samuellaw178 wrote: I'm almost sure of this (based on my previous experience with Rossa and currently with Forge) - if you allow hot water to sit on top of coffee with no pressure (allowing water to seep/diffuse into coffee), and then increase the pressure veeerrryy slowly (ramp), you can achieve similar effect of Slayer shot.

Just did this on the Forge. 10 notches finer from my usual grind setting on a HG-1 2014. 0 bar preinfuse for 15 sec and then start pressing geeennntly. Results? Almost a gusher at 4 bar. That'd have been a choke using the usual method.

For second trial, I went even more adventurous and tightened up another 5 notches - so 15 notches finer (translate to vertical burrs movement of 0.2mm) from my usual setting. Same procedure as before and got a good flow at 8-9 bar. The shot tastes significantly different and is sweet (maybe a tad overextracted too), but not something I'd like for often.

nickw wrote:
I've played with this on my L1 (by holding right at the point where the water slowly fills the group - as mentioned in the post above). I also found you needed to tamp harder, or the slow water flow would carve holes in the puck (at least on the L1).

I will try this on the lever tomorrow as it's turned off at the moment. But I reckon it'd be possible but tricky as you have experienced.

samuellaw178 wrote:Just did this on the Forge. 10 notches finer from my usual grind setting on a HG-1 2014. 0 bar preinfuse for 15 sec and then start pressing geeennntly. Results? Almost a gusher at 4 bar. That'd have been a choke using the usual method.

For second trial, I went even more adventurous and tightened up another 5 notches - so 15 notches finer (translate to vertical burrs movement of 0.2mm) from my usual setting. Same procedure as before and got a good flow at 8-9 bar. The shot tastes significantly different and is sweet (maybe a tad overextracted too), but not something I'd like for often.

I'd be interested to hear the results would be with your Mythos (taste wise).

samuellaw178 wrote:I will try this on the lever tomorrow as it's turned off at the moment. But I reckon it'd be possible but tricky as you have experienced.

Curious to hear how it goes for you.
Perhaps if I went even slower I wouldn't have the problem? The group would fill in the 8-12 second range (on average). I found it difficult to modulate the flow rate.

nickw wrote:I'd be interested to hear the results would be with your Mythos (taste wise).

Curious to hear how it goes for you.
Perhaps if I went even slower I wouldn't have the problem? The group would fill in the 8-12 second range (on average). I found it difficult to modulate the flow rate.

Can't stand the suspense and warmed up the lever anyway. Tried it and it worked. Sort of anyway, as I don't feel it's repeatable/controllable enough. The brew pressure is in the dark and the spring/line pressure are causing a disconnection between the tactile feedback and actual pressure. But I did manage to pull a shot that would've choked (10 notches finer). To confirm, it did choke using the standard 10 sec preinfusion and release method.

I should've updated my equipment list. The Mythos was gone last week. The HG-1 gets the love mostly and the Mythos was just gathering dust (only because it's not that suited for single dosing)

nickw wrote:
Same deal on a Strega. You can toggle the pump on/off (a dimmer mod would make things much easier and more repeatable). Although running PI times of 20-30 seconds water temp comes into play. You would want to bump up water temp
.

Wouldn't the thermostatically controlled heaters in the group head on the Strega prevent the water temperature from cooling?

nickw wrote:Sounds interesting. I would be interested to know how slow it can go? The valve would offer repeatability and consistency.

I've played with this on my L1 (by holding right at the point where the water slowly fills the group - as mentioned in the post above). I also found you needed to tamp harder, or the slow water flow would carve holes in the puck (at least on the L1).

As luck would have it, I start talking about the group and it showed up in the mail today. Sorry about the cluttered desk and poor light, but hopefully you can see the back screw. One with it all the way in, and all the way out. I have a hard time finding real specs for the group, so I'm not sure the rated flow for each setting, but it is something I'm planning on finding out. I need to also figure out the connection size on the back of the group.

Most of my other parts arrive next week, so hoping by that weekend I'll have some basic tests going.

