Bezzera Strega Mods: effect on taste and workflow

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BKH
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#1: Post by BKH »

OK, I don't have any experience with any of the mods as my Strega is still stock but I have been impressed and am curious. What mods, for those of you who have done them, do you like the most and why? Which ones were worth the effort? I'm thinking about the effect of removing inner spring, pressure gauge for preinfusion, and the pump flow control mods but happy to hear about others

I thought there could be a thread to share some of the user experience of the mods outside of their excellent how-to's.

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baldheadracing
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#2: Post by baldheadracing »

These are the ones that I've done:

Pre-infusion pressure gauge - definitely recommended but I haven't drilled a hole in the case to accommodate the gauge; I want to be able to return the machine to stock before selling the machine.

Dimmer mod on pump - had it but removed it as the pre-infusion pressure gauge showed how much variance there was. I have found it easier to just lift the lever handle to turn off the pump when the desired pre-infusion pressure had been reached.

Noise reduction - FWIW, here's the pump noise that I've measured during an extraction, right beside the group:
82db - stock Strega;
75db - Quick Mill Pulsor installed on the pump, pump mounts upgraded, pump output line switched to braided stainless steel from a Silvia. This was noticeably quieter, but more importantly, the Pulsor removed the harsh abrasiveness of the pump noise;
51db - Lined the inside of the case clamshell, water reservoir surround, and parts of the bottom of the chassis with 1/2" silicone closed-foam insulation. As a bonus, the water in the reservoir gets nowhere near as hot as it used to.

I haven't removed the inner spring but it is "on the list" to try - and has been for quite a few years now :oops:.

ETA: I did put on the Cafelat shower screen for the Modern lever group. I also tried the Matrix screen, but I think that is more for pump machines. I also started using a puck screen because I would occasionally have uneven imprints on pucks. I currently use the SWorks 17-4 thin puck screens that work with magnets - pulling out the puck screen makes clean-up easier.
-"Good quality brings happiness as you use it" - Nobuho Miya, Kamasada

doobedy
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#3: Post by doobedy »

I've done three things to mine, and after owning it (for years) I went from lowkey struggling to tame the beast to absolutely loving it. I was going to type the mods in order of importance but they really work together:

1) PIDed the grouphead heaters. The 95C thermostat is just too damned hot for anything darker than medium. My first mod was actually just replacing this with a 90C thermostat, and those results encouraged me to go all the way because I enjoy different roast levels. This can be done for less than $50 if you order what you need from aliexpress, namely a PID, aluminum box, SSR, and thermocouple or RTD.

2) Removed the inner spring. This had so many positive effects in basket, dose, and grind size choices. Yes, the HQ14 basket or similar is the best for a stock Strega, but the reason is that it is a low flow basket, and you need all the pushback you can get against those relentless ~12 bars of pressure. Slightly convex. Less hole coverage on the bottom. And are pretty much locked into that one style of basket. Dosing below 18g or grinding coarser both present challenges too at those pressures in a 58mm basket. The shots also, to me, never had classic lever softness. And a bad shot with less than perfect puck prep could be *very* bad. Bitter, astringent and sour at the same time. Oof.

3) Finally, I got rid of the 9-bar pump. The dimmer mod would be similar but I wanted something even simpler, so I replaced it with an Ulka 2.5-bar pump rated for 100% duty, with higher flow rating, although it actually fills at the same rate because of restrictions in the path. This is equivalent to average house line pressure (with a slower fill rate for better or worse). I really don't feel the need to experiment with this particular parameter, espresso is already difficult enough. Oh, and it is MUCH quieter.

The above changes transformed the Strega from something I was constantly fighting with to a forgiving machine for light and dark roasts. Maybe similar to a Londinium R24 set to the same preinfusion pressures? But really its own thing. I especially appreciate the super quick heatup times thanks to the grouphead heaters.

One thing worth mentioning is that the lower preinfusion pressures limit shot weight to ~50g now, and I feel like I got closer to 60g with full preinfusion before the mods. Regardless, I can't recommend the mods enough. I know it takes away some of the uniqueness of the Strega, but I just want to make good coffee consistently. Or at least consistently drinkable, which to me is what a lever should be all about.

doobedy
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#4: Post by doobedy »

baldheadracing wrote: I haven't removed the inner spring but it is "on the list" to try - and has been for quite a few years now :oops:.
Have you ever seen confirmation that the spring is under pressure if you unscrew the piston? My piston was under so little pressure it could be turned by hand. I compressed it and held it with steel zip ties just in case, but it felt sort of unnecessary.

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baldheadracing
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#5: Post by baldheadracing »

Either there is threadlocker on my piston rod or the springs are under compression. I haven't investigated any further as I will retard the lever as needed to reduce pressure.

