Is it really necessary to adjust vibe pump brew pressure? - Page 2

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cannonfodder
Team HB

#11: Post by cannonfodder »

I will chime in at this point, since that Scace 2 is sitting beside my Elektra and the Domobar Super. I made a portafilter pressure gauge some time ago, the gauge on the Scace and the one on my PF are very, very close.

The pressure on my Elektra A3, which uses a rotary pump plumbed into a regulated mains, I get 130psi dead-head (home made PF gauge) and 131 on the Scace with flow. That could simply be the tolerance in the gauges. The onboard gauge reads around 9.2 bar.

On the VBM (vibratory pump), I have the pressure set dead-head at around 128psi (gauge is on loan so I can not check this moment) but the onboard gauge reads 9.6 bar. I get 9.4 onboard and 120psi on the Scace.

My Isomac is around the same. When I set my OPV, I go .5 bar higher than my target temperature, on a rotary I set it exactly where I want it. Also, remember most vibratory pumps have a pronounced drop in pressure when the heating element engages while the pump is running.
Dave Stephens

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Ozark_61 (original poster)

#12: Post by Ozark_61 (original poster) »

HB wrote:FWIW, Chris' Coffee technicians adjust their outgoing espresso machine brew pressure to 10 bar no flow. But for the barista who cannot have enough tools, there's the new Scace II themofilter:
Good enough for me. I'll do the same and see how the backflow amount into the reservoir changes with the change. It's interesting, however, that many machines from Italy seem to be set to the higher pressure at default. I don't think it's a mistake - yet many find an improvement in their shots with a lower pressure. Time for a scotch.

Geoff

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another_jim
Team HB

#13: Post by another_jim »

I have a skewed perspective on this.

My Tea was delivered set to the standard 11 bar, and ran around 10 for singles and ristrettos. When I adjusted it down to run between 8 and 9 for all shots, it made a big difference. The taste was more consistent and better for the short shots. Ken had much the same experience when he adjusted his vibe Cimbali, so much so, that he now thinks buying the rotary version was not a cost effective decision.

The Elektra has no stock OPV at all, and runs at god only knows what pressure when making shots (probably around 10 to 12 bar depending on volume). I installed an OPV, and it made zero difference on the taste. I still have no clue why this is; but I did take the OPV back out. This was a real dumb move in theory, but it has not made a whit of difference to the shot quality, and because the way the machine works, it reduced the noise a lot.

My advice is to clear away your preconceptions, and just do the tasting, when doing adjustments on whatever machine you have.
Jim Schulman

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TimEggers

#14: Post by TimEggers »

another_jim wrote:The Elektra has no stock OPV at all, and runs at god only knows what pressure when making shots (probably around 10 to 12 bar depending on volume). I installed an OPV, and it made zero difference on the taste. I still have no clue why this is; but I did take the OPV back out. This was a real dumb move in theory, but it has not made a whit of difference to the shot quality, and because the way the machine works, it reduced the noise a lot.

My advice is to clear away your preconceptions, and just do the tasting, when doing adjustments on whatever machine you have.
Most interesting! I agree the gage is really pointless. I used to be hung up on it, but at the gages 9 bar my espresso was too harsh and just unpleasant. I slowly dialed it down over the course of a few days. Once the gage got down to 8 bar (again what the pressure at the puck is I have no idea) the espresso became balanced and delicious. Yet another follow your tongue escapade.
Tim Eggers
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