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.

"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.

cannonfodder wrote: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?

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.

cannonfodder wrote: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.

cannonfodder wrote: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.

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.

cannonfodder wrote: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.

cannonfodder wrote: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?

AndyS wrote: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?

cannonfodder wrote: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....