Pre-infusion solution for the Mini

[Cliff]

I received the solution for the Mini today and was able to install it to night. It was very easy and only took about 20 min. from start to finish. Seeing that it is so late I only pulled 4 shots and I did not taste any of them. The first pull was a blank shot. I could tell no difference in the pressure with the Pre-infusion chamber in. So I put 14g in the basket set the timer and pulled the 2nd shot. In exactly 8 sec. the shot appeared and in was oh so pretty. For the 3rd and 4th I thought I would do a comparison I stopped the 3rd shot and 4 sec. and the 4th shot at 7.5 sec. so that I could inspect the puck. The pictures are not the best and I will take more later. I will also take a short video as well. The light tan puck in the picture was the 4-sec shot. The water made it exactly half way through the puck. The 7.5sec puck is the darker one. The water made it all the way thorough the puck. I will do some taste test tomorrow morning but I do have to work so I won't be able to play around with it allot until Sunday. For now it does exactly what was designed to do. I am very excited to wake up in the morning for the taste test.

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[Cliff]

I have been chasing my local coffee shop's shot for a few months now and have not been able to duplicate the taste of there shots. I have came close but just as I thought I was there I could not duplicate it. Using the same temp, grind, and dose I just could not get it correct. The main deference was the machine. They use the Synesso.

I can gladly say that this morning was the closest I have came yet. I am very happy with the Pre-infusion chamber with the mini. I don't see why anyone would not put this on there machine. I only had a chance to drink two shots before I headed on to work but it was enough to convince me. Don't get me wrong it is not a night and day difference but I think it is safe to say that the two shots where as good if not a little better than the previous best shot that I have ever pulled.

The most improvement was in my wife's shots. I hate to say it but she really does not care when it comes to dose and tamp. I try to walk her through it but it does not seem to matter. She drinks 100% milk drinks and I don't think she has ever pulled a shot that did not have channeling. Until today.... Her shot looked very good and no channeling. I can not comment on the taste of it though as I was walking out the door.

So my first impression is subtle difference in taste, but huge difference in consistency.

Sunday I will be able to spend more time with the machine and pull several shots for taste and consistency.

[admin]

BTW: Cliff's our Beta tester for this solution. It's not actually on sale quite yet.

[Niko]

That's enough to convince me to install that mechanical version on my S1

[Weska]

Thank you, Cliff, for presenting all the information on the appendix pre-infusion device--and so quickly. You are making me more eager (and I was already enthusiastic).

[zoey]

Honestly, I haven't been keeping up on the reading regarding the pre-infusion for the Mini. It appears that the attachment diverts water from the group head before allowing it to continue to the PF?

If this is the case, I have a few questions:

Being that the diversion tube (sorry if this is an incorrect term) is out in the open, does it cause any significant decrease in water temperature, which would necessitate insulating the diversion tube.

How do you adjust the time of the pre-infusion for longer/shorter durations? Is it a board program?

Any idea on what the final cost of the device will be?

[chas]

Honestly, I haven't been keeping up on the reading regarding the pre-infusion for the Mini. It appears that the attachment diverts water from the group head before allowing it to continue to the PF?

Actually it diverts water and water pressure from the group until the piston reaches the end of its travel, then full pressure is applied to the group. When the 3way opens the water in the cylinder is forced out the 3-way, it never ends up in your shot.

If this is the case, I have a few questions:

Being that the diversion tube (sorry if this is an incorrect term) is out in the open, does it cause any significant decrease in water temperature, which would necessitate insulating the diversion tube.

No.

How do you adjust the time of the pre-infusion for longer/shorter durations? Is it a board program?

You don't. It's like the preinfusion used in most E61 HX machines. It is what it is. No adjustments. The main difference in the version on the Vivaldi is that if you don't like it, you can remove it.

Any idea on what the final cost of the device will be?

Chris says $75ish. At least that makes it high enough to qualify for free shipping.

[zoey]

I see that I need a little remedial instruction on how the Mini functions.

I guess I thought that the shaker pump sends the water to the group head by providing the pressure, which can be adjusted via some type of reducer valve. I thought the purpose of pre-infusion was to 'pre-soak' the coffee, which allows an enhanced flavor to be extracted?

So, the water comes from the shaker, through the reduction valve (if that's what it's called), to the piston located in the pre-infusion add-on. When the piston reaches full travel, it then forces the water through the group head and then through the PF?

