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Where does LR digital preinfusion fit into process of dialing in a bean?

My typical process of dialing in a bean goes something like this:

1. Adjust grind to achieve a 1:2 (dose : yield) ratio in ~30 sec.
2. Pull another shot, stopping short for a 1:1.5 ratio.
3. Pull another shot, stopping long for a 1:2.5 ratio.
4. Taste each of the three shots, and pick the ratio I prefer based on taste.
5. Keep selected ratio constant, adjust grind (finer or coarser) to get desired taste.

The above process assumes a static preinfusion pressure.

Where does the digital preinfusion capability of the LR fit? Do I arbitrarily pick a preinfusion pressure to start with? If so, what pressure? Do I adjust preinfusion pressure after step 5?

How do I know if my preinfusion pressure is too high? Too low?

I appreciate the help as I'm new to the LR. Previous experience has been E61 machines where my I had no ability to control preinfusion pressure.


  • hi lee

    i tend to take a simpler approach, using the machine to make life easy as i have designed it that way

    a dark roast likes a shorter shot, as they extract more readily, and the opposite for a light roast

    my machines take care of this for you as a change in pre-infusion pressure moves all the parameters in the correct direction

    so use a constant dose to get started, typically 18g in our 18-20g IMS basket, and just vary the pre-infusion pressure

    the LR comes set to 3 bar at the puck out of the box (ensure the offset is -1.0 bar not -1.4), and this isnt a bad place to start

    if you have a dark roast you are going to be dialling the pre-infusion right back to boiler pressures that we had on the L1(2012-16), eg 1.3 bar and the lever will grab much higher and the shot will be much short to prevent over extraction and it all works in harmony to get you an optimal extraction

    you might even drop down to 1.0 bar pre-infusion

    i would define a dark roast as one having oil on the surface of the bean - bear in mind that a relatively dark roast will not have much more than pin pricks of oil on the surface of the bean when first roasted; the oil comes to the surface with the passing of time

    the lighter the roast the more pre infusion pressure you give it

    this automatically gives you a higher brew temperature at all points on the curve, brings much needed body to light roasts, and increases the shot volume (i.e. it automatically extends the brew ratio for you - you dont have to worry about any of that fluffing around)

    does it taste burnt or sour (a slightly queasy taste), or sweet?

    if it is sweet you are bang on; dont change anything

    more likely you will be under or over on the first shot though, so if it is sour go up 1 bar and try again using the same dose, grind, tamp, etc

    if it has burnt notes then drop 1 bar and try again

    if a movement of 1 bar takes you too far, ie. a sour roast now exhibits burnt notes or vice verse, split the difference, i.e. drop back 0.5 bar back towards the pressure value that you started with

    keep splitting the difference in this way until you get it just the way you like it

    be aware that the taste of a coffee shifts as it ages, with the CO2 gassing off in particular in the early days post roast really moving the taste around, so you can expect to have to tweak the pre-infusion pressure every day if you insist on drinking coffee that is too fresh

    let me know how you get on - great question!

  • Hi Reiss,

    Thank you very much for your helpful reply. I discovered that my machine's offset was -1.7, so I reset it to -1.0 as you directed.

    I'm using a med-light roast (Goshen Coffee's Bona Fide espresso blend) and kept a constant dose, and started with a 3.5 bar preinfusion pressure. I then brewed shots at various pressures, and here's what I found:

    2.5 bar = more sour
    3.5 bar = sour
    4.5 bar = less sour
    5.5 bar = sweet; slight hint of sourness

    I ran into some pump-related issues at 4.5 bar and higher, which I posted about under the LR help forum, so I wasn't able to establish a relationship between preinfusion pressure and preinfusion time.

    I'm still undecided about where to insert preinfusion adjustment into my dialing in process (before or after determining brew ratio), so I've got more experimenting to do.
  • hi lee

    just getting my daughter off to school and will reply to both your posts more fully in a couple of hours, but your data above suggests to me that your coffee remains 'sour' or 'slightly sour' at such high pre-infusion pressures because either your puck prep has scope for improvement, or you have some silicone grease in your shower screen, or both; but i am almost certain you have some channelling going on and for this reason the shot will remain sour regardless of the pre-infusion setting

    can you post a short clip of an extraction and another with the portafilter removed from the group and a short flush of the group so i can observe the water fall pattern through the shower screen for any signs of jetting

    more later

  • Reiss,

    Thanks for your help. Yes, the shot still tastes sour. Please excuse my terrible videography.

    I seem to be unable to figure out how to post a video. Here are the links:

  • hi lee

    what you have posted looks pretty good - how many days post roast is the coffee?

    to put it in perspective i only go above 4.5 bar for very light roasts, hence my surprise

    kind regards

  • please confirm:

    1. that the machine has been on for one hour

    2. that you have removed the red plastic shipping tag from the anti-vac valve on the boiler, as shown in the image below

  • Reiss,

    The beans are 11 days post-roast. The machine was on for 2 hours prior to pulling the shot, and I did remove the red tag pictured.
  • that all seems pretty reasonable lee

    i recommend that you drop the shower screen and give it a clean to remove any excessive silicone grease that has made its way down

    you will need to use a citrus solvent or acetone or other favourite nasty of your choice. be sure to rinse thoroughly under a running cold tap afterwards

    espresso machine detergent does not dissolve silicone grease and neither do descaling acids

    whilst i think of it, what is the pump delay set to on your pre-infusion module? 1000mS?

    kind regards

  • one more thing; please confirm that the boiler pressure does not exceed 1.0 bar when the heating element (red light) turns off

    kind regards

  • I'll pull the shower screen and use citrus solvent to clean it tonight -- gotta get the kids to a baseball game now.

    I set the pump delay to 500ms in an effort to fault trace. It exhibits the same behavior at 1000ms and 500ms. If I'm splitting hairs, the heating element turns off at 1.03 bar -- the boiler pressure does not exceed 1.04 bar, and the heating element turns back on at 0.85 bar. I haven't adjusted the boiler pressure at all.
  • hi lee

    no issues there then

    thank you for confirming that you haven't altered the boiler pressure

    you might want to try dropping the delay to 100mS for higher pre-infusion pressures

    kind regards

  • Reiss Gunson post=16093 wrote:

    to put it in perspective i only go above 4.5 bar for very light roasts

    Oh no, I’m at 5.5 right now with one of my roasts! Maybe I should bring it down tomorrow
  • maybe you have a very light roast? :dry:
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