Owner experience with Bezzera Strega - Page 135

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#1341: Post by baldheadracing »

Your machine is operating normally in my eyes.

What people do is lift the lever a bit to stop the pump.

For example, once the group is (almost) full of water the pump's noise will slightly change. This happens just before the OPV opens. As soon as you hear that change in noise, carefully lift the lever just enough to turn off the pump and carefully (use both hands) hold the lever in that position. Once you see a drop, then release the lever carefully - using both hands.

You can further control pre-infusion pressure by lifting the lever (just enough to turn off the pump and holding the lever there until drips) earlier in the process, e.g., based on pump noise in your video, somewhere in between 1:28 - 1:33 in your video. The lever will grab in different positions depending on when you lift as a result. I would typically lift at about 1:31.

In a nutshell, the Strega is an instrument. You control the temperature with flushing and the pressure with the lever. Just like a musical instrument, there's a learning curve before the instrument - and the espresso - sings.

Good luck!

ETA: For example, this morning I was pulling a very light roast. To get a high extraction temperature, I did not flush the group before pulling. (I typically only flush the group for traditional Italian-style blends, but that's my taste.) To get a low pre-infusion pressure, I lifted the lever to turn off the pump just as the pump noise started to change. (Again, my preference. Someone else might prefer the taste arising from letting the pump pre-infuse longer, and thus leading to a higher pressure.)

ETA2: Have you seen the three videos in this thread? Bezzera Strega - The Movie


#1342: Post by teh » replying to baldheadracing »

thanks for your lengthy reply. That gives me a bit more peace of mind.

Thank also for the time of the change in my video. The change of pump noise is not as apparent as I believed it would be. I might experiment with lifting the lever slightly earlier.

I know that getting to a real good espresso might take some time. I think puck prep is where I need to learn the most. Milk drinks turn out great already but the espresso will need more training on my end I think.

I have watched those videos and Jim's videos were actually what made me chose the Strega in the end.

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#1343: Post by baldheadracing » replying to teh »

Perhaps start by lifting the lever once the OPV opens - as once the OPV opens there is no more need for the pump to be on (more-or-less). That should also help develop your sense of the pump noise.

I actually have a pressure gauge on my Strega to determine pre-infusion pressure. However, opening the machine voids the warranty (in Canada), so I didn't install the gauge until the warranty period was over. I've found that there are three different pre-infusion pressures that I regularly use:
1. low pressure = just before the pump noise changes; this emulates a dipper-fed group - roughly 1.25 bar;
2. max pressure = just before the OPV opens - roughly 9 bar; and
3. mid-pressure = in between 1 and 2; which emulates a line-fed group - roughly 3 bar.

For quickly improving puck prep, opinions vary, but I would recommend three things:
1. a bottomless portafilter for obtaining feedback on how your puck prep is progressing;
2. a distribution tool which can be anything from a few paperclips twisted together to this design: https://levercraftcoffee.com/products/l ... ion-tool-1
3. a funnel to contain the grounds while grinding and distributing, which can be anything from a cut-up food container (e.g., single-serve yogurt container) to Tidaka's tamp-through funnels: https://www.tidaka.net/de/trichter.html

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#1344: Post by TigerStripes »

Would it be possible to adjust the OPV to 3 bar? I've seen folks talking about a dimmer with this machine, but seems much simpler to unscrew the OPV spring a bit, or replace the spring altogether.

If OPV was set to 3 bar, the pump would stay on and you could pre-infuse as long as you wanted at 3 bar until you let the lever go up?

Is there something I'm not considering with that scenario?
LMWDP #715

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#1345: Post by baldheadracing » replying to TigerStripes »

It may be possible - I don't know if the Bezzera OPV will adjust that low - but if you're going to open up the case to that extent, then one might as well just add a pre-infusion pressure gauge and gain the additional flexibility of setting pre-infusion pressure to whatever you want. (There is already an open port on the Strega for a pre-infusion pressure gauge - located on the same fitting as the OPV.)

Also, unlike pump machines, the Strega's OPV dumps into the drip tray - so that water line should be re-routed to the reservoir unless the drain tray was plumbed in.

The dimmer mod sounds like a good idea until one measures the actual pre-infusion pressures. In the Strega, the dimmer doesn't accomplish anything in terms of pre-infusion pressure that can't be replicated by lifting the lever. In addition, changing the pump behaviour changes the temperature performance of the machine as the Strega is a cold-fed HX. The rate of feed into the HX is determined by the pump flow; unlike a single-boiler machine, a slower pump flow will lead to hotter brew water temperatures. (The Strega Top can be line-fed at a lower pressure, but unlike a line feed, flow and pressure are very correlated in a vibration pump.)

ETA: I did the dimmer mod on my Strega at the same time as I put in the pre-infusion pressure gauge. The dimmer is being removed the next time I move the machine.

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#1346: Post by TigerStripes »

Thanks Craig - that is helpful information. One thing I'm curious about your pre-infusion pressure gauge. Is it installed at the 4 way tee before the check valve? It looks like that setup gives you pre-infusion pressure info, but wouldn't give you pressure readings when you lift the lever, right?

I suppose the pressure curve isn't all that important once you lift the lever since it's always the same, but if you wanted to adjust pressure on the lever it would be nice to have a pressure gauge readout.

Has anyone figured out a way to get pressure readings while the spring raises? Do the HX tubes maintain high pressure as the lever raises, or is the entry to the group closed off by the piston when the lever is raising? Perhaps that is why the new ACM lever has the gauge mounted right on the front of the group.
LMWDP #715

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#1347: Post by baldheadracing »

You are right - the gauge does not show extraction pressure, and the gauge is installed at the four-way tee. As a result, the gauge doesn't show pre-infusion pressure if the OPV is triggered - the gauge shows the pressure before the OPV.

The HX circuit retains the last pre-infusion pressure for a while, but the pressure will dissipate over time.

There are essentially three ways to get extraction pressure:
- via a modified basket, e.g., Scace2
- via a hole in the side of the group like you mention; or
- via a hole in the piston & a hollow piston rod, e.g. pressure profiling kits for the Cremina, La Pavoni, etc.


#1348: Post by teh »

One more question:

I really enjoy the classic single shot espresso more than a double shot. Any one else doing single shots on their Strega and can recommend a good single basket? I was about to buy a VST 7g basket but saw a few people saying that those precision baskets and their need for finer grinds are not really well suited for the Strega.

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#1349: Post by baldheadracing »

I use the Tidaka.net set from Germany: https://www.tidaka.net/de/tamper/set-angebote.html

I have both a "regular" 7g basket (clone of La Marzocco L115A branded by LF) https://www.tidaka.net/de/siebe/1er-sie ... amper.html and the VST-7, which is similar to the La Marzocco X basket: https://www.tidaka.net/de/product.html? ... &info=1270

I haven't noticed a huge difference between the two baskets, but I haven't done a rigorous taste comparison. However, the "regular" 7g basket that I have from Tidaka does require a finer grind than the VST-7, which is the opposite of conventional wisdom. This could be just due to production variability.

I think that the comments on VST baskets needing finer grinds were aimed towards the VST double baskets, e.g., VST-15, in comparison to conventional double baskets like the one that comes with the Strega. Again, I haven't done a rigorous comparison.

I normally use the VST-7 and VST-15 in the Strega so I can use either basket and keep the same grind size and taste. However: I am controlling pressure with the Strega's pump; I usually pull quite light roasts (a.k.a. "cupping roasts") in the Strega; and I have been using VST baskets for years so I'm used to them.


#1350: Post by teh »

thanks for the reply. I will probably get a La Marzocco single basket and give it a try.