On my Sorrento that threaded screw is set so that the 4th raised thread from the top is flush with the top of the raised valve body. Roberta Bosco told me that it is only used to shut off the water flow when you want to service one group without taking a multigroup machine out of service. She didn't feel that playing with different settings would have much effect on the shot. It will be interesting to hear what you find.

JohnB. wrote:On my Sorrento that threaded screw is set so that the 4th raised thread from the top is flush with the top of the raised valve body. Roberta Bosco told me that it is only used to shut off the water flow when you want to service one group without taking a multigroup machine out of service. She didn't feel that playing with different settings would have much effect on the shot. It will be interesting to hear what you find.

bm_cricket wrote:This diagram shows the part necessary as "W.10374" but what they send you is "BF.165". The part I circled is what we you want if you plan to use "AS.90" to press down on "AS.61" and use it as an adjustable retention valve.

This quote is from the Open Source Lever thread, again not too sure how adjustable it is, but if it can be in fact totally closed when all the way down, I bet you could crack it 1/2 to 1 full turn and get a very restricted flow. Once I can find the thread specs or figure them out and connect it to my line pressure I'll do some measurements.

I know we've been going off on flow restricting/profiling topic, but I think they are inter-related enough to make sense in this thread.

samuellaw178 wrote:Can't stand the suspense and warmed up the lever anyway. Tried it and it worked. Sort of anyway, as I don't feel it's repeatable/controllable enough. The brew pressure is in the dark and the spring/line pressure are causing a disconnection between the tactile feedback and actual pressure. But I did manage to pull a shot that would've choked (10 notches finer). To confirm, it did choke using the standard 10 sec preinfusion and release method.

I should've updated my equipment list. The Mythos was gone last week. The HG-1 gets the love mostly and the Mythos was just gathering dust (only because it's not that suited for single dosing)

If the theory of why you can grind so fine on a Slayer is simply that the puck is slowly wet at hot water at "gravity pressure" (like an EspressoForge) then I suppose you could prewet the puck with kettle water or hot water spout water right before lock in and achieve the same effect.

dominico wrote:If the theory of why you can grind so fine on a Slayer is simply that the puck is slowly wet at hot water at "gravity pressure" (like an EspressoForge) then I suppose you could prewet the puck with kettle water or hot water spout water right before lock in and achieve the same effect.

I had remembered a thread about something like that, then realized when I found it that you posted it!
Pre-wetting / pre-blooming the puck before extraction

Though I haven't done much for experimentation there on my BDB. Would like to try it out on my new upcoming lever once everything else is in place.

I'm guessing that the reduced flow rate is pretty much just that...keeping the cylinder or puck at lower gravity pressure for some longer amount of time than would be normal. Once the cylinder or hydraulic system after any restrictor fills, then pressure starts building. I think many other pump machines have 0.5mm to 1mm jets to achieve a similar (but not adjustable) effect.

JohnB. wrote:On my Sorrento that threaded screw is set so that the 4th raised thread from the top is flush with the top of the raised valve body. Roberta Bosco told me that it is only used to shut off the water flow when you want to service one group without taking a multigroup machine out of service. She didn't feel that playing with different settings would have much effect on the shot. It will be interesting to hear what you find.

I just pressure tested my group today, but don't have the right fitting, and it's not fully connected to a frame yet. Once I can get those sorted I can do at least some cold tests with the valve and see what kind of flow rates I can get.

EspressoForge wrote:I'm guessing that the reduced flow rate is pretty much just that...keeping the cylinder or puck at lower gravity pressure for some longer amount of time than would be normal. Once the cylinder or hydraulic system after any restrictor fills, then pressure starts building. I think many other pump machines have 0.5mm to 1mm jets to achieve a similar (but not adjustable) effect.

That's how it works on the Speedster/Spirit. Kees moved the .6mm jet from the group into the hx to brew boiler feed pipe at the rear of the machine to slow the ramp to pressure. When you engage the manual PI it takes a full 12 seconds for the pressure to build to 3 bar at the puck. Initial wetting of the puck is at almost zero pressure and it slowly increases as the pipe & PI chamber fill with water after the jet.