I do have the parts to PID the group, but I rarely pull anything darker than medium-light so I walk-up-and-pull or at most do a quick flush.
-"Good quality brings happiness as you use it" - Nobuho Miya, Kamasada

BKH (original poster)
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#6: Post by BKH (original poster) »

doobedy wrote:I replaced it with an Ulka 2.5-bar pump rated for 100% duty, with higher flow rating
Interesting simple idea to try different preinfusion. I suppose one could also adjust the OPV. I see the EP77 at max 4bar

https://ulkapumps.com/en-us/products/ulka-ep77-120v

Which model did you go with?

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bostonbuzz
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#7: Post by bostonbuzz »

PID grouphead would be number one. No flushing or guessing about temp, and it's a low power ssr and heater so fairly simple.

Grouphead gauge I did recently really helps the preinfusion consistency. Even without the dimmer you can stop right where you want and wait for drips to appear at any pressure.

Remove inner spring. Mine screwed off and after noticing the spring was almost slack I aimed it at the couch pillow. Didn't need the pillow :). Before removing the spring the pressure was so high I had to do tight shots and had trouble keeping on top of channeling. This is in retrospect. Initially when I took out the inner spring I had trouble and had to experiment to make it work. It made it more of a flexible machine and I still get 9 bar stopping preinfusion at 2bar.

I did a gear pump mod and a different dimmer mod. This is now last in my list of you have a pressure gauge.
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doobedy
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#8: Post by doobedy »

BKH wrote: Which model did you go with?
This one: https://ulkapumps.com/en-us/products/ulka-ep8-120v

The flow rate is double, but the tubing is so restricted (on purpose?) that the flow rate remains exactly the same once it's hooked up. Around 10ml/s. It actually might be a fun mod to let it hit 20ml/s, a step closer to dipper or line pressure flow rate.
bostonbuzz wrote: Mine screwed off and after noticing the spring was almost slack I aimed it at the couch pillow. Didn't need the pillow :). Before removing the spring the pressure was so high I had to do tight shots and had trouble keeping on top of channeling. This is in retrospect. Initially when I took out the inner spring I had trouble and had to experiment to make it work. It made it more of a flexible machine and I still get 9 bar stopping preinfusion at 2bar.
That is actually great news! This was the part I dreaded the most, and did last. On some machines you need complicated jigs to do anything involving the spring(s). I cut a hole in an old piece of plywood to clamp mine to, plus the steel zip ties. I am happy none of that is necessary.

My experience with one spring mirrors yours, as I said above. I can run an 18g VST basket now no problem, and don't have to grind nearly as fine. So much more forgiving. It really seems like so many hoops people jump through with the Strega are the result of high pressure preinfusion and extraction. Grinding fine, low flow baskets, listening to the pump change sound, etc.

Oh, and I forgot another benefit: it is NOTICEABLY easier to pull the lever.

Edit: It might be worth pointing out the somewhat obvious for other people thinking about modding, that preinfusion pressure doesn't just affect preinfusion. It also regulates the volume of air in the brew chamber, which means the higher the preinfusion pressure the higher the spring pressure that follows, and vice versa. It's all very much connected.

Marcje
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#9: Post by Marcje »

doobedy wrote: It might be worth pointing out the somewhat obvious for other people thinking about modding, that preinfusion pressure doesn't just affect preinfusion. It also regulates the volume of air in the brew chamber, which means the higher the preinfusion pressure the higher the spring pressure that follows, and vice versa. It's all very much connected.

I made a few mods on our Strega, which can be foud here.

These mods also allow me to make a 'blooming' shot (pre-infusion without pressure, but only 'wetting' the puck) and to my opinion these taste notably different that a regular shot. Perhaps I should let my wife do a blind tasting to check if I'n not too biased...

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mrgnomer
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#10: Post by mrgnomer »

Apart from putting in a silicone grouphead gasket and an IMS 200 RNT shower screen I've left my plumbed in Strega Top stock. I wanted to try a possibly more precise showerscreen with holes right to the center to see if it gives more even shower flow. It absolutely does when flushing. The extractions are good with it, I'd say better than the stock screen but it's hard to say. The stock screen wasn't in for very long and I when changed over to RNT from another precision shower screen I had time to get to know the Strega.

Flush rebound temp surfing, line pressure preinfusion, pump preinfusion/extraction, spring extraction...there's so many variables to experiment with. I stuck a Joe Frex timer on to time flush rebounds and preinfusions. Line pressure preinfusion I do by pulling the lever down enough to fill the group but not trip the pump and hold for a short time or until drips start appearing. I use an extraction mirror with an open portafilter watch for first signs and saturation evenness. Then I either push the extraction with a pump charge, mostly on light roasts, or just let the lever go and let the spring do a lower pressure ramp down extraction, mostly with dark classic roasts. Holding back the lever rebound, doing Fellini moves...more variables. Great machine, well engineered IMHO.

P.S. : with the silicone 8mm gasket the open portafilter doesn't lock in all the way and likes to creep off. I've come to understand the Strega uses a 7.5mm grouphead gasket. I haven't gotten round to sanding down the 8mm but will next time I lube the piston gaskets. Portafilter sneeze off explosions aren't fun.
Kirk
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