9 bar or 11 bar – What is the right pump pressure for the espresso machine ??

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Luca Bezzera explains why small machines with vibration pump need 11 bar and the big rotaty pump is fine with 9 bar. Luca Bezzera erklärt, warum Espressomasc…


clint87ua says:

Ich Kaffeemaschine mit einer Pumpe ULKA EP5, die bei 230V arbeitet, aber
das Netzwerk immer 205-215V, Kann mein Gerät nicht, weil es Probleme mit
Strom arbeiten?

Dimitris Daskalakis says:

Wow I’m impressed! That’s Italian and German bro science at it’s best!
9 bar is 9 bar, 10 bar is 10 bar, 11 bar is 11 bar either it comes from a
“professional” or a “toy” pump. But if Illy says 9+ bar then that must be
So to clear things up, the semi professional machines may have a group head
valve before the portafilter which is a resistance valve with a little
spring (maybe set at 2 bar) so if your OPV is set to 11 bar the actual
pressure that lands on your portafilter is 9 bar. But if you have a
solenoid valve like the “little David” has, you don’t need that extra

Razvan Pana says:

Yes, it’s true, I tested my home espresso and coffee from 9 bar is bad
taste, as pressure increases is getting better and better. Thanks for the

Elize Freeman says:

well interesting video, thanks “gis a job”

Dino Rebstock says:

Oh Mann… also muss ich mein EX-Ventil jetzt so einstellen, dass es zw. 10
und 11 bar liegt, gemessen mit einem Siebträgermanometer, wenn ich ne ULKA
habe. Die ist in meiner Isomac Millenium nämlich drin. RIchtig? :-)

ferrei80 says:

I bought the BZ10 machine a week ago, but then the pump started
malfunctioning during extraction, with the brew pressure fluctuating
between 6-9 bars (dose/grind adjustments didn’t help). After I took the
machine back to the authorized dealer, the technician said the pump should
have been factory adjusted to 9 bars. He claimed that the 11 bar setting
caused the pump to prematurely malfunction (it needed replacement). He
adjusted the OPV setting to 9 and replaced the pump.

Who do I believe, and why am I receiving conflicting information from
Bezzera and it’s authorized dealers? I’m not impressed.

poppiesrule says:

What an exciting opportunity to check out the Bezzera factory! I would love
a tour of the facility and an explanation of what all the equipment we saw
in this video is for. I noticed service panels at the back of the bench to
power the different machines and a lot of gauges that can measure pressures
at different points in the machines. I wonder where they check the
pressures and what other equipment they have to calibrate and tune espresso
machines. This is fascinating, good job!

TheEspressoTV says:

I cannot read your link to the differences, but in fact both pumps are
totally different in their pump curve – The operating design point of a
pump lies at the intersection of the pump curve and the pipe curve… At
least I can say that I did engineering for plants for some years. But in
the tasting result there is not so much difference I have to admit.. I
personally prefer the rotary pumps, they are not so noisy. Ciao markus

Rudolf Artner says:

SPITZE!! Danke für diesen augenöffnenden und tollen Beitrag! Ich stelle
meine VBM nämlich seit Jahren nur nach persönlichem Geschmack ein und bin
seit Anfang an bei 10 bis 11 Bar. Übrigens musste ich feststellen das es
auch mit den 7 Gramm Kaffeepulver bei der VBM nicht hinkommt, ich muss
immer ein bissl was nachfassen um das gewünschte Ergebnis zu erhalten. LG

jonr5000 says:

You say over and over that you need more pressure, but you don’t clearly
explain why. I’m going to guess that the problem is that on the smaller
machines, 11 bars at zero flow results in 9 bars when a shot is flowing.
But it would be better to measure and set the pressure with flow instead of
measuring at zero flow and then trying to correct the measurement by adding
two bars.

TheEspressoTV says:

well, this is very basic in mechanical engineering of fluid dynamics for me
to explain, but fluid dynamics does not understand everyone. It is Q=v * A.
So I try to explain it with cars and not with math. A V8 4200ccm cylinder
motor needs less rpm than a 2 cylinder 2CV motor with 600ccm to each the
same speed. Similar it is with pumps, the rotary pum has much much more
capacity, so it needs less pressure… Ciao Markus

TheEspressoTV says:

No,you do not understand the function of a vibration pump. It is calibrated
at 11 bar, but the pressure on the brew unit depends on the amount of
grounded coffee and the grinding degree and the tamping pressure. Good
extractions are acchieved with vibrationpumps between 10 and 11 bar
extraction pressure at the group. You can check it at the manometer of the
brew ghroup, but you see it in the result of the outflow and in the
creaminess of the espresso.

dimogrec says:

very interesting thanks! by the way I love the “decoration” of bezzera
factory ( 3:31 and 5:24 ) 🙂

m4tth3wh says:

So the Bezzera domestic espresso machines with ulka pumps set at 11 bar.
Does this equate to approx 9 bar at brew head during extraction?

335Mat says:

Interesting explanation and demonstration. Good job. Thank you for this

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