another_jim wrote:Elektra machines perform better than expected, and Silvias worse, if one bases expectations on repeatable and precise temperature and pressure profiles. My guess is that this has something to do with the water path and water quantity.
The Elektra's brew path is straight down, and the dispersion is incredibly over-engineered and even. The space above the puck is tiny, so the amount of water involved in the brewing process is minimized (i.e. a higher proportion ends in the cup and a smaller one in the drip tray). This is reminscent of lever machines, where very little water is wasted (it is drawn into the piston, then pushed into the puck and cup), and the path is straight down. Lever machines are not crema champions, but they are known for taste clarity, despite their crappy temperature control.
The Silvia's brew path is basically horizontal, and the dispersion block is a joke. The entire twelve ounces of water in the boiler is implicated in the brew process, and the amount in the drip tray is fairly hefty.
This is very interesting, because it suggests that design features we normally do not consider may be significant for the best espresso.
I don't think Silvia's dispersion setup is as bad as you say, though. With flow restriction (ie, retrofitted gicleur), her shower screen can deliver an even, gentle rain. It is easily as soft and as uniform as that issuing from the new Speedster. (Please note, I'm talking about a modified Silvia flow rate but with the stock dispersion block and screen).
I also don't understand what you mean by "the entire twelve ounces of water in the boiler is implicated in the brew process." My flowmeter measures about 42 ml water used for a typical Silvia double shot. It works out like this:
Inputs:
42 g water
14 g dry coffee56 g total
Outputs:
18 g espresso
27 g spent puck45 g total
Due to conservation of matter in Newtonian physics

the input must match the output. 56g-45g=9g, which must be the amount of water lost into the drip tray. Is that so bad, 9g lost out of 42g? I plead ignorance, but the 42g of water used to brew a double shot is less than 1.5 oz, a small fraction of the boiler capacity.
I believe Dan has stated that the Elektra machines ramp up to pressure (and therefore, flow) very quickly. Perhaps this is the design decision that necessitates an "overengineered" dispersion system, in order not to disturb the puck.
Is a quick pressure rampup better at delivering flavors, IF one can maintain the puck's integrity? I do not know.
One thing that has always bothered me about my Silvia is the slow
temperature rampup. It takes ~12 seconds to come up to temperature. That's more or less half the shot. This temperature rampup parameter is something that's generally been ignored in all the hoopla about temperature stability. Schomer, the King of Temperature Stability, pretty much ignores the first few seconds. And IIRC, the WBC folks made a decision to ignore the first seconds because they claim their measuring instrument isn't fast enough.
But as you know, Mr. Teahan suggests an unusually hot first few seconds may be useful in bringing the puck up to brew temperature.
I'm just blabbering on here, but is it possible that some of the shortcomings you find in Silvia are due to her temperature profile, not the brew water path?