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The Bosco group sure is still connected to the boiler but it is with a longer narrower neck in between (thus lesser heat transfer to the group). My previous understanding (from others' comments) was the water in the reservoir will be slightly cooler than the boiler water - is that correct?

JohnB. wrote:The group will certainly be hot before this time but you won't get the same brew/shot water temps without flushing more water through the group if you pull shots prior to the group reaching max idle temp.

We're on the same page I wasn't talking about just hot group (which happens earlier) but actually reaching its max idle temp (via measuring the group temp). Being a dipper means, regardless of how long you have it on (after reaching equilibrium), the idle temp will always be a touch lower than operational equilabrium temp - a short flush is needed to wake it up from idle/cold.

I am curious what boiler pressure/temperature setting produces good shots.

I've kind of been keeping my eye on the various boiler temp settings for dipper-group, boiler-fed single group levers. My DIY dipper works best around 240-45 degrees F but with different group-head temperature settings I can make good shots with boiler temps at 240-260 degrees. It seems that Conti Prestinas give good shots with a boiler temperature around 258 degrees and the Quick Mill Achille PID just posted had a PID setting of 244 degrees.

My current settings are 241 boiler temp and 221 for the group head. The actual group head temp (measured at the base of the snout) idles around 197. When I'm pulling shots I start each shot when the group head temp measures 202. It takes around 3 minutes to settle down between shots.

That pressure gives temps right in the same range but the specifics depend on your altitude.

That works out to be 254-255 degrees F.

Question for the owners of dipper tube lever machines. If Bosco implemented the use of said custom reservoir at the connection of the boiler with the main frame, then it makes you wonder how the other dipper tube lever machine deal with temperature management. How much of "temperature management" is involved with your machines?

For example, in situations like Dan's "Cars n Coffee" YouTube video (pulling shot after shot after shot), is there any overheating and therefore burnt espresso taste of subsequent shots? And if pulling shots at a "normal rate", e.g., every 3-4 minutes or so, do you need to flush before pulling a shot? Will temperature stabilize in any of those situations?

Or, will water passing through the puck will thermally stabilize at any of those situations?

By the way, the Pro 800 looks like a really nice machine.

Javier wrote:Question for the owners of dipper tube lever machines.

How much of "temperature management" is involved with your machines?

Or, will water passing through the puck will thermally stabilize at any of those situations?

There is a temperature gradient from the boiler, through the boiler connection, through the gasket, to the group's piston/cylinder, then finally to the puck. If you look at dipper machines you'll see a wide variety of different arrangements and each one will make for a different temperature delta between the boiler and the group.

They all can work but I think the difference is 1) what is the group's idle temperature given the boiler temperature/pressure set point, 2) how big is the temperature delta at steady state, and 3) how fast does heat flow from the boiler to the group head. These factors impact the time between shots that a lever group can pull without the temperature of subsequent shots climbing. The lower the temperature of the boiler the less heat that us pushed into the group head when a shot is pulled. The slower that heat flows from the boiler to the group head the less time it takes for the group to cool from the shot temperature to the shot starting temperature.

Now, I'll describe my temperature management routine. My group idles at 197-199 and the starting group temperature I use is 199-202. I use the lower of the range for coffees that don't have sour notes and I'll go up the the higher end of the range to reduce sourness (I'm very sensitive to sour). To ensure all three double shots I typically pull are the same temperature as I do one or two "fake shots" by pulling the shot(s) using a blind portafilter with a small hole that flows in about 15 seconds. I also grind, prep, and tamp between lever pulls to give the group time to cool down.

So, here's the simple version of the routine. Basically, I flush to bring the group head up to temp, I then prepare each basket between shots, and I start each shot when the group hits the starting temperature. It works out to doing a shot every 3 minutes or so.

Since I weigh my beans and weigh my shot detailed process is a little long-winded. Here are the detailed steps I do:

1. pull fake shot 1
2. pull out espresso gear (portafilter, scale, baskets, etc.)
3. pull fake shot 2
4. weigh, grind, WDT, and tamp basket for first shot
5. when group head temp hits starting temperature pull shot 1
6. weigh beans then stop shot at desired weight
7. grind, WDT, and tamp basket for next shot
8. remove portafilter, dump puck, rinse, then remove and dry basket
9. when group head temp hits starting temperature (typically 2 1/2 - 3 minutes) lock portafilter then pull shot 2
10. weigh beans then stop shot at desired weight
11. grind, WDT, and tamp basket for next shot
12. remove portafilter, dump puck, rinse, then remove and dry basket
13. when group head temp hits starting temperature (typically 2 1/2 - 3 minutes) lock portafilter then pull shot 3
14. stop shot at desired weight
15. remove portafilter, dump puck, rinse, then remove and dry basket
16. do short blind flush to clean group
17. hit manual fill switch to refill boiler to top water level

It seems more hassle than it turns out to be in practice. However, I do know that I'm a bit picky about the process.