Hello Fellow Snobs 
I came across this interesting video today on YouTube in which Luca Bezzera (great grandson of the fella who is known to have made the first espresso using a pressure system) is giving a few blokes bit of a tour around their Bezzera factory. See link to the YouTube video below.
What I found interesting was that he said that the 9bar pressure was meant to be a setpoint for machines with larger pump sizes e.g rotary pumps. He then says that the optimum pressure for small vibratory pumps should be set to around 11bar.
Now if this was just another bloke reviewing an entry level machine, I would have said Mate, don't reinvent the wheel but considering his position I thought I should at least give it a try just out of respect.
So I did and after about three attempts, got my dosing right to maintain around 9.8bar pressure and managed to pull the best shot I have ever poured in six months of owning my BES920 (see stats below and the video in the second link below).
The taste of espresso was definitely more lively and acidic and I instantly noticed the difference. Also ended up with a good looking puck (images in the second link). From now on, this will be my setting for a single shot for my usual beans. I may increase the brew time by another second though.
I'll play around tomorrow to get a tad more pressure and will also experiment with the double basket.
My first thought was to post this in the BES920 owner's thread but I also wanted to hear some experiences from people who own some decent Italian machines with small Vib. pumps (no offence to Breville of course)
Do you set your dosing and other settings to get a decent shot at 9bar or if you have a machine that allows you to brew at specific pressures, have you experimented with higher pressures?
Would you agree with Luca Bezzera that small pumps should be set higher?
The only logic my engineering brain (non hydraulic) can think of is that the pressure gauge typically measures the pressure in the boiler and a small size pump may not be able to maintain the same pressure in the brew head due to some losses in the pipework along the water path but it may be possible to maintain the brew head pressure same as the boiler pressure with a larger pump.
Thoughts?
Stats from my test shot:
Machine: Breville BES920 Dual Boiler
Basket: Single cup 15g Breville stock (non pressurised)
Grinder: Mazzer Mini Electronic Mod A
Beans: Medium roast with good acidity (Brazilian/South American Blend) air roasted on Monday by a local roastery (5 days ago)
Water: Sydney Inner city tap water with Breville filter in the water tank
Shot Size: 14.1g
Grinder Setting: Very slightly finer than my usual
Grind Time: 10.25sec
Tamp Pressure: Approx. 30% more than my usual 9bar brew
Brew Temperature: 93deg
Pre-Infusion: 7sec at 60%
Total Brew Time (inc. Pre-Inf.): 31sec
Pressure: 9.75bar (as shown on the gauge)
Shot Volume: 26.2ml
The OPV operating pressure for my machine is approx 11.5bar.
Referenced YouTube Video:
https://youtu.be/E4y4-E2aL3U
My test shot video and photos:
https://www.evernote.com/shard/s458/...5a2bb05c5a9ed0

I came across this interesting video today on YouTube in which Luca Bezzera (great grandson of the fella who is known to have made the first espresso using a pressure system) is giving a few blokes bit of a tour around their Bezzera factory. See link to the YouTube video below.
What I found interesting was that he said that the 9bar pressure was meant to be a setpoint for machines with larger pump sizes e.g rotary pumps. He then says that the optimum pressure for small vibratory pumps should be set to around 11bar.
Now if this was just another bloke reviewing an entry level machine, I would have said Mate, don't reinvent the wheel but considering his position I thought I should at least give it a try just out of respect.
So I did and after about three attempts, got my dosing right to maintain around 9.8bar pressure and managed to pull the best shot I have ever poured in six months of owning my BES920 (see stats below and the video in the second link below).
The taste of espresso was definitely more lively and acidic and I instantly noticed the difference. Also ended up with a good looking puck (images in the second link). From now on, this will be my setting for a single shot for my usual beans. I may increase the brew time by another second though.
I'll play around tomorrow to get a tad more pressure and will also experiment with the double basket.
My first thought was to post this in the BES920 owner's thread but I also wanted to hear some experiences from people who own some decent Italian machines with small Vib. pumps (no offence to Breville of course)
Do you set your dosing and other settings to get a decent shot at 9bar or if you have a machine that allows you to brew at specific pressures, have you experimented with higher pressures?
Would you agree with Luca Bezzera that small pumps should be set higher?
The only logic my engineering brain (non hydraulic) can think of is that the pressure gauge typically measures the pressure in the boiler and a small size pump may not be able to maintain the same pressure in the brew head due to some losses in the pipework along the water path but it may be possible to maintain the brew head pressure same as the boiler pressure with a larger pump.
Thoughts?
Stats from my test shot:
Machine: Breville BES920 Dual Boiler
Basket: Single cup 15g Breville stock (non pressurised)
Grinder: Mazzer Mini Electronic Mod A
Beans: Medium roast with good acidity (Brazilian/South American Blend) air roasted on Monday by a local roastery (5 days ago)
Water: Sydney Inner city tap water with Breville filter in the water tank
Shot Size: 14.1g
Grinder Setting: Very slightly finer than my usual
Grind Time: 10.25sec
Tamp Pressure: Approx. 30% more than my usual 9bar brew
Brew Temperature: 93deg
Pre-Infusion: 7sec at 60%
Total Brew Time (inc. Pre-Inf.): 31sec
Pressure: 9.75bar (as shown on the gauge)
Shot Volume: 26.2ml
The OPV operating pressure for my machine is approx 11.5bar.
Referenced YouTube Video:
https://youtu.be/E4y4-E2aL3U
My test shot video and photos:
https://www.evernote.com/shard/s458/...5a2bb05c5a9ed0

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