I know I have this all wrong. When does the pre-soaking of the coffee occur?

At one time I thought I read that pre-infusion was used in machines that couldn't develop sufficient pressure, which helped to improve a rather lacking machine?

[chas]

It's all hydraulics. When the pump turns on, the pressure starts to push the piston down the cylinder against a large spring. During the 3-4 seconds it takes to hit the end of the cylinder, part of the water pressure is being diverted to push the water down this 2nd path and part of it - at a lower pressure - is moving through the puck. When the piston hits the end of the cylinder all the pressure is then applied to the puck.

Compare it to putting a cheap "Y" valve on the end of a garden hose. Open both Y valves and half the water at half the line pressure comes out of each opening. If you close one side of the Y valve all the water at full line pressure then comes out the one remaining opening.

[zoey]

I like your analogy! Thanks! Now it makes sense to me.

[Cliff]

Ok I was able to spend some time this morning with the machine I pulled 15 shots. I want to start off saying that this is not the cure all to bad technique. In my previous post I may have made it sound that way. The wife and I just happened to pull some really good first shots. I did have some channeling in some of my shot that I made, but the good thing is that all 15 shots where very close in taste.

For the first few shots with the chamber install I left my machine where I had originally had it (pre-chamber) setup for a 2oz 30 sec. shot . After I pulled the first shot with the chamber in the shot lasted 34 sec. and only pulled a 1.5 oz shot. So I dialed in the grinder and change the volume of water for the double shot button.

Before the chamber was installed my shots when using Barefoot where just a tad bit on the bitter side. With the chamber in place it is now on the sweet side. If I had to put the shot in my own words I would call the shot smooth and sweet. For my taste it is perfect but I think some will think it is to sweet. It is easier now to taste the different flavors of the coffee. If you remember my wife only drinks milk based drinks. After her first taste of her latte she said that the chocolate flavor really came forward. I also made my self a latte. It was very good but it seemed that the coffee did not stand out as much now. I think this has something to do with the 14 other shot that I have pulled and tasted this morning. I will make a latte later in the day and compare.

I have some CC Toscano that should be here Monday so I look forward to trying a different blend with the chamber in.

Below is a video of one of the shots that I made. I tried to get the manometer in the shot as well so that you can see what is happening with the shot.

Here is a link to the video http://www.vimeo.com/1213290

[chas]

You can use a link to an external video but you can't embed HTML code into a post.

I concur with your comments about packing the PF. Preinfusion can solve minor packing/tamping problems but not significant ones.

[Cliff]

Thanks Chas. http://www.vimeo.com/1213290

[JohnB]

The Toscano is prone to channeling more so then other blends I've used recently so proper distribution is critical. With the last couple blends I've used I was able to fill the p/f, level & tamp. With the Toscano you will be seeing some impressive squirters if you don't stir before tamping. It will be interesting to see if the P/I lessens this problem.

[chas]

Cliff, I can tell by listening to the pump and looking at the PF pressure gauge that you are getting 6 sec of preinfusion. When the piston gets to the end of its travel, the sound of the pump changes and, as the pressure quickly ramps up, the needle also starts vibrating. It appears that the spring loaded piston is acting like a shock absorber on the Mini and preventing the needle from vibrating until it hits the end of its travel.

It makes me wonder if other vibe machines have some sort of water shock absorber system that prevents their gauge needles from vibrating.

[Cliff]

Chas, you are you are correct. I took another puck picture one at 3 sec. and one at 6 sec. The 3 sec. pull made it almost half way through. The 6 sec. almost made it all the way through the puck. Seeing that it did get the sides it is probably a dose and tamp problem on my end.

[zoey]

More stupid questions from me:

So, the water pressure from the vibe pump pushes back a spring within the tube. Once the spring is at the end of the travel, it re-expands, pushing it's water back into the flow of the group head.

Let's say it takes 7 bar to begin moving the spring back. At the end of travel, is that pressure increased due to compression? I'm trying to understand what allows the spring to re-expand? In my mind, it could only do so if the pressure to the spring were to fall below 7 bar.

I know it's all hydrodynamics and math (both of which I know nothing about).

[chas]

The spring stays squashed at the end of its travel until the pump shuts off and the 3-way valve opens. Then it rams about 1/2oz of water out the 3-way.

