Paolo_Cortese it can lower not increase, the max pressure it’s always almost 10,5 bars. Surely Dave can explaim much better the advantages.
When the system has air above the water but below the piston some spring movement is used to compress the air, this limits the maximum pressure it can develop as some decompression of the spring has already happened.
The design of the all the LSM groups (because of the past and positioning of the inlet holes), does not open the water inlet valve until 20-30% of the piston movement (approx), has already happened. So air is above the water. Hence the pressure can be around 9.5 to 10 bar. If you can open that valve almost immediately the piston moves, you will get just up to 11.5 bar .
So of course, if you can vary when that valve opens by sliding the piece up and down on the flush lever…you have some control of the maximum pressure in the system. from around 9.5 to 11.5 bar…and of course increase the swept volume greatly for high brew ratio shots (whilst maintaining good pressures).
With the safety sleeve, you should be able to get a slightly wider range of pressure from 9 to 11.5 bar. It has a second use with the safety sleeve, it allows you to set up a walk up and pull pressure rather than always having to pre-charge to avoid a 9 bar maximum
The reason for 2 handles is if ever the lever assistance system is put in, the flush lever would be used to invoke it and people are right/left handed. It also means when flushing, you can do it with either hand.
LMSC The only benefit I see is flushing after the shot in my case than pulling the lever down to flush. I do not see any additional benefits this during the PI. I am not keen to inject any air into the chamber during PI, however small it might be. :-)
But you always are…that’s the point of this system. You can also retrofit to your machine, no problem.