My long and rambling path to preinfusion/pressure profiling - Page 37

October 21st, 2018, 1:26 pm

My sense is that the Bianca makes slower shots than a tradtional E61 even with flow rates adjusted. To get the 8 to 10 second to first drops dwell time, the paddle needs to be nearly full open, at least on mine. At this postion, the pressure ramp starts earlier and goes more slowly than I remember when using PF gauges on an E61. My guess is that the Bianca has a smaller cavity to fill with water than a traditional E61. In any case, flow measures from the Bianca may not be equivalent to using a needle valve at the pump head, prior to the boiler and group.

#362: Post by **ira** » October 21st, 2018, 1:29 pm

another_jim wrote:My guess is that the Bianca has a smaller cavity to fill with water than a traditional E61.

Wouldn't that require a larger cavity?

Ira

October 21st, 2018, 3:38 pm

Smaller cavity, even smaller restrictor. Lelit has not been very forthcoming with a cross-section or blow up view of their group for the review; so I'm only guessing based on the way it works.

My point is that they've put a lot of work in creating a group where the paddle movement, the pressure at the group, and flow can be coupled very closely (if one avoids large jerky movements). This is unprecedented; neither the GS3, Strada, or Slayer controls, nor even levers (at least with my triceps) are this smooth acting. So I don't think this is a basic needle valve (which are typically a lot stiffer and require more turns), and it may take up more room than one. It feels more like the valve on a very high end faucet.

October 21st, 2018, 6:02 pm

another_jim wrote:Smaller cavity, even smaller restrictor. Lelit has not been very forthcoming with a cross-section or blow up view of their group for the review; so I'm only guessing based on the way it works.

My point is that they've put a lot of work in creating a group where the paddle movement, the pressure at the group, and flow can be coupled very closely (if one avoids large jerky movements). This is unprecedented; neither the GS3, Strada, or Slayer controls, nor even levers (at least with my triceps) are this smooth acting. So I don't think this is a basic needle valve (which are typically a lot stiffer and require more turns), and it may take up more room than one. It feels more like the valve on a very high end faucet.

What makes you think this is different from a "basic needle valve"? My valve modulates from zero flow to 250g in 30 seconds in around 250 degrees of rotation. Were I limited to the 200 degrees of paddle movement that Bianca has, I think I would be spot on for flow rate, although my larger rotary pump for the 2 group keeps the pressure pegged against the bypass even at 500g in 30 seconds. I'm not using anything special, I just spent my time and sized it correctly for my target flow rates and range of valve movement.

Graham J wrote: So, I pulled three shots with two different beans, to your fixed 45g/30secs water flow spec.

Thank you so very much for doing this.

I made a terrible assumption in asking this of you.

This assumption was that since you had a Bianca, you were doing low flow rate preinfusion and grinding fine enough to generate 9 bar of back pressure at this flow rate. Since your tests only hit 1 or 2 bar, it's obvious this is not the case.

However, in doing your tests, it is pretty obvious to me that I must not be grinding fine enough to develop sufficient pressure at this rate, either. The only reason my shots resemble espresso is because the flow rate is so restricted. I'm warming up the machine now and am going to try a shot with a Turkish grind and see what comes of it. I assumed that since my shots weren't gushing after the drops formed that everything was ok with respect to brew pressure, but my crema has been a bit thin since getting the valve in place and I think your examples just told me why. I've also been letting my shots run all the way to hit my target brew ratio.

Thanks again. I'll add a video of my shot for posterity.

**Edit
17g of Turkish grind in the filter basket:

I'm pretty sure I could fit 34g in there at this grind!

I don't have the heart to post the 3 minute video of pulling the shot I just drank. The puck grew far enough that it stuck to the shower screen. I was unimpressed by the appearance of the shot, and got to work cleaning up the mess.

Then I tasted it. I nearly spit it out because of shock, but thank God I didn't because it was exquisite, but unlike anything I've ever tasted. Juicy beyond description. Maybe like a sweet apple cider vinegar but not at all harsh. Same coffee as yesterday. Red grapefruit. Yeah. Like a ruby red squirt. Not a God shot on account of texture and body, but that was the most intense shot I've ever pulled. And in no way was that a bad thing.

**Edit #2**
Loosened the grind up a bit more. Realizing without my group pressure gauge, I'm lost... pity.

Shot was just shy of 2 minutes. I've no idea whether the pressure was 9 bar falling to 6 or only 2 bar at peak. I suspect since the shot was longer than the 58s shots I pulled when I first installed the valve that the pressure is higher, but again, I'm just guessing. I'll pull the group first chance I get so I can get my pressure and temperature fittings installed. This shot was good, but nearly as intense as the 3 minute shot. It honestly tastes more like my shorter shots, so I don't think I would be able to justify the longer shot time, but this is all in the name of science (or something...), right?

