La Marzocco Linea Mini Flow Control Mod - Page 2

Need help with equipment usage or want to share your latest discovery?
joey22

#11: Post by joey22 »

cf wrote: When running with no resistance or portafilter, the pressure gauge tops out a little over 6 bars. I think previously it went full 9 bars with no load, not sure. I haven't measured the grams/sec to see what kinda flow that is wide open. With coffee, the gauge does slowly ramp up to 9 bars as the headspace above the puck gets filled with water regardless of how low a flow I have, it will happen eventually.
Interesting that seems odd to me, I would have expected the reading on the brew gage with the needle valve wide open would be essentially unchanged from the pre-mod reading with maybe a minor drop in pressure to account for losses through the needle valve assembly. Unless you had previously changed your pump pressure on the back of the machine I'd have to assume it was set at 9 bar from the factory.

PS are those the LM walnut paddle and knobs? they look sharp on the white Mini!

cf (original poster)
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#12: Post by cf (original poster) » replying to joey22 »

Yes to be honest, before I did the mod I did adjust the pressure down to 6 bar per LM's recommendation to fiddle with light roasts, but I turned it back to 9 bar as far as I can tell before I completed the mod. I might not have perfectly adjusted it because I think I would need a scace to determine pressure at the brew group. But good point, I could try to crank it back up on the pump to see if at free flow it hits 9 bar. I'm getting good shots regardless though.

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joey22

#13: Post by joey22 »

Thanks for the update. I also tried the 6 bar adjustment for few months after speaking with LM about changing to the 0.6 mm flow restrictor/gigleur. I did find lighter roasts a bit easier to work with and noticed the overall flow rate reduction, but found too much of a compromise on body with a more typical espresso roast. I'm back at 8.5 bar now and finding it to be sweet spot.

I'm not sure if this still current, but I did see a rental option for a scace device through Caffewerks:
https://caffewerks.com/products/scace-d ... ZYQAvD_BwE

I have no idea if rental is currently being offered, but it could be an option for getting a better understanding of pressure at the brew head if you don't have access to a scace otherwise.

cf (original poster)
Supporter ♡

#14: Post by cf (original poster) » replying to joey22 »

Awesome, thanks for the link! And thanks for sharing your experience with the 6 bar adjustment. I didn't pull enough shots at that pressure to get a good feel before adjusting it back up. But I do think the best shots I had from the stock Mini were classic espresso roasts with really creamy body with chocolate and caramel notes at the 9 bar setting. Really good.

Legend_217

#15: Post by Legend_217 »

$5,400 for a machine without shot timer and flow control ? You guys overpaid by $3,000 just for the brand

blondica73
Supporter ❤

#16: Post by blondica73 » replying to Legend_217 »

Please refrain from making negative comments in this thread as this thread is about flow control mod on Linea Mini. The price to feature issue has been addressed in other threads.

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Jake_G
Team HB

#17: Post by Jake_G »

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.
Michael,
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?
Tom,

This is fully manual just like Bianca or any other FCD equipped E61, Slayer mod BDB, my GS/3, etc...

The
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.

Cheers!

- Jake
LMWDP #704

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michael_pl

#18: Post by michael_pl »

Jake_G wrote:Michael,
The panel pressure gauge i......l, you can't control both...

Cheers!

- Jake

Thanks for the detailed response - looks good! Hope it's working well for you!

DaveB

#19: Post by DaveB »

Jake_G wrote: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.
I just used this technique to good effect; only difference is that I let the pressure ramp up on its own and then stopped the pressure rise at 8 bar and let the rest of the shot proceed on its own as the pressure slowly declined.

Here's my humble example.

Thanks again, Jake for the inspiration!
Von meinem iPhone gesendet

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Jake_G
Team HB

#20: Post by Jake_G » replying to DaveB »

That shot looks beautiful.

I often let the pressure decay naturally, but typically close the valve for the last few grams, as this seems to stave off any bitterness in the final drops. I also tend to ramp up before the pressure would rise on it's own as this allows for more time of the shot to be spent flowing compared to soaking (preinfusion, pre-brew, whatever term you like) and generally results in better body and less astringency with a more coarse grind than what "riding the ramp" will allow.

Cheers!

- Jake
LMWDP #704