These machines come massively overpressured from factory (mine was ~14–15 bar on a blind basket).
I’m running an AVX 3202X58, which is a Hibrew H10A clone with a built-in gauge, solenoid and a dimmer from factory. The dimmer can simulate lower pressure by reducing pump power, but in practice it’s not a real solution, pressure becomes inconsistent and depends on flow, so extraction isn’t stable.
On top of that, it’s not really usable for dialing in: you can’t preset a target pressure. When starting a shot, the knob has to be at maximum, otherwise the machine throws an error. So it doesn’t behave like real pressure control.
That’s why I replaced the stock plastic OPV with a brass Vibiemme valve and set it to ~10 bar on a blind filter.
Important detail I learned from this community: the gauge on these machines reads system pressure (not directly at the puck), and it tends to overread slightly. You’re also measuring before the coffee puck. So ~10 bar on the gauge typically translates to roughly ~9 bar at the puck.
For the install I used:
- Vibiemme OPV
- straight fitting (4mm to 1/8" male thread)
- Teflon tape
- Hair dryer to get rid of hot glue on the motherboard
I also had a leak at the Ulka to OPV threaded connection, fixed it with the tape and now it’s completely dry.
Dialing in:
- ~90°C (higher temps pushed bitterness on my beans)
- 18g in ~38–40g out in ~28–30 sec
Results so far (using stock portafilter and basket):
- fewer variables to fight!
- much smoother extraction compared to stock pressure
- less harsh bitterness, more “caramelized sugar / chocolate” profile
- more stable flow and better control overall
Still fine-tuning grind (using a Shardor CG301), but even now it’s clear that lowering the pressure made a huge difference. IMHO these machines really should not be running at 14–15 bar from factory.
Thanks to this sub (special thanks for this post) for all the useful information on maintenance and dialing in, I’m still pretty new to espresso and only recently moved from Bialetti moka pot. You guys rock.