I think Jake hit the nail on the head…there are various different groups and it really does depend on what they are attached to. Sure the e61 was designed in 1961…that doesn’t make it necessarily bad because of it’s age…look at the LSM spring lever group.
In the olden days, these groups were put on very different back ends…pipe sizes, thermosyphon restrictors, dual boilers and PIDs were not even thought of back then. These groups used sheer mass to make them work in the absence of all this stuff.
there are different types of “saturated groups”
- attached with a big duct (GS3 style)
- part of the boiler (Dalla Corte Style)
- ring group bolted to bottom of boiler (more conduction that saturated (although I have heard them referred to as saturated
- ring group (variants with heater cartridges)
- LSM Lever group with heater cartridges ala Evo or Nurri
Notice I have not mentioned the Micra group as it’s own category because it’s very, very, similar to the ring group concept, with a short water path to the group.
For me a true saturated group would be one where the entire group is double chambered, including where the portafilter locks in and is in effect a boiler as well….no bolt ons…so everywhere the portafilter and the water above it touches, is touching a wall, behind which is boiler water….so we don’t quite have those….although Dalla Corte comes very close as does LSM with heater cartridges (once it’s filled of course!).
The LSM has something the Dallacorte and others don’t a counter current flow when the group is filled and the ingress of close to brew temperature water (if desired). The counter current flow ensures an “stabilising” layer of water that gives up enough heat to even the temperature dynamic across a wide vertical area of the group. Otherwise a “relatively” significant temperature gradient exists. The group has now become almost a saturated group, being actively heated with 220W of power and water perhaps only needing a 1C touch up…no more cold water entering the system (as in a boiler) and no artificial disturbances of temperature sensors.
So modern technology and thinking coupled with a 1950 group….“possibly” gives the best temperature stability potential of all?
That said, an espresso machine and satisfaction is more than just about temperature stability…important though that might be.