LObin wrote: Can't be fed from a flojet system.

But from an Aquatec system. They have various models that can provide a variety of pressures.

LObin wrote:Of course if you use a pump capable of 5 bar pressure and all the other stuff, then you can feed pretty much any machine from a fish tank

Per Londinium, the Compressa requires a line pressure of minimum 3 bar. That's the information I was trying to pass.

Gotcha

LObin wrote:I haven't no. My L1 preinfuses at boiler pressure, just like a Faema Lambro. Back when I had the Bezzera HX lever, I don't remember trying anything above 3-3.5 bar.

Agreed 6 bar (even 5 bar) is not preinfusion. Might as well have line pressure up to 8 bar to achieve full 8 bar preinfusion.. The only way to pull the lightest roasts, otherwise your missing out on flavor

If you look at graphs of decent, they often go to 4-6 bar of preinfussion and pause. It has effect for sure. You may call it whatever you like.
It depends on coffee and for example for filter roasts 4 bar it can boost the acidity or boost darker taste (versus 3 bar).

For those still wondering about running dark roasts through the Londinium R due to higher temperatures, I ran a quick test this morning:

I pulled 3 identical shots, 1 at 3 bar, 2 bar, and 1.2 bar. All for 3 second preinfusion, aiming for just under a 1:2 ratio (adjusting the grind accordingly and using a 14g dose). The coffee I used is Filicori Zecchini Delicato. It's a northern Italian blend, darker than most drink here, but not as dark as the stuff typically drunken in Naples and the south.

The 2 bar and 3 bar shots were very close. Both had heightened body, and a more punchy, less rounded taste. The finish was more bitter than the one pulled at 1.2 bar, but still quite good. I actually liked the front end of the taste from these shots better than the one at 1.2 bar. I'd imagine these would actually work better in milk drinks.

The one at 1.2 bar was probably the best of the bunch. It had heightened sweetness, the least bitter finish, but with slightly less body and punchiness. The sweetness, roundness, and delicate texture was almost a little too much for my tastes. I tend to like shots that are well balanced but punch you in the face, so to speak.

All were good shots, none were bad. So bottom line: yes you can run dark roasts without screwing around with anything. And the whole temperature thing may have a small effect, but is a bit overblown IMO. The important thing is consistency, which the LR has.

mathof wrote:Thank you for your clear reply. I had not realised how much the LR differs from my old version of the L1, in which the brew water does share the same circuit as the water that warms the group. I have a restrictor in my thermosyphon, somewhat wider than the original diameter, and I have assumed that has increased PI pressure above the 1.4 bar the pressurestat is set to. Would I be right about that?

Now that you mention this, I can't be totally positive. I thought that thermosiphon loops were always distinct pathways from brew channels (although both coming from the same boiler), so perhaps I'm just not informed here.

Joshua,

Madman13 wrote: II bought a replacement group cap
image

Sorry for responding to a year-old post, but I'm expecting my Compressa to be delivered next week and was thinking about doing this mod but don't want to drill out the original group cap. Reiss didn't know the exact spec of the group cap, and doesn't carry it as a purchasable item.

Do you have the specs for the group cap? Where did you get yours?

CoffeeMac wrote:Joshua,



Sorry for responding to a year-old post, but I'm expecting my Compressa to be delivered next week and was thinking about doing this mod but don't want to drill out the original group cap. Reiss didn't know the exact spec of the group cap, and doesn't carry it as a purchasable item.

Do you have the specs for the group cap? Where did you get yours?

Hi,

This is the group cap I used

https://www.espressoparts.com/products/ ... 4547654843

Chrome plated brass, super easy to drill and tap.

You'll also either need to buy a new copper gasket or take the old one and hold it with a pliers and hit it with a blowtorch until it glows red, then let it cool off slowly to reanneal it

Thanks!

How has the mod worked out for you? Useful day to day? Any issue with disrupting the thermosyphon?

Love it, it is more useful then I originally thought it would be. It shows both preinfusion pressure and pressure build up as you release the lever all the way up to the beginning of the shot (which helps with slow pressure ramps, etc). There is no effect on the thermosyphon.

Well, I just installed mine this afternoon. Can't wait to see how it works in the morning!