orphanespresso wrote: The lower part of the rod is 1/2 round and no matter what orientation it is installed the functional opening of the passage between the upper and lower TS pipes in the back of the group is the same. The nut can be shimmed higher and lower but again, when looking at it this seems to not make any difference. So I don't think the TS is adjustable with this rod and can't find any other smaller rods to install to allow a faster flow. The metering rod seems to act as a restrictor and I assume it is remove able mainly for descaling/service or replacement if it gets corroded.
Also, it may be that to manufacture the group they may have drilled from above to create the passage for the TS service and then added the restrictor rod and top cap to finish the drill hole. Just a theory.

I often miss English words to explain my though so thanks to you Doug as this is exactly what I think too about this group design

Thanks Pascal!

Here is an update.

A group thermometer was a great help and combined with the Scace and confirming everything by taste, I am very happy with the outcome. This is pretty cool.

I played with the boiler pressure from 0.5 Bar to all the way to 1.1 Bar (the point where it kicks in). I found out that using lower boiler pressure I wasn't getting enough pressure for preinfusion. A clue was lever raising almost completely vertically after release. I raised the pressure to cycle between 0.62 and 0.8 Bar. At this pressure the group is coasting at 178F pretty much all day long. After a lot of testing I figured out that I need the group to be at 175F - 176F to produce the sub-200F shots I like. If I insert a room temperature portafilter, the group goes down to 175F -176F in two minutes, enough time for me to prepare the basket. If I don't insert the portafilter, the group stays at 177F - 178F. It works like a clock. It is much easier then Cremina, where I have to rinse and reinsert portafilter 2 or 3 times to get the temperature down (although I often just turn the Cremina off between shots with the cold portafilter in the group and the group cools down in 10 min or so. I do it at the consulting site.).

With this routine I let the group coast at 178F, insert a room temperature portafilter in, prepare the basket, insert a bottomless portafilter with the basket, do a 15 sec preinfusion (I know it is long preinfusion, but I need a longer preinfusion with the lower boiler pressure), preinfusion starts at 199 - 200F, raise the lever, extraction starts at 199 - 198 and goes down to 193F. At this point the group temperature is at 178 - 179F. Without any delay I can insert a room temperature portafilter and pull another shot in 2 minutes, enough time to dump a spent puck, wipe the screen and the basket, grind some coffee and prepare a new basket. I can do back to back shots all day long with basically no shot to shot difference (1F - 2F max).

So if I want a cooler sub-200F shot, and I am pulling a shot after machine has been idling, I walk up to the machine, insert a room temperature portafiler, prepare the basket, pull the shot. If I want a hotter, 200F - 201F shot, I don't insert a room temperature portafilter and pull the shot.

This is pretty awesome if you ask me. I am done testing and removed my group thermometer and mount it where it belongs, on Cremina.

Hello Vlad
That is certainly some impressive research you have been doing on the Lambro! I've done some of the same, but didn't have the scace, only a temp probe that I inserted in the portafilter. Unfortunately it isn't fast enough for measuring temp variations during shots, but I used it to test whether adjusting the "thermosyphon-rod" on top behind the group made any difference to the idle temperature of the group and couldn't really observe any difference, no matter how it is orientated. I had long periods 15-20 minutes in between adjustments to allow for equilibration. So I think Doug is right, it must have another purpose, or maybe you need other rods of greater size to get an effect.
Another observation similar to yours is that lowering the group temperature, compromizes preinfusion in a way that it affects shot volume. I think this is due to the remaining trapped air in the group being less compressed by the lower pressure, hence, less space for water to fill the group. The equilibrium I would assume, takes less than 15 secs, I don't get higher shot volumes if I change preinfusion from, say 8 to 15 secs, but you're right, the temperature will drop more..
I have my boiler pressure set at 1,1-1,3 bar to get acceptable shot volumes, my lever will kick in at about 110 degrees upstroke, I think. If you want to have an earlier "catch" of the lever, you can try not inserting the lever entirely, when you lower the lever, water will flow out, and you quickly lock the lever completely, this gets rid of some of the trapped air, and allows for a greater shot volume, and more importantly in my view, that you get another pressure profile with higher pressure from the spring due to it being more compressed when it kicks in.
It is difficult to explain, I don't know if you get what I mean, I hope so
Keep posting!
Best regards
Ulrik

Hi Ulrik, thanks a lot!

"I don't get higher shot volumes if I change preinfusion from, say 8 to 15 secs". In my case, higher shot volumes weren't the goal. I can get a full double with a normal 7 - 8 second preinfusion. I usually go for 18 - 20 gram ristretoes, so shot volume is really not an issue. I was going for a fuller puck saturation during preinfusion. With more puck saturation I get picture perfect extractions every single time. There is no point of watching anymore, but I still do because it is mesmerizing.

I think you get those nice extractions through prevention of channeling.

With a careful Fellini move, you can get that early expansion/preinfusion phase a bit quicker and thereby do it at a higher temperature and allow longer extraction phase before overextraction. One should thereby also be able to prevent any channeling. It would effect the flavor of the shot as well. Next time I fire up my big machine, I wish to experiment in that way.

I pulled my first shot of the day with a 65 C group using a quick Fellini move to shorten the preinfusion and try to raise the shot temperature relative to that still cool group. I enjoyed the bright tangerine/cherry flavors of the shot of Stumptown Costa Rica Marvin Robles. They were not muted like I would expect from the cold group.

I have an insulating sleeve that I wrap around a group to expedite warming and to bring the group temperature. Without it steady state temperature is app 77C but today I left the sleeve on and extracted the same coffee with 20 sec preinfusion. I believe that allowed the extraction temperature to come down which prevent bitterness for a very tasty albeit bright americano ripe with tangerine and cherry flavors.

A somewhat cool group can make a warmer shot with brief preinfusion. A hot group can make a somewhat cooler shot with prolonged preinfusion.

Do you think this is correct?

Yes of course ! Many people think pre infusion only serves to moisten the grind, I believe and tell since a while that it is mostly like a temp surfing for lever groups.

Another thing for lever groups, available for HX groups (true ones, I know Lambro is false HX)... I miss (one more time) some English words to explain my though about flushing the group before making an espresso to cool water temp. But I think since a while that there is another way on well designed HX groups to surf temp than throwing water into drain... An adapted temperature of the steam boiler's water with a correct level, both depending on temp profile needed for a given coffee, has the same effect than a too hot steam temp with flushing water til it stops being too hot...

Another thing for lever groups, available for HX groups (true ones, I know Lambro is false HX)... I miss (one more time) some English words to explain my though about flushing the group before making an espresso to cool water temp. But I think since a while that there is another way on well designed HX groups to surf temp than throwing water into drain... An adapted temperature of the steam boiler's water with a correct level, both depending on temp profile needed for a given coffee, has the same effect than a too hot steam temp with flushing water til it stops being too hot...

Pascal,
Just to understand this. Not being a true HX, would the above NOT apply to the Lambro, then?

Yes Niels it is the same thing on Lambro, even if it isn't a true hx.