I've got a new Vibiemme Domobar Super Electronic and Mazzer Mini and I'm trying to both understand some things that may border on being too detailed as well as fine tune my set up. Although I'm an aggressive espresso drinker (10 to 15 per day), I'm new to grinding, and to a HX machine. For the past 10 years, I've been pulling shots with a FrancisFrancis X1 using pre ground Illy beans. Although I have some Intelligentsia on order, I'm using Lavazza Super Creme (coming from Italy...probably not the freshest beans) right now and compared to my preground Illy, it's a world of improvement.

Heres where I am right now...I've got a grind that consistently gives me a single shot in 25 to 30 seconds with great reddish brown creme. I'm dosing my grind into my single filter bowl PF to where it's just level out of the doser and running my finger across the top to smooth out any slight overfill/lumps, then I'm tamping as has been described in great detail on this website. However, when I pull my shot, I'm usually at about 11 to 12 bars of pressure instead of the seemingly ideal 9 bars. What should I mess with to get my shot pull down to 9 bars, or am I being to picky and 11 to 12 bars is fine? Before anyone ask if I'm happy with the taste of my current shot, the answer is YES! I love it...it's heaven sent. But how will I know if it could be even better if everything was actually perfect?

Thanks,

Grey

The thread Dialing in a new espresso machine, a step by step guide may be helpful.

The OPV reads higher than the pressure on the puck. I adjusted my Vibiemme Levetta by taste and found 9.75bar on the panel gauge to produce an excellent double. I later measured the puck pressure at 8.22bar, very close to ideal.

There is a flow restrictor in the group that prevents the panel gauge from showing the true puck pressure. To get 9bar on the panel gauge, the water pours through the puck and makes a very bad shot.

If you have a blank basket, adjust the OPV valve down to about 9.75 bar. That will give you about 8.25 on the puck. Adjust the dose and grind so you get 30ml in about 30-35 seconds from when you hit the switch.

One caveat, your gauge may not read the same as mine, so don't be afraid to adjust the OPV if you don't care for the shot at 9.75 blind pressure.

To adjust the OPV, remove the 6 screws holding the body on and remove it. behind the machine, under the water reservoir is a large cut out. Inside that cutout is a large fitting with a slotted screw face. Turn it to the left to adjust down, right to adjust up.



Set the OPV for 9.5 bar, or close to it with a blind basket. when using coffee, the pressure will be in the 9 bar range then tweak to taste.

cafeIKE wrote:I later measured the puck pressure at 8.22bar, very close to ideal.

I know David Schomer says 8.2 bar is ideal for his blend, but I don't adhere to such absolutes for all blends. For example, Counter Culture recommends 9.5 bar for their Toscano blend. You may find lower pressures provoke less troublesome extractions while you learn the machine, then later decide 1.0 to 1.5 bar more increases the body or alters the flavor profile in a pleasing way.

Can any of you who make these very detailed adjustments give your opinion as to what 11 vs 9 bars of pressure would most likely effect in a shot...stronger more robust flavor, more bitter, burned flavors, very little to no difference, etc...

Thanks,

Grey

9 vs 11 bar is not a small adjustment. That is something on the order of 29psi. As a general guide, the lower pressure will produce a less harsh cup, softer more mellow flavors. Again that is a gross generalization. Extractions also tend to be cleaner at lower pressures. At 11 bar, if there is a defect of any type in your distribution and tamp, the water will find it and reward you with some massive channeling.

My personal preference, I run 9 bar. That gives me a nice balance between the body and flavor of the espresso. As HB points out, some coffees work better at higher pressure and others at lower. Not being able to change my pressure on the fly, and never using the same blend back to back, I settled on a mid ground. If you stick with one coffee most of the time, then tweaking your pressure to suite that blend may be worth while. But for now, I would recommend you concentrate on learning to use the machine before you start making many adjustments. Once you can pull consistently good shots, then you can make one small change and observe its effect. Then readjust based on the results until you are satisfied with the cup.

cannonfodder wrote:But for now, I would recommend you concentrate on learning to use the machine before you start making many adjustments. Once you can pull consistently good shots, then you can make one small change and observe its effect. Then readjust based on the results until you are satisfied with the cup.

I'll agree with that statement.... but after you move closer to 9 bar and away from 11 bar (at the puck). You may need to measure the pressure at the basket and not rely on the panel gauge via a pressure gauge installed on the portafilter. Once you dial it down, leave it alone as you learn.

There are enough other variables to play with. BTW, IMO the barista's consistency is by far the biggest variable when you get started.

HB wrote:

cafeIKE wrote:I later measured the puck pressure at 8.22bar, very close to ideal.

I know David Schomer says 8.2 bar is ideal for his blend, but I don't adhere to such absolutes for all blends.

I plead ignorance on the Schomer coincidence. The "8.22bar, very close to ideal" reference is to the generally accepted 8-9bar range for brewing espresso. Apologies for for not adding after the decimal places. I'll endeavor to be ever more pedantic.

HB wrote: For example, Counter Culture recommends 9.5 bar for their Toscano blend.

@ 180° @ 210° Single/Double 14/18/25 grams 5/10/20/50# tamp Macap/Mazzer/Swift/Compak Change one, change all.
IMO, the only consistent in espresso is there is none. It's patently ludicrous for anyone to recommend a single "best at" parameter.

HB wrote:You may find lower pressures provoke less troublesome extractions while you learn the machine, then later decide 1.0 to 1.5 bar more increases the body or alters the flavor profile in a pleasing way.

My recommendation for OPV adjustment, with caveat, is for a fundamentally identical machine upon which, after close to a thousand shots, I've found the recommended value to provide a pleasing balance over a wide range of coffees, both home and professionally roasted.

MY blend, MY roaster, MY profile, on days 4-7, MY grinder, MY 14.2±0.3g ±0.1g ±1 digit error dose, MY basket, NO WDT, MY 10# tamp, MY Vibiemme, MY puck temperature of ~198°F, MY puck pressure ~8.5bar, MY altitude of ~1050ft produces consistent shots that start evenly across the basket, tiger stripe nicely and deliver ~60ml in ~25 seconds after the first drop. REPEATEDLY. By all accounts, favorably regarded. YMMV. (Surely, this is understood and does not require adding as a disclaimer.)

As mentioned elsewhere, TASTE is the only arbiter. ALL measurements are made after an iterative process of honing the TASTE ALONE. Pull out the toys every so often as an insanity check to ensure no drift toward the center of the curve.

If I try a pound of a commercial roast, I'm thrilled if I'm pulling great shots before half is gone: 50g for the grinder, 50g for dose, 50g for temperature and maybe 50 to 100g for OPV, should I decide it needs adjustment. Once a chap who was having 'issues' with his machine dropped by with a quantity of well regarded coffee I'd never tried. I pulled a double into two cups. I sank mine and he exclaimed "What are you doing?!?!? This is great!" No, this sucks. Wait. 4 or 5 sinkos later, explaining what I was doing AND WHY, I gave him another. "Wow! NOW I get it!"

Rule 1 : If it tastes like sh!t, it is. Make ONE change to drive the taste in the opposite direction.