MediumRoastSteam ok. So why was the chamber there in the first place if it’s not necessary?
Well, the issue was one of marketing as usual…in the olden days features were promoted as points of difference….no one really cared whether they made a true difference or not. It’s happening again today with the latest crop of influencers, they will shill a difference with almost zero technical/scientific knowledge. They then dance around with the espresso in yumtown depending on which mod they are shilling today.
In the past not one, not a single person reviewing mentioned the shot stopping when the water tank was empty, or the (occasional) autofill of a steam boiler if you steamed and brewed at the same time spoiling the espresso shot. No one seemed to care. Apart from me that is and it took me a few years to convince manufacturers to put proper “Last shot protection” in, to fix both these problems. I invented it, I cared about it, because it was what people needed, they didn’t know they did of course. Now a partial implementation is almost de rigeur in espresso machines (sadly the autofill lockout is often missed out). On machines that don’t do any of this, reviewers still don’t mention it as a negative…to “force” the manufacturers to implement it.
So we come back to the preinfusion chamber…here’s some facts for you:
- The preinfusion chamber fills so fast with the hi flow of a rotary pump, that it’s an almost unnoticeable 4 or 5 bar pause in the pressure rise.
- The puck is still hit with 4 or 5 bar pretty rapidly
- It does add a small amount of extra thermal mass due to the water it contains (but the effect is negligble, as I tested this 9 years ago
- The slow rise of a vibration pump is actually way better than a rotary, if it wasn’t for the noise we would all be using vibration pumps
- Vibration pumps mostly sound horrible (except Lelits quiet pump tech, which is more bearable)
- Rotary pumps are great marketing, the preinfusion chamber is also great marketing.