This is the conclusion to a discussion that I started a couple of months ago.................

Went something like this...

Hi folks, I've recently gotten an older model 97 La Marzocco Linea AV. I would like to put some flow restrictors in but have heard that the AV models weren't really designed to be restricted too much. I don't particularly need the volumetrics, but also don't really want to do any drastic modifications along the lines of re-routing tubes etc.
I'm wondering if anybody has installed .8mm or .6mm gigleurs and what results they obtained, a parts list I got from the local distributor shows a .8mm gigleur only for the AV, but I'm wondering if it would make that much difference from the stock setup which is only moderatly restricted by the flowmeters, equating to 1mm.
Any advice or knowledge in this area would be appreciated.
Troy

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are the gigleur's part 6 in the image?

Troy said:
Hi again, just bumping this back to the main page as I'm sure there are plenty of Linea users out there.
Yes, it screws into the tube between the flowmeters and the group. I think this diagram is of an EE group through. Different arrangement for the AV. I've also heard this can be tapped into the dispersion screw at the group. I recently descaled the groups and I think the scale buildup was working as to restrict the flow, as the water flow from the group is pretty crazy at present.
Is there a specific problem you are attempting to fix? What are you trying to achieve? Clearly you feel like there is too much water coming through your groups, but why do you think this? Providing more information would be useful.
Hi Brady, Initially I had a small leak which was coming from the group cap. The groups got pulled apart and descaled and put in new gaskets and o-rings. Leak was now fixed, but in doing so the flow from the group seems overly high to a point where the water seems to curl up around the bayonet when flushing. This could be something else that I have yet to diagnose, but I thought If I could restrict the amount of flow that the water might not be so turbulent at the group. This is a stock Linea from 1997, and I don't believe it has any gigleurs installed, I guess what I want to know is if anybody else has gone this route, from having nothing to gigleurs and their results.
I have previously had experience with EE FB70's and the newer La Marzoccos with gigleurs standard, and the Linea seems to just have far too much flow, or is this just how these machine are?

Brady said:
Is there a specific problem you are attempting to fix? What are you trying to achieve? Clearly you feel like there is too much water coming through your groups, but why do you think this? Providing more information would be useful.
I have done the install with a set of 6mm gicleurs to one of our two shop machines. I really like the effect, and have a set on order to for the other machine.

with the linea av the going theory is that the flowmeter is intended to be all the flow reduction it would need.

Not so.

What I did to install them was to remove the tube and simply tap it with a machine screw I found with the same thread count and pitch. worked just fine. way cheaper than a tap. just remember to use lubricant, and only turn it in 1/4-1/2 of a turn before backing it off.

after the tube was threaded all that was left was to thread in the gicleurs, and disconect the flowmeters.
easy as that.

I did end up with one group flowing MUCH, MUCH slower than the other two, either I recieved the smaller gicleur, or I accidentally crimped it shut when I screwed it into the tube with a pair of needlenose pliers.

I LOVE the results in the espresso.
a) espresso extracts much more smoothly, little to no "glugging" or surging as the portafilter suck in air
b) espresso now "preinfuses" for around 7-8 seconds before beginning to flow
c) more body, better color, more complete extraction

downsides
1) requires longer flushes to acheive stable temp, and maintain clean screens
2) as a result ot the above requires more frequent backflushing (not a big deal)

I say go for it! I for one think the linea does well with a slower flow rate. the gicleur install at least halved the flow.

chris
Thanks Chris,
This is the sort of response I've been waiting on. I've also just talked to a Marzocco technician though who seemed to think it was unnecessary, however positive results speak volumes to me and I might just look into doing the job.
I'll first disconnect the tubes to see if I actually already have the gigleurs in there or not, will be much more painless to just swap existing ones out, however it seems that they weren't generally shipped this way.
Anyhow, I'll have a look tonight and see what I've got.
Thanks for the informative response.
Regards Troy.

chris ganger said:
I have done the install with a set of 6mm gicleurs to one of our two shop machines. I really like the effect, and have a set on order to for the other machine.

with the linea av the going theory is that the flowmeter is intended to be all the flow reduction it would need.

Not so.

What I did to install them was to remove the tube and simply tap it with a machine screw I found with the same thread count and pitch. worked just fine. way cheaper than a tap. just remember to use lubricant, and only turn it in 1/4-1/2 of a turn before backing it off.

after the tube was threaded all that was left was to thread in the gicleurs, and disconect the flowmeters.
easy as that.

