Flow rate of a rotary pump espresso machine

[cannonfodder]

Does anyone know what the min/max flow rate for a rotary pump espresso machine is? I am looking for the unrestricted flow rate at 9 bar.

[another_jim]

"Water debit" -- the first 10 second's flow from the group, including the boiling, bubbling water, should be between 60 to 90 mL, with 75 mL optimal. But this includes all the restrictions in the flow (gicleurs, etc), and is based on not destroying the puck with too much or choking the shot with too little flow.

I don't know about the highest 9 bar flow a rotary can do; it probably depends on the pump's size (i.e. presumably less for the small groups on 1 and 2 groupers, more for the large ones on 3 and 4 groupers). Procon and Fluid-O-Tech probably have their pump curves up somewhere.

[HB]

I am looking for the unrestricted flow rate at 9 bar.

In espresso terms, I think the short answer is "a lot". Procon's Capacities & Horsepower lists the maximum more precisely. I've never needed this little piece of trivia... why do you ask?

[cannonfodder]

That Faema I just finished rebuilding pumps a lot of water, and fast. I was wondering if it was flowing too much. After a flush, no spitting and sputtering, I get 4oz from the shower screen in 10 seconds. Does that seem reasonable or is my group jet too large? The pressure ramp is very fast but I am use to a little Isomac.

I am still learning so I still question. This being my first two group, 220v, rotary pump with a ½" regulated water supply, I am still learning the machine and want to make sure I rebuilt it correctly.

[HB]

After a flush, no spitting and sputtering, I get 4oz from the shower screen in 10 seconds. Does that seem reasonable or is my group jet too large?

I just measured the (rotary pump) Vetrano and it was almost three ounces in 10 seconds. Sorry, I don't have an LM handy to measure, but it sounds like you're at least in the ballpark.

[AndyS]

That Faema I just finished rebuilding pumps a lot of water, and fast. I was wondering if it was flowing too much. After a flush, no spitting and sputtering, I get 4oz from the shower screen in 10 seconds. Does that seem reasonable or is my group jet too large? The pressure ramp is very fast but I am use to a little Isomac

I think it's too much. You want to be in the 60-90ml ballpark. This will accomplish a style of preinfusion ("gradual infusion") which will make it easier to produce good shots.

[cannonfodder]

Sounds good. Correct me if I am wrong, but the group jet is what regulates the water flow to the dispersion screen. The larger the jet, the more water you flow, just like the jets in a carburetor.

An espresso group actually has a lot in common with a carburetor. The gas tank would be comparable to the water reservoir; they both have a pump and the larger the engine the larger the pump and supply line that are needed. The bowl would be the equivalent of the expansion chamber; the jet regulates the volume of liquid into the group, or intake manifold. I would not want to drink a shot from an exhaust pipe though.

[AndyS]

Sounds good. Correct me if I am wrong, but the group jet is what regulates the water flow to the dispersion screen. The larger the jet, the more water you flow, just like the jets in a carburetor.

Sounds about right.

An espresso group actually has a lot in common with a carburetor. The gas tank would be comparable to the water reservoir; they both have a pump and the larger the engine the larger the pump and supply line that are needed. The bowl would be the equivalent of the expansion chamber; the jet regulates the volume of liquid into the group, or intake manifold. I would not want to drink a shot from an exhaust pipe though.

Four group machine is like a 4-barrel carb?

[cannonfodder]

I think it's too much. You want to be in the 60-90ml ballpark. This will accomplish a style of preinfusion ("gradual infusion") which will make it easier to produce good shots.

Interesting, part of the reason I ask is because I have been having fits pulling decent shots. I have just been attributing that to the handle side of the portafilter and having to adjust to a new machine. I can pull a pretty darn good shot from my Isomac and my lever but this machine is in a different class.

When I rebuilt the groups, one of the dispersion disks had a crack in it so I ordered a new one. When I received the new disk I was surprised at how much smaller the openings around the disk were. I attributed that to years of use eroding the brass. I got to thinking, and wondering if the group jets had suffered similar erosion over time. Jets are cheap, under $2, so I ordered a new one for the sake of trying along with a couple of ridge-less LM baskets. I am assuming that the new jet would reduce the flow rate provided the old one has opened up over time?

[AndyS]

Interesting, part of the reason I ask is because I have been having fits pulling decent shots. I have just been attributing that to the handle side of the portafilter and having to adjust to a new machine. I can pull a pretty darn good shot from my Isomac and my lever but this machine is in a different class.

When I rebuilt the groups, one of the dispersion disks had a crack in it so I ordered a new one. When I received the new disk I was surprised at how much smaller the openings around the disk were. I attributed that to years of use eroding the brass. I got to thinking, and wondering if the group jets had suffered similar erosion over time. Jets are cheap, under $2, so I ordered a new one for the sake of trying along with a couple of ridge-less LM baskets. I am assuming that the new jet would reduce the flow rate provided the old one has opened up over time?

