More elaborate reply: Slayer comes from the factory at 2ml/s I believe, pushed through a needle valve with 9 bar pump pressure behind it. What this means is that the machine can continue to push that low flow until the machine hits 9 bar. This is different from line pressure based preinfusion where pressure quits rising when like pressure is reached.
DE1 does have more headspace and that may be why the standard Slayer shot is set to 3ml/s. Really, The DE1 can do about anything flow wise. I use a Slayer profile I made that uses a 1.4ml/s flow since that is the flow a lot of users seem to adjust their Slayer to. I flow 1.4 ml/s flow to 6 bar of pressure, which takes 30-45 seconds depending on dose and coffee. 3 ml/s will half that time so really it depends on how long you want the preinfusion to last. Then you rise to 9 bar and hold or start a pressure decline.
Thank you! I can tell this machine will be a lot of fun to use. I was reading more from Scott Rao's advanced mode for the DE1, and the settings seem limitless.
I can envision my advanced mode profile looking something like this for lighter roasts:
Preinfusion at 1.4 ml/s to 6 bar of pressure (as you have above)
Then rise to 9 bar, hold for 35 seconds or flow exceeds 1.25 ml/sec
then switch to flow mode, hold at 1.25 ml/sec (resulting in pressure decline)
And then of course I could try adding a bloom period after preinfusion...
I get that it all depends on taste, how beans are roasted, etc, but I think I am finally understanding the capabilities of this machine. The more I understand, the less important I think Version 1.3 gets with the manual controls. Would I ever really use them? I suppose if you grind wasn't yet dialed in, and flow was faster than desired, you could manually lower the pressure on the fly to compensate. That might help that particular shot, but I would still increase dose or grind finer next round. Once dialed in, the automatic profile will be far more reliable. When I originally was thinking about Version 1.3, I was hoping it would be more like a tactile paddle similar to the Bianca/LM GS3/Slayer. But with LCDs only, it may simply be a feature that doesn't get used often. We'll see as more details come out.