I did end up with one group flowing MUCH, MUCH slower than the other two, either I recieved the smaller gicleur, or I accidentally crimped it shut when I screwed it into the tube with a pair of needlenose pliers.

I LOVE the results in the espresso.
a) espresso extracts much more smoothly, little to no "glugging" or surging as the portafilter suck in air
b) espresso now "preinfuses" for around 7-8 seconds before beginning to flow
c) more body, better color, more complete extraction

downsides
1) requires longer flushes to acheive stable temp, and maintain clean screens
2) as a result ot the above requires more frequent backflushing (not a big deal)

I say go for it! I for one think the linea does well with a slower flow rate. the gicleur install at least halved the flow.

chris
troy,
I really don't think any of the AV models came with any gicleurs, or the threads to put some in. the theory as I said was that the inlet to the flowmeter would be restriction enough. when you do it let me know how you like the results, I suspect you will really like it. It opened up some new flavours to me. being a more gentle extraction i found I could use a finer grind, thus improving the extraction bringing deeper more complex flavours and richer pigment extractions.

the job itself is pretty straightforward.

best of luck,
chris
Troy,
You can add pretty much whatever restrictor you want. on the Av lineas the Flowmeter was the original restrictor (about 1.2mm). Current production has added the 0.6mm restrictor. The flowmeter (made by Gicar) is designed fro a particular flow tare with the 1.2mm orifice. This design is to get perfect results. With the 0.6mm orifice you suffer about 5% error in the flow meter. Nothing that you will notice. The 0.6 mm orifice will slow the flow of water until the filter basket is full. Then the coffee is a bigger restrictor so after this is does not matter what orifice you have in there. In other words it only affect thi 1st 5-6 seconds of the shot (but it is a very important part).


Bill C
Thanks Bill,
That clears up a few things for me.
I haven't added any restrictors as yet, do you think the restrictor screwed into the dispersion screw would be effective? or am I better to go with the traditional placement in the tubing between flow meters and group.
As for my other sideways flow issue, remedied by bending the dispersion screens ever so slightly. They looked cosmetically fine, but had obviously been flattened out by coffee expansion and really effected the path of the flow through the screens.
Troy

Bill Crossland said:
Troy,
You can add pretty much whatever restrictor you want. on the Av lineas the Flowmeter was the original restrictor (about 1.2mm). Current production has added the 0.6mm restrictor. The flowmeter (made by Gicar) is designed fro a particular flow tare with the 1.2mm orifice. This design is to get perfect results. With the 0.6mm orifice you suffer about 5% error in the flow meter. Nothing that you will notice. The 0.6 mm orifice will slow the flow of water until the filter basket is full. Then the coffee is a bigger restrictor so after this is does not matter what orifice you have in there. In other words it only affect thi 1st 5-6 seconds of the shot (but it is a very important part).


Bill C
Troy,
It must be added in line with the plumbing. You need this thing in the water path before the valve. If it is after, (in the dispersion screw) it will also restrict the exhaust flow. The Exhause would probably plug up this part also. If you need help knowing where to install this let me know.

For the dispersion screen, this "flattening" usually occurs from "too much" coffee in the basket. It is usually not form teh expansion of the coffee but the installing of the portafilter when there is extra coffee in there.

The rule of thumb for LM machines is the Max imum amount of coffee in the bashet will just reach the dispersion screw. If you install a full portafilter, then take it out, you should see a small indentation of the screw in the coffee cake.


Bill
So, I've finally gotten around to installing the flow restrictors in my Linea over the last few weeks.
Thanks again for all the help and advice from both Chris and Bill. The relatively easy modification, has made a tremendous difference, and my extractions both look and taste as I always knew they were capable of.
I have found like Chris , that I can grind a little finer now and channeling is definatively a non-issue.
I have left the flowmeters in the equation, but haven't noticed any significant difference in the accuracy of the volumetrics. I generally only use the manual brew switches anyhow.
One of the groups did have a low flow issue after the install, which I believe was related to a small piece of scale getting lodged somewhere, but after disconnecting all the copper tubing and descaling properly(Which I should have done in the first place), the problem was remedied and both groups now dispense around 60mls in just under 10 secs with empty portafilters.
I'm pretty happy with this and wouldn't hesitate to recommend doing the job to anybody with an older AV Linea.
The size I ended up going with were the 0.6mm, as thats what the new machines are shipping with and it provides a perfect buffer to gently introduce the pressure with a good 5-6 sec preinfusion of sorts.
Troy
Great! Thank you very much for following up on this.

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