Espresso shot parameters not quite right, help?

Tips and Tricks you have discovered with your S1, VII, Mini-VII, Dream, or Dream T that lets you do any aspect of coffee making, steaming, maintenance, etc better.
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Owen
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Espresso shot parameters not quite right, help?

Post by Owen »

Hey ladies and gents, I am a long time reader but first time poster and had a question that one of you may be able to help with. I am the new owner of a Dream T (previously came from a Breville Oracle), and can't get my shot parameters to make sense. I am still dialing in, but here's what I have so far:
While using the Spaz double basket, my shots either come out on time and under pressured (the manometer never reads more than 7.5 Bar....on the blue / green edge, or they come out over-time (burnt and over-extracted appearance) but have the manometer approach 9 Bar (closer to 8 most of the time). The perplexing part is I use the same dose, the same calibrated tamper, but only change the grind. As I grind finer, I approach the 9 bar, but never hit it, and have a break-apart mini mouse tail stream, and a way over-extracted appearance and timed shot. When I grind more course, the 2 ounce shot comes out at about 30s, and appears correct, but the pump never hits the 9 bar (mostly on the blue / green edge line). As a side detail, when I back flush, the manometer reads a steady 9 Bar at about 9-10s on the shot timer.
What are some of your expert ideas, and thanks in advance?
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chas
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Re: Espresso shot parameters not quite right, help?

Post by chas »

I think it's just a matter of adjusting the pump pressure up. The pressure is measured close to the output of the pump. The restriction of the plumbing between the pump and the group drops the pressure. I have found that in order to get a true 9 bar at the group you need to see 10-10.5bar when using the blind basket used for backflushing.

I have a Scace Gen 2 device I use with my machine. It actually lets 2 oz of water shoot out the bottom in a little over 25 seconds. When I use the Scace to set the group pressure to 9 bar, then use a blind basket, I see 10.5 bar.
Chas
LM GS/3 & LaSpaziale Dream v 1.25 (US 120V)
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Owen
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Re: Espresso shot parameters not quite right, help?

Post by Owen »

Thanks Chas, it's a new machine so I haven't tinkered with it yet, but will give this a try. Once I get 10 -10.5 bar using the blind disk, I'll rework my grind and see if I can't make it look right and report back. I appreciate the help.
Owen
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Re: Espresso shot parameters not quite right, help?

Post by Owen »

Chas,
Thanks for the suggestion. I saw the owner's manual outlines it pretty well on page 19....I swear I read it cover to cover before my machine came so I'd be ready to hit the ground running, but without having the machine to play with along side the reading some of it didn't stick. Anyway, gonna dive back into the manual today and see what other Easter eggs I can find.
Results: I set the pump to 10.5 bar with a blind disk, fined up the grind just a slight bit, and out came a 9 bar shot!

Cheers
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chas
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Re: Espresso shot parameters not quite right, help?

Post by chas »

Here's a related thing to keep in mind for the future. The rotary pump just adds pressure to the incoming line pressure. For example, if you have 3 bars of pressure coming into your house and you adjust the pressure to 9bar, it gets there because the pump is boosting the pressure by 6 bar adding to the incoming 3 bar of pressure.

The downside of this is that if your house water pressure is not steady you may find it necessary to readjust the pump pressure periodically. However, the pumps are pretty stable. There is usually little to no variation in the pump's pressure output unless they completely fail.
Chas
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Re: Espresso shot parameters not quite right, help?

Post by mmg »

Is the 10.5 bar setting valid on all machines? I was quite satisfied when I saw mine hitting 9 bar steadily, but I'm now rethinking this.
Is the gauge just not well printed or is it reading a wrong pressure? That is to say a portafilter gauge would read differently?
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chas
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Re: Espresso shot parameters not quite right, help?

Post by chas »

With a blind basket, the pressure is the same everywhere from the pump to the group since there is no water flow. However, with water actually flowing through the group there is a pressure drop between what you see on the gauge and what you actually get out of the portafilter. I have found empirically that if you set the pressure between 10-10.5bar using a blind basket and the built-in gauge you actually get ~9bar when water is flowing through the coffee bed of the portafilter such that you get 2oz in 25-30sec.
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Re: Espresso shot parameters not quite right, help?

Post by mmg »

When you say ~9 bar when water is flowing through, do you mean as seen on the internal gauge?
So the discrepancy would only be between the blind basket and the actual espresso, not between the internal gauge and the real pressure?
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chas
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Re: Espresso shot parameters not quite right, help?

Post by chas »

Sorry, you only see 9bar if you use a portafilter pressure gauge with water flowing through it. Since the built-in gauge picks off right by the pump output you actually see the pump output pressure on the built-in guage and NOT the pressure seen by the coffee grounds.

To build your own, you need an external gauge from expresso parts that screws onto a PF where the spout normally screws on. Then you buy a T connector at the hardware store that screws onto the bottom of the PF. Then you screw the pressure gauge to one of the Tees and put a needle valve on the other tee with some copper tubing or similar fitting that aims the water down into the drip tray. Once you set the needle valve so that 2oz of water comes out in whatever time frame you desire - usually 25-35seconds, you are ready to adjust your pump pressure.

BTW: If you build the PF pressure gauge with the needle valve then turn the valve off so that no water flows, you will see that the built-in gauge and the PF pressure gauge read the same.

It looks like the best deal at the moment is on eBay: https://www.ebay.com/itm/131182781205?c ... I0QAvD_BwE
Chas
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Re: Espresso shot parameters not quite right, help?

Post by mmg »

That is very interesting, more or less what I expected from intuition, not entirely what I usually read online. I may get a gauge down the line, for now I will try to set it to 10.5 bar and check the result.
I had always felt like the pressure was not exactly what I wanted, now maybe I wasn't totally wrong.
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