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Thread: Ghetto pressure profiling

  1. #1
    Senior Member Magic_Matt's Avatar
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    Ghetto pressure profiling

    [Edit - title should read "preinfusion" not "pressure profiling"... don't mind me...]

    So, maybe I'm not the first idiot to think of this.

    Here's the drum:

    You have a pump-driven machine with manual (as opposed to volumetric or timed) control.

    To implement basic preinfusion, you cycle the pump on/off briefly one or more times before turning full on for the duration of the shot.

    Bonus points: on a machine with E61 group, you push the lever to the middle position (pump disengaged but solenoid/exhaust valve closed) before the end of the shot, to give declining pressure toward the end of the shot.

    I've experimented with something like: on (2 seconds), off (4), on (2), off (2), on(*) [leave for duration of shot].

    And at the other end; once output hits about 30 g and 25 seconds (from (*), so not including preinfusion), turn off pump then engage solenoid once output hits about 40 g in 30-35 seconds not including preinfusion.

    So, a few questions...
    0. Has anyone else tried this?
    1. Is it likely to cause premature wear or damage to the machine?
    2. Is it a dumb idea for some other reason?
    3. If yes to 2, why?
    4. Should I just buy a lever group machine?
    5. If no to 4, should I just buy a Slayer?

  2. #2
    Senior Member readeral's Avatar
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    0. Only when I've run out of water my "off" is about 10 seconds :P but have toyed with the concept over the past year, never done it deliberately. Maybe next batch of fussy beans I'll give it a go.
    1. I'd doubt it, unless the rapid manual switching of current (which is essentially how the motor/oscillators work anyway right?) would cause damage.
    2. With a rotary, _maybe_ the second pulse would break up the puck? (Heavy emphasis on maybe.. but due to immediately available 9 bar pressure rather than ramping up of a vibe)
    4. Nah, way more for you to explore on that Syncronika but if you do, I'll buy it. (Read: I'll battle Angie over it)
    5. If you can afford a Slayer, I've totally pegged you wrong...
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  3. #3
    Senior Member matth3wh's Avatar
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    Sounds like he may want to buy a Slayer or Lever though :-)

    [for those without e61 plumbed in line pressure] - Have you tried using a dropper to drip a few mls on to the puck first to pre-wet things and then insert in to portafilter and switch on ?
    Last edited by matth3wh; 1st March 2017 at 10:36 PM.
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  4. #4
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    I used to do this on my two E61s (HX and DB) by turning on, waiting until full pressure, moving to middle detente until first drops appeared on the bottom of naked and then turning on again. Worked well for extremely thick and short shots.
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  5. #5
    Senior Member Magic_Matt's Avatar
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    Thanks for the replies

    I've been getting good results with this technique, as per kwantfm it really shines pouring the double ristretto for my morning 3/4 flattie, that tends to be low 'n' slow.

    One of the bbiggest improvements is little to no channeling - used to get 'spurters'- but I also changed my distribution technique so hard to know whether the preinfusion is responsible.

    @readeral have done the empty tank shutoff preinfusion a few times haha - actually it was what gave me the idea! I thought the Synchronika was meant to only go into standby after finishing the shot, but I guess it's one more reason to plumb in.

    Slayer... hmm... well, let's say given how much strife buying smashed avo for brunch can generate it's probably better not stir the possum . The tldr version of the first post is that I'm copying the EM6910 preinfusion, so maybe I should get one of those instead. There's even that mod of adding a light dimmer to the pump power line for genuine pressure profiling...

  6. #6
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    Cycling the pump on and off on my machine would result in the 3 way valve opening to the drip tray mid shot. Not ideal!

    I fitted a needle valve in bypass around the pump (a common method for pump flow control). Much easier.
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  7. #7
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    I thought previously about doing something like this on linea mini but first flip of the lever produced about 1 tbsp of water and next flip produced none so gave up quickly
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  8. #8
    Senior Member Magic_Matt's Avatar
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    Yep; will only work on certain machines (I'm tempted to say E61 but I'm sure there are others).

    I actually need to push the lever slightly past the middle detente ("the easing of hostility or strained relations, especially between countries" ) to engage the pump; slightly past down engages the solenoid. Not sure whether that's normal or not, but it's handy...

  9. #9
    Senior Member readeral's Avatar
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    I had a crack at this today.

    This morning, worked a treat. I normally pull long shots (1:2 ratio) but was able to get a nice rounded extraction at about 1:1.2. This afternoon I had a crack, but I didn't get my ons/offs right, introduced a bit too much water to the puck I think, and it didn't work as well.
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  10. #10
    Senior Member readeral's Avatar
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    Behmor Brazen - $249 - Free Freight
    Obviously, repeatability is an issue with this method, mostly I think as it is making finer movements and muscle memory won't kick in nearly as hard as when using a lever machine. But, I'm willing to keep working at it, cause I think it has some merit.
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