E61 pre-infusion chamber volume and pressure?

Need help with equipment usage or want to share your latest discovery?
boren

#1: Post by boren »

E61 groupheads use a pre-infusion chamber, but I can't find any information about the actual pre-infusion profile, i.e. the amount of water that passes to the puck for this purpose, how long it takes, and what's the pressure profile. Can anyone share this info?

Pressino

#2: Post by Pressino »

Depends on the spring constant (how "strong" the chamber spring is).

boren (original poster)

#3: Post by boren (original poster) »

Is there some default/recommended spring strength? Do you know what Faema is using?

JRising
Team HB

#4: Post by JRising »

It varies from machine to machine. Some are soft enough to fill the pre-infusion chamber at less than 2.5 Bar (that's what my water-line regulator is set to). You could simply remove your drain valve and see what yours is set to by adjusting your pressure regulator(Assumption made that there isn't a 2-way solenid valve preventing your line from pressurizing the machine when off, pumps can be unplugged if needed). Or one can assume approximately 2.25 to 4.5 Bar.

Pressino

#5: Post by Pressino »

One way to tell how your machine's infusion chamber spring is working would be to install a pressure gauge in the nose port of your e61...just like the ones used with those now popular e61 flow control gadgets. Prepare your coffee puck as usual and then just watch how the pressure changes over time during the extraction. As JRising says, you will be able to see the pressure at which the spring opens exposing the puck to full pump pressure.

If you know the volume of the infusion chamber and plot the pressure gauge reading over time, you can figure out the hydrodynamic "pre-infusion" pressure profile for your particular e61/machine pump combination.

BTW, here's an excellent brief explanation of e61 "pre-infusion:" http://coffeetime.wikidot.com/e61-pre-infusion

I put "pre-infusion" in quotation marks because I think it is a misleading term. It is just part of the whole coffee infusion which begins when the brew lever turns on the pump and runs until extraction is completed. :wink:

User avatar
Randy G.

#6: Post by Randy G. »

IF you Download the VBM Double Domobar owners manual and read through pages 5-7 it explains haw the manual E-61 group operates. As other have said, the strength of the infusion spring dictates the force at which the infusion chamber opens and thus the length of time that pre-infusion takes place. It was a very interesting design that allows the puck to take in some water before pressure ramps and avoids the "water hammer" that would otherwise hit the puck. Does it work? The patent was filed 62 years ago and the group is still in production. That seems to be evidence enough.
www.EspressoMyEspresso.com
* 22nd Anniversary 2000-2022 *

Amberale

#7: Post by Amberale »

To address your real concern, Lelit fitted the Bianca with a heavier spring which prevents this E61 feature.
This is because the Bianca is designed to be used with the FCD.
Some folks have used their old springs when retro fitting FCDs to their machines, I still don't know why.
:?

Pressino

#8: Post by Pressino »

Amberale wrote:To address your real concern, Lelit fitted the Bianca with a heavier spring which prevents this E61 feature.
This is because the Bianca is designed to be used with the FCD.
Some folks have used their old springs when retro fitting FCDs to their machines, I still don't know why.
:?
Because, like me, they have found that using the original spring allows both traditional e61 early infusion and the ability to adjust flow/pressure during the later extraction.

boren (original poster)

#9: Post by boren (original poster) »

If I understand correctly it seems that in terms of the first seconds of pre-infusion, E61 resembles the recent best practice profile for Decent machines - start with high flow to quickly fill the grouphead, followed by ramp up to 3~4 bars, pause using this pressure for about 8 seconds and then increase to 9 bars for the main extraction. One key difference is with E61 there's no blooming stage (pause) between those two pressure, i.e. the part that's marked with a red rectangle here:



This however is something that the Bianca can be programmed to mimic. What I'm less clear about is whether this step (step #2, "Low pressure preinfusion") should use the Bianca's low flow mode or regular flow. Low flow would take longer to saturate the puck, which I'm not sure is beneficial as it would mean the upper part would extract differently than the lower part.

User avatar
Jake_G
Team HB

#10: Post by Jake_G »

Actually, there is a pause.

When the PI spring is overcome and the valve is cracked open, the pressure will remain at the cracking pressure of the PI valve until the chamber is filled.

Pressure will not rise until the chamber is filled, and then it will ramp up to the main brew pressure.
LMWDP #704