Thanks, Doug. No worries about my cutting into the case. If I leave the screws out of the cup warmer I can lift it off for immediate access to the PSTAT dial.
I've done some measurements today. Here's my "Scace Lite." My new, larger drill wouldn't hold a very small bit so I punched a hole in the side of the basket with a nail and filed off the sharp edge.
Added: As I've thought about these temperature profiles it occurred to me that they show a trend that is very different than with home lever machines. In Tekomino's Cremina temperature studies the temperature rises and then begins a very slight decline during the pull. Watching the thermometers on my La Pavoni levers the temperature steadily rises during the shot. With my commercial lever the temperature declines after the preinfusion and drops in a fairly smooth, steep curve to make a far more nuanced espresso.
With apologies to the many disciplined engineers on this site, here's my first test run. Let's just say I'm discovering where the saddle is and trying not to fall off the horse at this point. I rigged my thermocouple to Artisan and used the magnification function to get some tracings. The test wasn't carefully controlled but it did show me some beginning temperatures at pre-infusion and that temperature during a pull has a fairly stable decline. I dosed 19 gm of an underdeveloped roast into the double basket, did approximately 15 second pre-infusion, then ran shots that often went well over one minute. This didn't stall the lever. As noted earlier I haven't fine-tuned shots in this machine. I could re-do some trace captures and perhaps fine-tune the grind. But let's see whether I have the information I need, which is whether a 0.55 bar deadband in a PSTAT on this machine is too wide a swing for my tastes.
My initial take with this rough testing is that the initial temperature varies by as much as 19 degrees over this range. The lowest initial temp was 183, the highest was 202. Even throwing out the 0.9 bar initial reading of 202, where the portafilter was locked in a bit longer at the start, and going with the 1.0 bar reading of 196, I get a 13 degree difference. What also stands out is a large and fairly steady decline in temperature, about 20 to 30 degrees in the normal course of a well-tuned shot of let's say 30 to 40 seconds. This tells me that this Prestina both softens the shot with lower temperature and reveals more layers of flavor that are shaded one into the next through a large temperature swing. The initial flavor accent of boiler temperature water settles steadily to much cooler temperature where the group is idling. This is in addition to a steadily declining pressure profile. The large difference in initial temperature that then declined more steeply was enough to change the taste on this failed roast from very sour at cooler pulls to slighly sour at hotter ones. I want a narrower deadband on my PSTAT to set the initial temperature where I like it, so I think I'll put the Sirai in there.
Here's the tracing for 0.45 bar. Initial temp is about 183 and it declines to about 155 after a minute.
0.6 bar (the Amprobe data logger had shut itself off and I had to restart, so missed the starting number). This one isn't that useful and I would have to redo it:
0.7 bar. Initial temp is about 185 and it declines to 155 after one minute:
0.8 bar. Initial temp is about 192 and goes to 158 after a minute:
1.0 bar. Initial temp is 196 and goes to 156 after a minute:
I didn't capture the tracing for the 0.9 bar pull but did record the numbers in Artisan, as follows, which tells me it started at 202F and declined rapidly once I released the pre-infusion. That must be where it moved from 187.3 to 182.1. It eventually declined to 160.6 when I turned off Artisan.
202.0, 200.9, 198.8, 198.7, 197.4, 193.5, 191.6, 188.9, 187.3, 182.1, 181.9, 179.8, 179.3, 177.8, 177.7, 176.5, 175.3, 175.1, 173.2, 173.0, 172.8, 172.5, 172.1, 172.0, 171.6, 170.7, 170.5, 170.3, 169.4, 169.0, 167.6, 167.5, 167.3, 167.2, 167.0, 167.1, 167.0, 166.9, 166.8, 166.8, 166.6, 166.4, 165.4, 165.2, 164.0, 162.8, 161.2, 160.9, 160.6
Added: Discussion of this temperature profile yielding flavor differences seems worth continuing on my Conti Prestina Owner Experience thread.
There's an old thread where I've added this observation. It's here:
The temperature profile of a commercial lever group