Cheers!

- Jake

October 21st, 2018, 8:56 pm

Jake_G wrote:What makes you think this is different from a "basic needle valve"? My valve modulates from zero flow to 250g in 30 seconds in around 250 degrees of rotation. Were I limited to the 200 degrees of paddle movement that Bianca has, I think I would be spot on for flow rate, although my larger rotary pump for the 2 group keeps the pressure pegged against the bypass even at 500g in 30 seconds. I'm not using anything special, I just spent my time and sized it correctly for my target flow rates and range of valve movement.

I guess I'm not familiar with the selection. The ones I tried required lots of turns.

#366: Post by **Graham J** » October 22nd, 2018, 4:44 pm

another_jim wrote:My sense is that the Bianca makes slower shots than a tradtional E61 even with flow rates adjusted. To get the 8 to 10 second to first drops dwell time, the paddle needs to be nearly full open, at least on mine. At this postion, the pressure ramp starts earlier and goes more slowly than I remember when using PF gauges on an E61. My guess is that the Bianca has a smaller cavity to fill with water than a traditional E61.

Thats correct! If you look at my recent 45g/30sec Bianca shots for Jake_G, the cavity is 8-10ml - that assumes the dry puck fills 1:1 by weight, with water.
Being an old gas turbine engineer, I pulled out the verniers and measured a few things, to check - the E61 shower head protrudes down into the portafilter to just on the ridgeline in the 23g filter, when its loaded into the head.Very tight clearance and it is easy to push fit the filter basket onto the shower screen cap..... This means that a a 20+g medium espresso grind will be touching the shower head screen when the portafilter is loaded. Maybe 1-2ml annular space there.
The only other space for water between the screen and the water distribution screw head is a thin annulus that is formed by the inner edge of the portafilter seating seal and the shower screen cup and less than 1mm screen to distribution screw space. Careful design has taken place to minimise the "dead water" head space.

October 22nd, 2018, 4:59 pm

Actually, I wasn't thinking about differences in the puck head space, although Lelit's showerscreen is different from the usual one. I was thinking the needle valve in the Bianca might take up more of the available volume in the vertical part of the group above the levetta cam, so that there is less volume for the water to fill after it wets the puck but before it rises in pressure.

#368: Post by **Graham J** » October 22nd, 2018, 5:02 pm

Jake_G wrote:I made a terrible assumption in asking this of you.
This assumption was that since you had a Bianca, you were doing low flow rate preinfusion and grinding fine enough to generate 9 bar of back pressure at this flow rate. Since your tests only hit 1 or 2 bar, it's obvious this is not the case.

It's fine, I like doing this stuff, even if I do end up with some slurry! As you say, an extraordinary taste experience, except mine was the taste from the top part of the puck, not the full depth. - I never would have tried this shot on my own.
Here's why these grinds can develop into a longer, full pressure shot - several of the Bianca shot profiles developed by Lelit and also by DaveC, start with a 2-3 second paddle right, followed by a swing left to around 40g/30secs position. This short full flow start fills the tiny head space and pressurises the puck away from the shower screen, which it will have been touching when loaded.
Once pressure develops to 2 bar or so, the paddle is swung back right and a flow develops as pressure rises to 8-10 bar, depending on grind and freshness.
However, since your experiment, I've persisted further and had 4 shots with a low pressure slow start on restricted flow that have still developed into really nice tasting 50-70 second, 34 gram espresso's. This is a new technique to me - leads to about 22 seconds to drip and 0.47 - 0.5 C.brew ratio.

#369: Post by **Graham J** » October 22nd, 2018, 5:10 pm

another_jim wrote:Actually, I wasn't thinking about differences in the puck head space, although Lelit's showerscreen is different from the usual one. I was thinking the needle valve in the Bianca might take up more of the available volume in the vertical part of the group above the levetta cam, so that there is less volume for the water to fill after it wets the puck but before it rises in pressure.

Ok - that area clearly also warrants some examination. I'll see if its possible to remove the cap and pull the valve without drawings and without damaging my warranty! The nylon seal edges look delicate, so I'll set some time aside and do some torque checking later this week, before removing anything.

October 22nd, 2018, 7:16 pm

Graham J wrote: However, since your experiment, I've persisted further and had 4 shots with a low pressure slow start on restricted flow that have still developed into really nice tasting 50-70 second, 34 gram espresso's. This is a new technique to me - leads to about 22 seconds to drip and 0.47 - 0.5 C.brew ratio.

Did these develop decent brew pressure? Thanks!

- Jake