour shots: I would like a little more detail about the temperature. For starters, is the cooling flush sputtering similar to the video for the Elektra A3? Junior doesn't flash quite as loudly, but you should see a very distinct transition from the "water dance" to a smooth flow. Assuming that's as expected, do you follow the basic steps outlined in the writeup for warming the group and flushing before the extraction? My line of questions are towards figuring out if this is a mechanical issue (e.g., the HX and group aren't heating enough for some reason) or usage issue (e.g., flushing too much).

It would be very nice if you had a thermocouple thermometer to check the in-basket temperature; if that's not possible, the Styrofoam cup technique is worth trying. It shouldn't be hard to measure around 198F if the flush is correct.

PS: I don't think this is at fault, but it's worth knowing that raising the boiler's water level will increase the group temperature.
Dan Kehn


#6: Post by bobroseman »

Until you figure it out, you might try letting the first 20 mL go to waste and just drinking the last 40mL. See if the sour taste is mitigated.

It's just a stop gap 'til you sort out the problem but I think it will work.


User avatar

#7: Post by AndyS »

HB wrote:clearly Junior doesn't have two boilers
1. Service boiler
2. Heat exchanger "boiler."

The heat exchanger has its own (higher) pressure rating.
VST refractometer/filter basket beta tester, no financial interest in the company

Urnex: 100% dedicated focus on coffee and tea cleaning
Sponsored by Urnex
SamuraiE (original poster)

#8: Post by SamuraiE (original poster) »

Thanks for all the good info! Here are my test results, fresh off the wire.

Cut a 1000ml milk carton down a little and stuffed it into a large coffee mug. Using tape, molded the carton to the standard Cimbali pf (with spout removed) and inserted standard double basket (no coffee just ran the shots straight through the double basket and into the carton). Punched small hole through side of carton and inserted my digital thermometer. In other words, pretty much no air entered the holding vessel. According to the standard guide temp should be within 190-204 F or 87.78-95.59 C

So here goes: Machine warmed up 1.5 hours and pulled about 5 or 6 flushes of 5 oz over a 20 min period.

Bar set to 1.3 and 5.5 oz flush before each shot about 2 mins between pulls

1. 87.5 C
2. 89.8 C
3. 88.0 C
4. 89.3 C
5. 91.4 C no flush before this pull just to see what would happen
6. 90.9 C
7. 89.9 C 4 oz flush before this shot
8. 93.6 C no flush and left machine idle for 5 mins (hottest of the session)

changed bar to 1.1 just wanted to bring it down and see what happens...much shorter flush as water dance ended more quickly (this had been the setting for the machine for the last 3 months or so)

9. 84.7 C 10 oz flush before this shot to stabilize the bar pressure (so should probably discount it)
10. 89.5 C this with 4 oz flush
11. 90.0 C also with 4 oz flush
12. 90.3 C 10 min wait between pull/5 oz cooling flush

OK, so what do you think? Temp seems to be within the guidelines albeit on the lower side.
This machine from day one really seems to need a fairly long flush (5 oz) just to get the water calm and smooth out the dance.

Should I crank the boiler way up to 2.2 bar or something crazy like that just to see what happens? Should I go back to 1.3 bar and not flush the machine in hopes of getting results like pull #8 (93.6 C)?

Just to see what would happen I just ran downstairs and pulled a shot in the milk carton to see what the temp is (carton is not preheated so that should take the temp down somewhat).

Liquid Amber espresso beans....just roasted 3 days ago (72 hours rest) with my Hottop, well into second crack. Cimbali double basket full to top...north/south...tamp and 30 sec pour after a 4 oz flush. Nice color and lots of crema.

Temp 78 C.

Taste, first sip a little burnt....then sour. Not undrinkable sour...but sour, again.
I am not worthy!

User avatar

#9: Post by HB »

SamuraiE wrote:OK, so what do you think? Temp seems to be within the guidelines albeit on the lower side. This machine from day one really seems to need a fairly long flush (5 oz) just to get the water calm and smooth out the dance.
Yes, I think we can safely eliminate mechanical issues. It looks like you are overflushing the group. I made the same error during the early days of the review due to my experience with prosumer E61s; the Cimbali Junior still needs to be flushed, but not nearly the same volume or frequency as a prosumer E61. For those unfamiliar with Junior's group, below is a nice diagram from the owner's manual:

Cimbali Junior hydraulics diagram

The heat exchanger is the cigar-shaped tube resting in the boiler water. The thin tubing inside it is the injector coming from the pump. This "dead end" heat exchanger is different than your typical prosumer E61, which is usually nothing more than a section of copper tubing passing from one end of the boiler to another:

E61 group hydraulics diagram

The grouphead is heated by the thermosyphon bringing heat from the boiler (red / blue arrows). Junior's grouphead is directly attached to the boiler by a heavy "trunk" and picks up its heat by conduction. The water in the heat exchanger also circulates heat to it (hotter water rises, cooler water falls). There are practical consequences of these two designs for the barista. The one that's most likely in play for your situation is Junior's "group memory." Because of the heavy trunk, large insulated boiler and heat exchanger, and beefy grouphead, Junior's temperatures are phenomenally stable under a hard load, which is what the machine was designed for. Junior's temperature management is tricky if it is being used intermittently, and worse yet, if you inadvertently overflush a few times, he'll remember. Other machines I've used don't have as a long a thermal memory -- three minutes and most forgive all mistakes. Not Junior.

In the article I described how I programmed the dosing keys to make flushing easier (Big Flush = 120ml, Double = 90ml, Mini Flush = 60ml, Spritz = 30ml). I only used Big Flush once in the morning and the rest are Mini Flushes. Your temperature trials were all preceded by Big Flush+ and likely accumulated some downward thermal memory. As I mentioned earlier, I got caught by the same error and it was Ken Fox and Jim Schulman who pointed me in the right direction, which begins by forgetting what you know or have read about using prosumer E61s -- applying the same regime to Junior will result in consistently sour shots.
Dan Kehn

User avatar

#10: Post by malachi »

Agree with Dan but would also love to hear more about the coffee you're using.
"Taste is the only morality." -- John Ruskin