People play with jet sizes. 0.6mm seems to be popular with obsessive artisan baristas (which is what I aspire to be)!

I'm told 0.6mm is also the size orifice used in the LM GS-3, and the GS-3 has an pretty low water debit around 60ml/10 sec. It has a reputation as an easier machine to pull shots on, and the low water debit is one important factor, I believe. Along with exceptionally good water dispersion in the group, great temp stability, stainless brew path, etc, etc....

[cannonfodder]

Four group machine is like a 4-barrel carb?

A better analogy would be my Kawasaki. Four cylinders with one single barrel carb per cylinder. You want to talk about a tuning nightmare, try synchronizing 4 carbs to the same flow. But when you get it right, hold on because the wind get pretty strong at 160mph, not that I would ever break the law and speed.

[RapidCoffee]

I just measured the (rotary pump) Vetrano and it was almost three ounces in 10 seconds. Sorry, I don't have an LM handy to measure, but it sounds like you're at least in the ballpark.

I'll confirm that on my Vetrano: just measured 5.5oz in 20sec (no PF).

[cannonfodder]

I'll confirm that on my Vetrano: just measured 5.5oz in 20sec (no PF).

Sounds like my jets need tweaked. I am getting almost twice that flow rate. Maybe my shot problems are on the machine side of the handle, sounds like a good excuse for now.

[Rosemary]

My flow rate on my 15yold Cimbali Jnr is also about double! I assume these flow rates are still relevant even though it has a vibe pump? Does this mean I also should be changing the group jet and/or group jet filter?
I haven't worked out how to access these. Is there any simple explanation anywhere. ( I have looked at the exploded diagram on coffeeparts but I couldn't see how to get to this!)


Many thanks

Rosemary

[erics]

Silvia (what a sweetie) just did somewhere between 3.33 and 3.50 ounces in 10 seconds. She has an orifice also and I seem to think it is about 1.0 mm.

I thought the only function of the orifice (0.6 mm or thereabouts) in an E61 machine was to control the preinfusion??

Cannonfodder - you needs one of those adjustable floating ball flowmeters that were made for solex and weber carbs for your K machine. And - could you point me to the link of the E61 animation - I have searched to no avail.

While I fully agree with Jim S's definition of water debit although I would increase the flow a little, does anyone know the origin of the term "water debit" as it relates to espresso machines? Is it used to give some indication of preinfusion qualities or pump output under zilch load or both? Illy shows nothing on "water debit" and google only shows forum discussions.

Eric S.

[HB]

And - could you point me to the link of the E61 animation - I have searched to no avail.

It's linked from the Resources page.

[erics]

I thought that Cannonfodder originally provided that link but in any case, she is a tired link now. I did get to see it once but then that was then and this is now.

http://www.benissimo.nl/e61/

I would find it fascinating (sorta similar to AndyS's profiling) to see what a change in orifice size would do to taste assumming I could keep everything else relatively constant.


Eric

[another_jim]

Andy and I are old hands in this. I think this:
http://tinyurl.com/ffeoo
is the link to the original discussion on alt.coffee

[cannonfodder]

I thought that Cannonfodder originally provided that link but in any case, she is a tired link now. I did get to see it once but then that was then and this is now.
Eric

Wasn't me, but I do remember it.

It will be interesting to see what changes after I swap out the jets. I don't have anything as fancy as a data logging pressure transducer. So I will have to rely on my papillae (taste buds), shot glass and timer. I don't have any means to map the pressure profile.

[cannonfodder]

So if I understand correctly, having to large of a water jet would give me to high of a water debit. That prevents me from getting a proper preinfusion and hence an even extraction. Because of my excessive flow rate, the puck is getting hammered and I am getting an uneven extraction.

On my Isomac, I get two distinct water flows and pressure readings on my brew gauge. Once I engaged the pump, I would get a slower trickle from the group, the pressure would rise to about 5 bar and hold there for 6 or 7 seconds. Then the pump sound would deepen, as if it was encountering some resistance, and the pressure would increase to 9 bar.

That delay was my water debit (preinfusion) phase as the expansion chamber filled to capacity. The audible change in the pump would be when my expansion chamber was full and the pump started to encounter some resistance. If I were to measure the water vs. time, I should be getting around 34ml for my 17 gram double in that preinfusion stage. Your optimal situation would be 34ml in 10 seconds.

After the debit stage you are flowing an additional 60ml in 20-25 seconds. So you are actually pushing around 3oz of water to achieve the 2oz shot. The extra 1oz is retained in the properly saturated puck. So from an unrestricted group, you should be getting 94ml in 30-35 seconds?

To change the flow on an E61 machine, you would change the gicleur. To achieve the same impact on my Faema, I would put a smaller jet in the group.

With the high flow rate of my current machine, any small defect in the puck is exaggerated. Any small difference in the distribution is exasperated due to the lack of water debit and I am rewarded with a lopsided extraction cone and a blah cup.

Like I said at the top of the thread, I am still learning and trying to take my understanding to the next stage. And get a decent cup at the same time.