Help with La Cimbali Jr.

[SamuraiE]

Dan, you out there? I have been using my Jr. for about 2 weeks now and have become more familiar with his ups and downs. I have read your article from the Chris Coffee link several times, even though it is a direct pumbed in machine and mine is not (pourover). Questions:

(1) Seems like the boiler pressure was set by the factory at a peek of 1.1 on the gauge on the front of the machine, at least that is the highest it has ever gone....the cooling flushes needed are quite long indeed. I often must draw a full cappa cup worth of water before pulling a shot just to get a nice smooth stream of water coming out of the pf at the end of the flush and this is not after a long idle rest period. This seems to drop the pressure down to 0.8 or so, should I go ahead and pull the shot now at 0.8, or wait for the unit to go back up to 1.0 or 1.1? If I wait it seems to be too hot again.

(2) A friend has told me he played around and adjusted his brew pressure(?) saying brew pressure is different than boiler pressure. Am I correct in thinking that boiler pressure is responsible for the temperature of the water coming out of the machine? What is brew pressure and where can I adjust it on this machine? Is an adjustment needed? Any advice on this subject would be most helpful.

shots are good but should be much better.....grind and tamp are good....extraction time is dead on.....shots taste sour, bitter (honestly can't tell the difference between the two). Crema is good, especially on the Monkey blend which arrived yesterday from SM. I did pull one shot at 0.9 using the Monkey and it was out of this world, but have had trouble matching it.

thank you

[HB]

DISCLAIMER: UNPLUG THE MACHINE BEFORE MAKING ANY ADJUSTMENTS. ELECTROCUTION IS DETRIMENTAL TO YOUR HEALTH.

I tried boiler pressure settings from 0.7 to 1.3 bar and settled on the original factory setting, which was 0.9 bar in my case (measured from the top of the cycle). You can change the boiler pressure and thus the temperature by turning the 7mm nut atop the pressurestat spring (tighter = hotter):



The brew pressure is indeed completely different than the boiler pressure. Since Junior has no brew pressure gauge, you must use a portafilter pressure gauge, similar to the one below:



A brew pressure of 8.5 bar is a good starting point. Your model (S1) has a vibration pump and presumably uses an expansion valve to regulate the maximum pressure. Jim Schulman explained the mechanics of vibe pump pressure regulation that apply to your machine. I'll defer to Chris' technicians for the specifics, since I had the DT1 (rotary) model and thus don't have any pictures.

Begin by lowering your pressurestat setting and then look to the brew pressure. Once you have the pressurestat setting correct, you can pretty much ignore the boiler pressure gauge. Junior's heat exchanger and boiler are large enough that the position of the needle at any given time is inconsequential for the purposes of pulling shots. The flushing regime I detailed in the guide should get you started, then you can fine-tune it to your tastes and blend selections.

[SamuraiE]

Thank you Dan. I'll send for the gauge and see where it takes me. Will also continue to read through this fine site. Again, thank you for getting back to me so quickly.

Key

[bobroseman]

Thank you Dan. I'll send for the gauge and see where it takes me. Will also continue to read through this fine site. Again, thank you for getting back to me so quickly.

Key

Key,

It seems to me that if your going to measure brew pressure and make adjustments, then you need to know the exact pressure that you have while pulling a shot. Most portafilter gauges measure only the static pressure at the brew head when the by-pass valve has opened. That is not the pressure you are getting when you are brewing espresso. The attached photo is a simple mod I made to the gauge I bought from Chris Coffee. I can adjust the needle valve to allow precisly 2 oz of water to flow in 25 seconds while reading the pressure. On my machine, the resulting pressure is 8 bar, as seen in the inset.

Bob


here it is in use:

[cinergi]

Bob,

what hardware store did you get all those fittings from? They even had the needle valve?

Thanks.

[bobroseman]

Bob,

what hardware store did you get all those fittings from? They even had the needle valve?

Thanks.

Hi,

I brought my portafilter to Home Depot and picked up all of the parts, loose fitting them on the spot.
The only thing I brought in was the pressure gauge. Don't forget the teflon tape.

Bob

[cinergi]

Bob,

Do you know if this mod will work with Greg Scace's new thermofilter?

Thanks.

[barry]

Bob,

Do you know if this mod will work with Greg Scace's new thermofilter?

Thanks.

you won't need the needle valve.... and several other connectors.

[cinergi]

Won't I need the needle valve if I want to control flow? And if so, I would assume I would need to remove the filter.

[barry]

the terminal cap has a restricting orifice in it.

if you remove the filter, your needle valve will likely plug up at some point.

[bobroseman]

The Scarce device isn't really required. I have a 5 foot long 36 gauge T junction teflon coated wire which fits neatly over the edge of the PF and into the basket space. For repeatability I suppose that it could be anchored but I haven't bothered.

The only problem with this set up is that you have a PF full of water which is thermodynamically different than one filled mostly with coffee. I have chosen to ignore the difference in my tests. My results on the La Spaziale are very similar to Greg's results on the La Marzocco.

