Plead for help with sour shots (Reneka Single renovation) [Solved]

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Ludvig
Posts: 13
Joined: 11 years ago

#1: Post by Ludvig »

Hi everybody!

I'm coming here, to the best coffee experts there are, hoping you can help me with a complicated (for me anyway) problem.

I bought a Reneka Single some time ago and have restored it to fully functional (OPV, Pump, de-scale... only things left are water flow meter, gicar box and the 3-way valve).
I have an Ascaso Steel I1 grinder (and an old Santos 6a).

Old problems:
I have had some problems with the group head though, the (water dispensing) bolt holding the shower screen was sticking out an awful lot (like 3 millimeters) and made a hole in the puck so I limed it off.
Then there were eroding because of the 'middle' (a 'ring' between the centre and the circumference) of the shower screen touched a protruding part of the group, containing the water to the center of the coffee puck. So I made a quick fix adding another shower screen and got rid of all channeling and erosion (the water travels well between the two shower screens).

This is what I have been able to measure:
Pump pressure with a (slightly leaking) blindfilter is about 9.5-10bar, I have tried a bit less and a bit more.
Temperature is about 94-96°C (201-205°F)

When I do my shot:
I grind, fluff up the grinds, pour them in the filter, do a WDT and tamp with mild to medium force in a N-E-S-W manner.
I do my HX flush, wait 25 seconds (or else temperature drops a lot during the shot) and invariably pulls a very (very!) acid shot.

Result:
It is short and acid and if I grind less, sure I get more coffee but it blonds really fast, too fast whatever I do.
I have bought coffee from 3 different roasters, beans that were de-gasing, keeping them in an air tight container and used them from 2 to 7+ days after purchase.
I got less or more acidity but even the best clearly was really too sour (no kidding).


So I searched for another culprit and stumbled on the explanation that I don't use enough coffee, I use from 11,5 (less and it gets too soupy) to 13,0g (more and the screen hits the puck).
But it seems a bit exaggerated that I can't pull even a bad espresso on my machine with 13g, right?

I haven't changed the 3-way valve, it seems okay though but can I be sure / would it be possible for a broken 3way valve to make the shot sour?

So, please, espresso gurus out there, what should I do now?
Any help greatly appreciated, I'm so stuck!

Tom@Steve'sEspresso
Posts: 462
Joined: 15 years ago

#2: Post by Tom@Steve'sEspresso »

Wow I'm surprised nobody has answered yet.
I would attempt changing the temperature of your machine slightly in both directions, a bit hotter in small increments and a bit cooler in the same manner, to see if your flavors become more favorable. I recently fired up my rebuilt Rancilio S10 lever and set it to 1bar which was what i thought to be an ideal temperature until I tasted the very sour shots. In the end I had to bump up the pressure to 1.1 bar- a small change for a big difference in taste. The other factor in your equation may be your grinder...need new burrs? I'm really not familiar with your brand so it is hard for me to comment.
LMWDP #222
Live graciously
Be kind
Have fun

Ludvig (original poster)
Posts: 13
Joined: 11 years ago

#3: Post by Ludvig (original poster) »

Yeah I started to despair :P thanks!

I will definitely keep in mind that a small 1-2C° change (if I remember correctly 0.1bar is 1 or 2 degrees Celsius) can make a big change and I'm trying my best to do the HX-flush correctly. I'll try upping the temp in reasonable amounts (see below)!

The burrs should be OK in the Ascaso and I also have tried with a Santos with new burrs and nothing really changed.


As it just "doesn't work at all" (it really is sour!) I have tried most things I could think of like quite hotter temperature by just do a mini-flush and then go (but I think that probably led to channeling, water was probably boiling at some moment), grinding much coarser (mucky puck and thus channeling).
As it is a French machine I also tried the "French espresso", the 3/4, and just chucked in normal ground coffee, tamped almost nothing and out came (in, like 5-10sec), ordinary coffee. So the machine seems to be able to do that anyway...

I still suspect that there is some weird channeling going on because of this:


There is no dispenser screen (which is "normal") and the mark on the shower screen perfectly matches the protruding part in the group head.

I chucked in a second shower screen and got better results, no visible channeling but I still think it occurs (or water traverses the coffe in a non ideal way, say much more in some places) so I have removed the double and made a ring of wire to distance the shower screen from the group instead, haven't had time to test though, hope I can do that tomorrow.


ps. the photo of the group is old, it is a bit cleaner nowadays.

Ludvig (original poster)
Posts: 13
Joined: 11 years ago

#4: Post by Ludvig (original poster) »

I made a ring (~57mm) of quite thick wire (maybe 1 mm) and put that between the group and the showerscreen and ... miracle! I can make non-channeling drinkable coffee!

Sure, the shot isn't that okay yet but hopefully I'll just need to dial in the right values and work on my 'barista' skills now :mrgreen:

witoldb
Posts: 36
Joined: 11 years ago

#5: Post by witoldb »

What is the water path?
I can't see any holes in your diffuser plate.
Can you confirm your parts No's referring to diagrams on cafeparts site?

User avatar
Rikinwa
Posts: 141
Joined: 11 years ago

#6: Post by Rikinwa »

Lidvig,

I have been using a Reneka Viva 1 at my office for a couple of years now. It does a really, really good job (and, I'm mostly a lever snob with Olympia Cremina and Elektra Microcasa a leva at home - :-)).

I do think that your machine needs a different shower screen maybe.

Here's what the setup looks like on my machine.









Rick