TrlstanC wrote:There's so many changes happening at once, that it's tough to tell what matters and what doesn't. Lower pressure shots are something that people have been experimenting with for a long time, and some people definitely prefer with some coffees. But the idea that the heated grinds in the Mythos is key doesn't seem like a reasonable assumption to me, for a number of reasons.

* I believe the idea of the heated mythos was to replicate a cafe grinder under heavy use? The idea being that a grinder under heavy use heats up, that changes the burr geometry and requires an adjustment. With the Mythos it heats up to a set temp to allow the coffee to be dialed in, and maintains the same temp even under heavy use by just reducing active heating as use creates more passive heating. If heating the grounds was key, this would imply that shots pulled when a cafe was busy (and the grinders had been adjusted), would be noticeably better? Basically, I don't think the Mythos was designed to heat the grinds to an unusual level.

* The mythos keeps the burrs at 50c, but how efficiently is that transfered to the grounds, and how well do the grounds hold heat? I'd also assume that the exact temp of the portafilter and basket would matter (since they hold and transfer heat better than grounds), and the time between grinding and extraction would seem to be important too. Even how long the tamper (basically a giant metal heat sink) is in contact with the grounds would matter? I didn't see any data where the temp of the grounds was measured?

* Assuming the grounds are at 50c when the shot starts (which seems like a big assumption, but let's start there), that would be a tiny change in the overall heat of the system given that there's much more water and it has a much higher specific heat. Quick back of the envelope math suggests that a 1-2c change in water temp would be the most that it would take to equalize the difference. This is about the range suggested, but that's also about the range that I'd expect to see between different cafes or between different coffees.

OldmatefromOZ wrote:Hi there,


Which brings me to my point of concern for your machine and I would urge you to check / keep an eye on.
I originally had it set at 6 bar with the plastic OPV screwed in just enough not to pop out.

I was pulling shots with the covers off and it started to drip quite a lot. Much finer grind, preinfusion OFF, 19g dose / 20g VST
38 - 40g out in 40sec. I started to do some backflushing to simulate cleaning and it leaked even more.

So I turned the machine off and released pressure via steam wand, unscrewed the OPV and wrapped the thread with some high temp / pressure teflon tape. After some testing I found its most secure fitting resulted at 7 bar on the gauge. Of course slight difference in machine manufacture = YMMV. Just thought I would put it out there.

John49 wrote:There is an other way to run your BDB at 5-6 bar, adjust your preinfusion settings.
I have been running mine at 70% preinfusion power and setting the time for 60 seconds, shot generally run for 40 seconds.

brianl wrote:I went down to 6 on my machine but got pretty watery and useless results. back up to 7 and it seems to work better. This is with both the on board gauge and one attached to the portafilter (although mine doesn't have a needle valve for flow).