Bob

[gscace]

The Scarce device isn't really required. I have a 5 foot long 36 gauge T junction teflon coated wire which fits neatly over the edge of the PF and into the basket space. For repeatability I suppose that it could be anchored but I haven't bothered.

The only problem with this set up is that you have a PF full of water which is thermodynamically different than one filled mostly with coffee. I have chosen to ignore the difference in my tests. My results on the La Spaziale are very similar to Greg's results on the La Marzocco.

Bob

The test conditions are quite different between the two measurement methods. In your method how is water flow rate controlled? Several years ago, I made a bunch of measurements on Rancilio Silvias using T type thermocouples snaked up through the filter basket with the probe resting on top of the coffee cake. It was a ton of work and couldn't make constant duty cycle measurements. The thermofilter makes it almost trivial.

-Greg

[bobroseman]

The Scarce device isn't really required. I have a 5 foot long 36 gauge T junction teflon coated wire which fits neatly over the edge of the PF and into the basket space. For repeatability I suppose that it could be anchored but I haven't bothered.

The only problem with this set up is that you have a PF full of water which is thermodynamically different than one filled mostly with coffee. I have chosen to ignore the difference in my tests. My results on the La Spaziale are very similar to Greg's results on the La Marzocco.

Bob

The test conditions are quite different between the two measurement methods. In your method how is water flow rate controlled? Several years ago, I made a bunch of measurements on Rancilio Silvias using T type thermocouples snaked up through the filter basket with the probe resting on top of the coffee cake. It was a ton of work and couldn't make constant duty cycle measurements. The thermofilter makes it almost trivial.

-Greg

Greg,

In the picture earlier in the thread you will see there is a needle valve which can be adjusted to permit 2 oz of water to flow in 25 seconds. The pressure can then be read.

However when it comes to measuring temperatures, my set up has problems. One is that the placement of the TC can vary and, two, there is no coffee in the basket and so the thermodynamics are wrong. As I stated, I have ignored these things. Your method might eliminate those problems.

When I said that your device wasn't required, I meant in conjnction with mine. I'm sure that your device works quite well as a stand alone.

Still, my curves are remarkably similar to those that you achieved on the La Marzocco, if memory serves.

Bob

[barry]

Still, my curves are remarkably similar to those that you achieved on the La Marzocco, if memory serves.

which means exactly nothing.

[HB]

which means exactly nothing.

My thoughts exactly, but for a different reason.

[bobroseman]

Still, my curves are remarkably similar to those that you achieved on the La Marzocco, if memory serves.

which means exactly nothing.

I am not comparing the La Marzocco Linea with my La Spaziale S1. Heavens no! I wouldn't presume. I intended to compare two temperature measurement approaches not two machines.


Greg's curve here:


reminded me of my curve here:


However, even at that, I am quick to point out that Greg has given this much more thought than I have. My humble contraption was intended to allow me to measure pressure. I quickly became discouraged in trying to measure temperatures. I took a lot of data but was able to come to no meaningful conclusions as a result.

Over and out.

Bob

[barry]

I am not comparing the La Marzocco Linea with my La Spaziale S1. Heavens no! I wouldn't presume. I intended to compare two temperature measurement approaches not two machines.

nothing wrong with comparing machines. my objection was the comparison of methods, followed by the comparison of machines, as if to say the similarity of curves validated your <admittedly flawed> method. comparing the curves means absolutely nothing, other than, perhaps, for us to say, "hey, look! curves!"

btw, http://www.angry-bunny.com is my site, not greg's. check out the madeleine pages for baby girl photos!

--barry "need to stop messing with espresso and update her pages"

[bobroseman]

I am not comparing the La Marzocco Linea with my La Spaziale S1. Heavens no! I wouldn't presume. I intended to compare two temperature measurement approaches not two machines.

nothing wrong with comparing machines. my objection was the comparison of methods, followed by the comparison of machines, as if to say the similarity of curves validated your <admittedly flawed> method. comparing the curves means absolutely nothing, other than, perhaps, for us to say, "hey, look! curves!"

btw, http://www.angry-bunny.com is my site, not greg's. check out the madeleine pages for baby girl photos!

--barry "need to stop messing with espresso and update her pages"

Yes, I see that it is your site. And a fine site it is, too.

Before pleading guilty to fuzzy headed thinking I went back and reread the description of the Scarce device. I see a lot of similarity. Both use T-junction probes, both restrict water flow and neither measures the actual temperature above a real coffee puck. ( The question of t-probe placement error between the two devices is addressed by the J probe (Banjo Bolt) comparison.) I also used a special insulator (a cut down sponge) but I can't claim that it mimics the thermodynamic characteristics of a coffee puck.

But even so, you can't compare measurements, both taken on uncalibrated instruments. So, I retract my statement. I am no longer struck by the similarity of the measurements. In fact I am somewhat bored by the similarity. I am reminded why I quit measuring temperature and ultimately resorted to actually drinking the outflow in order to set my temperatures.

Thanks for putting me right.

Bob

[barry]

ultimately resorted to actually drinking the outflow in order to set my temperatures.

DING DING DING! We have a winner!

[bobroseman]

ultimately resorted to actually drinking the outflow in order to set my temperatures.

DING DING DING! We have a winner!