michael_pl wrote:Any thought to a pressure gauge so you have an idea of what flow you're delivering? I imagine it would be tough to be repetitive without an indexed zero position and measured flow for each "click" or rotation away from zero.
The panel pressure gauge is after the needle valve but before the gicleur. Because there is no pressure downstream of the gicleur without a portafilter, the panel gauge displays a pressure that is representative of the flow rate through the gicleur. If there is a specific flow rate that you would like to use to start your shots, simple adjust the needle valve as you would a Slayer (say 40g output in 30s) and note the pressure on the panel gauge. Let's say the gauge reads 0.5 bar once you get this flow rate dialed in. Now all you do is set the panel gauge to 0.5 bar during a quick flush before you lock in the portafilter. All your shots will then begin with exactly the same flow rate. From there, you drive the shot based on the panel pressure gauge, which shows you the maximum possible brew pressure and the flow into the cup. At the dwell point, where outside is high, but flow is very low, the panel pressure is very nearly the brew pressure. No flow, no pressure drop from the gauge to the group. Once flow starts picking up, you can either continue to adjust pressure, or you can focus on the flow. Either route you choose, the actual valve position is immaterial. All that matters is whether you need now flow or less to maintain the pressure or flow that you desire. Just remember that while you can control pressure or flow at will, you can't control both...
TomC wrote:Am I correct that this in its current configuration is still fully manual?
This is fully manual just like Bianca or any other FCD equipped E61, Slayer mod BDB, my GS/3, etc...
TomC wrote:Is there enough space inside to add both on the LMLM? I haven't followed too closely all the developments of the LMLM as far as the newer shot timers and controllers available in the aftermarket, but it would be a compelling setup if both would be available for it.
There is room enough for a ShurShot and corresponding plumbing.
That said, I am not at all convinced that a fixed timer
coupled with an instantaneous switch from low flow to high flow would be an improvement. The biggest determining factor I have found for how a shot will progress given a reasonably correct grind and dose for a given bean is the rate of rise from preinfusion to brew pressure. With this mod, you have full control and can slam the puck by going wide open to get a tighter shot with tons of dwell time or you can gently approach your target brew pressure for a softer shot that tends to flow faster and more consistently throughout. I'd hate to be tied to just one profile by putting a solenoid into this, buying you could stay in pre-brew with full manual control or swing full left for a timed step change from low flow to high flow, I'd consider that a pretty cool feature.
joey22 wrote:One question for you, it's cool to see how fast the brew gage responds to the needle valve adjustments. When you run it wide open does the brew gage match what is was before it mod (i.e. if it was set to 9 bar before does it still show 9 bar now with the needle open) or did you have to adjust the pump following the install of the mod?
It will not match at free flow unless you adjust the pump to compensate, but this would result in a higher potential max brew pressure. I tried this for a while on my GS/3 with the pump bypass set to 10.5 bar with the blind filter. This allowed me to hit 9 bar 9n the panel gauge within a turn or so from fully closed, but I quickly realized that I never set the needle there and the potential to overshoot my target brew pressure was not worth the increased flow rate range. I also never used that range, so why make things more difficult in the name of unused "flexibility"? It wasn't worth it for me, but others might find the tradeoff worthwhile.
I recommend always giving the peak brew pressure a "soft landing" when profiling a shot. What I mean by this is that when you crank the flow up, the pressure will climb slowly at first and then spike up when the puck compresses; it is a sound practice to "soften" the final spike in pressure by decreasing the flow so that the peak pressure is slightly less than what the pump would otherwise deliver on its own. This ensures that you are in control of the brew pressure, and not the bypass/OPV valve. Why does that matter? If the bypass valve is in control, the pressure/flow through the puck may not respond as quickly to changes made to the needle valve. When the needle valve is in control, you can precisely impact the brew pressure at any point throughout the shot.