2 hours ago, The Systemic Kid said:
Have a look at the video below - you have probably already seen it. Am guessing Frans has got the PI set pretty high - at or around 6 bars given the pumps on both machines are kicking in repeatedly during pre-infusion. Don't think Frans is adjusting PI pressure during either shots. At lower PI setting, i.e. 3 bar, the pump does not kick in and out during pre-infusion. In the Decent video, guy makes reference, I think, to hitting the puck at 6 bar and then dropping it to 3 bar - this is during pre-infusion. I guess this is possible via using the app but I would wonder how accurate it is as there is no feedback (manometer) to let you know exactly what pressure is occurring at what stage during the extraction.
The Vostok looks as if it takes a different approach which won't be clear until the machines are out there in the hands of those who have experience of Londiniums. The double spring in the San Marco group used in the V will provide a different profile to the single spring on the Londinium which peaks at 8.5 bar when the lever is released. Am guessing that the the pressure declines quite rapidly during the extraction.
As DaveC has demonstrated, it's possible and appears quite easy to retard the spring induced pressure on the V by holding back the lever. The key is that you get feedback in real time thanks to the inclusion of the group head manometer.