[zoey]

Ok so, using the Y-hose descriptor, basically the tube decreases the pressure of the water reaching the puck; thus causing the water of one leg of the 'Y' to 'trickle' into the puck v.s. being 'shoved' through, hence causing pre-infusing the coffee. The water from the tube never reaches the coffee.

Stay with me on this. If it hasn't become apparent, I have a learning disability from being dropped too many times as a kid.

[Richard]

So, the water pressure from the vibe pump pushes back a spring within the tube. Once the spring is at the end of the travel, it re-expands, pushing it's water back into the flow of the group head.

No. Once the spring/piston assembly has traversed to the end of the chamber, it remains there for the duration of the shot, until the pump is turned off and the three-way valve releases

Let's say it takes 7 bar to begin moving the spring back.

Let's say more like two or three bar. I'm guessing here, but it's going to be relatively low.

At the end of travel, is that pressure increased due to compression?

During the time the spring is uncompressed, i.e., during the compression period when the pump is first turned on, it is the tension of the spring which determines the pressure on the puck. After the spring is compressed and the piston has traversed to maximum deflection, the pressure then ramps up in the normal manner to whatever the machine is set for.

I'm trying to understand what allows the spring to re-expand? In my mind, it could only do so if the pressure to the spring were to fall below 7 bar.

When the shot is over, the pump is turned off and the three-way valve opens, releasing all pressure. The spring will decompress, probably with some rapidity and likely causing a noticeable WHOSH out the exhaust into the drip tray.

[Cliff]

After using the chamber now for a few day

[Mario]

I am posting this as a warning to other Mini owners who might be as mechanically inept as I am. The instructions you get are really not geared towards the Mini and there is a step missing, albeit its probably one that any ordinary person would assume (but it took me 10 minutes to figure out).

I ordered the kit on Friday and it arrived today - very quick service. I gathered the necessary tools ,etc. First there was a trip to Home Depot to get Teflon tape and a hex wrench. I had no idea what the Teflon tape was or how to use it. Luckily I asked the HD guy and he explained that you wrap the tape a couple of times around the thread BEFORE you screw it in. (OK - you're getting a sense of my lack of mechanical ability) I followed the directions VERY carefully. The required time said 20 minutes but for me it was about 80. There was one 10 minute glitch I think due to the instructions being geared towards the VI and VII. The instructions tell you to remove the screws that hold the front control panel on and then gently pull the front panel out from the machine and lower so you have access to the group. However for the Mini there is a missing step: Before you pull the panel out you must unscrew the steam paddle knob from its stem. You very simply do this from the front and it comes right off. I am risking insulting the intelligence of every other member here as this might seem obvious. But I spent 10 minutes wondering why the panel did not slide right off. For a while I was contemplating a much more complicated procedure involving taking the entire steam assemble apart from the casing. I took one screw off and when luckily it dawned on me that all you have to do is unscrew the paddle knob. The panel is still connected to the unit by a wire but it can be lowered to provide access.

I must say the rest of the procedure went fine. For a person of my limited ability it was a miracle everything worked out OK but it did. I would have to say if I can do it just about anyone can.

I've pulled a few shots and everything seems great. Its hard to really asses what difference is occurring but it seems to me the stream from the naked portafilter is cleaner and more cohesive. The change also seems to add some "dimension" to the shot taste. There seems to be a slightly more complex taste although my wife thinks I may be imagining it to justify the installation.:) It is subtle but I think there is something there and the the shots do seem more consistent. The hot weather was creating a lot of clumping which in turn was giving me some channeling and squirting. But the pre-infusion does seem to help.

I do have a question about how the pre-infusion might effect grind setting and pull time but I'll post that separately.

Brava La Mini!

Mario

[Mario]

Here's what it looks like BEFORE and AFTER taking the knob off. This will allow the front control panel to slide off properly.

Mario

[oton]

I'm wondering if 6 sec of Preinfusion isn't too much? Why La spaz decided to adjust it to 6, instead of 3 or 4?

[Endo]

The 6 seconds seems just right to me. Less would not soak the puck adequately.

They could have easily went with less, and it would have meant the chamber would actually be smaller and cheaper.

I suppose you could always remove the c-clip on the back of the chamber and add a washer/spacer if you wanted shorter times. That wouldn't be possible if it was smaller.