To continue my point above - and I deciced to make this a new post - so that my italicized point above stands alone:

If I loaded a "Slayer grind" into my L1 it may never saturate. If it did, it would take a very long time, and the water would be too cold. If I tried to pull a shot before full saturation of the grounds, the machine would choke. It would micro channel and the shot would be horrible.

On a line level machine, you could try holding the lever around bite point, so that water very slowly fills the group (trying to emulate a Slayer's prebrew flow rate). And if you had your pressure regulator set around 4-5bar, you would eventually saturate the coffee, but much of the water would of cooled in that time. How much it cooled would depend on time and original water temp (of which, you could bump up boiler pressure/temp) if you always did this. Although repeatability would be difficult with this method.

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.

That's where the Slayer gives very easy and repeatable results.

But at this point I want to say:
The machines we're talking about in this thread are all good in their own right.
Having owned a Strega, L1 and now Slayer, I would say: upgrade your grinder first.
An e61 hx machine with a Terranova grinder will taste better than a Slayer with a generic mazzer/compak/etc.

Each machine has it's own pro's and con's. Imho:
Personal skills first
Coffee second
Grinder third
Machine fourth

If I was on a budget, I'd spend it on good coffee. I'd take whatever used reasonable espresso machine I could find at a good deal (lever or otherwise). I'd put my money into a grinder good (probably a used Versalab, then align it), then spend my time reading and practicing Would give you the most bang for your buck, imho.

nickw wrote: Thats where the slow flow rate of a Slayer, along with the slow rising pressure allows for both slow and full saturation. Thus a very fine grind.

* Max pressure achieved during PI depends on: pre-brew flow rate, set machine pressure, coffee used, your grinder, degree of fineness ground etc..

** Max pressure depends on lever type: Boiler level, or plumb-in/line-level.
Hybrids like the Strega are variable and can go higher. Toggling the pump on/off, or modding with a dimmer allows for a lot of flexibilty.

A Slayer uses an adjustable needle valve to slow the flow rate to the puck. Some lever groups have that integrated into the design, and some use a different external method. But this isn't exclusive to the Slayer, or even to a pressure profiling machine.

Strega may be capable to do a lot of variability, but without the dimmer mod, I don't think it's realistic. I tried counting seconds on my Strega but could never get repeatable results that I was happy with.

nickw wrote: If I loaded a "Slayer grind" into my L1 it may never saturate. If it did, it would take a very long time, and the water would be cold. If I tried to pull a shot before full saturation of the grounds, the machine would choke. It would micro channel and the shot would be horrible.

On a line level machine, you could try holding the lever around bite point, so that water very slowly fills the group (trying to emulate a slayer in slow flow rate). Say you have your pressure regulator around 4-5bar, you would eventually saturate the coffee, but the water would of cooled in that time. How much it cooled would depend on time and original water temp (note: you could bump up boiler pressure/temp) if always did this. Repeatability would also be harder here.

Try to lower your pressure regulator to 1-2 bar on the L1 and grind the same as your Slayer. I bet you can get a similar shot with some work, I don't think cooling is much of an issue, it would be the same on any machine with a similar flow rate (and amount of metal). The low initial flow of a Slayer helps to do about the same thing, but there are multiple ways of achieving the same result. At least this is all from my experience. It's hard to exactly compare machines because they are complex systems.

Good points Nick. There's certainly a difference between flow profiling vs pressure profiling. I don't think anyone here is illusioned into thinking they could reproduce Slayer style shots on a spring lever. Though, the later part of flow profiling is pretty similar to pressure profiling, which was the part of knowledge borrowed by Dominick from Slayer's manual. Pressure profiling can still allow you to go finer than usual but not as fine as flow profiling would.

nickw wrote:The slower you expose the puck to water, and the slower you saturate it, the finer you can go.

Also, I would like to 'dissect' the flow profiling on Slayer. In my opinion, the key to extremely fine grind (aka as in Slayer style shot) is not the flow rate itself. The flow rate is the indirect factor in determining the pressure ramp up. Faster flow rate = faster ramp up, slower flow rate = slower ramp up. At very low flow rate, you're essentially pouring water onto the coffee puck and let it sit (some will seep into the puck) at 0 bar, and then very gently fill the headspace with water and eventually increase the pressure (gently).

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. The puck doesn't care what is above it - whether there is a 0.5 cm height of water column (Slayer) or >2cm (Rossa), as long as you're not pushing the water too hard into the puck which will create the resistance.

EspressoForge wrote:A Slayer uses an adjustable needle valve to slow the flow rate to the puck. Some lever groups have that integrated into the design, and some use a different external method. But this isn't exclusive to the Slayer, or even to a pressure profiling machine.

Yes, it uses needle valve for pre-brew flow rates.

I'm curious what lever groups have a need valve integrated into the design?
I'm yet to see anything that's anywhere near 1.5ml a second.

EspressoForge wrote:Strega may be capable to do a lot of variability, but without the dimmer mod, I don't think it's realistic. I tried counting seconds on my Strega but could never get repeatable results that I was happy with.

Ditto. I also found consistency harder to repeat.

My Strega would consistently do 10ml/s.
You could toggle the pump on/off, but I found flow would start between 1-3 seconds depending... If I had kept it, I would of dimmer modded.

EspressoForge wrote:Try to lower your pressure regulator to 1-2 bar on the L1 and grind the same as your Slayer. I bet you can get a similar shot with some work, I don't think cooling is much of an issue, it would be the same on any machine with a similar flow rate (and amount of metal). The low initial flow of a Slayer helps to do about the same thing, but there are multiple ways of achieving the same result. At least this is all from my experience. It's hard to exactly compare machines because they are complex systems.

L1 is boiler level only. I've played with boiler between 1.05 - 1.3. With the 1.3 being with longer PI's where the water would cool more.
Grind didn't change much - compared to Slayer levels.

samuellaw178 wrote:Also, I would like to 'dissect' the flow profiling on Slayer. In my opinion, the key to extremely fine grind (aka as in Slayer style shot) is not the flow rate itself. The flow rate is the indirect factor in determining the pressure ramp up. Faster flow rate = faster ramp up, slower flow rate = slower ramp up. At very low flow rate, you're essentially pouring water onto the coffee puck and let it sit (some will seep into the puck) at 0 bar, and then very gently fill the headspace with water and eventually increase the pressure (gently).

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. The puck doesn't care what is above it - whether there is a 0.5 cm height of water column (Slayer) or >2cm (Rossa), as long as you're not pushing the water too hard into the puck which will create the resistance.

I'll play with this. One could very slowly release the lever on the L1. Would be hard to be repeatable though.

Perhaps similar results to what John is getting above?

nickw wrote:I'll play with this. One could very slowly release the lever on the L1. Would be hard to be repeatable though.

Could you hold the lever at an angle where the flow is trickling out (then lock in the pf)? Can't wait to try this myself on my lever.

The downside of all these experiments on levers though, is that it will affect the temperature as alluded before. Nick, do you know what's the temperature profile like when Slayer is brewing this way(low flow rate)? I imagine the coffee will cool the water down as well, unless Slayer has a method for heating up the water temperature in the group/pf.

nickw wrote:Yes, it uses needle valve for pre-brew flow rates.

I'm curious what lever groups have a need valve integrated into the design?
I'm yet to see anything that's anywhere near 1.5ml a second.

Aside from adding a needle valve to any group.

The Bosco group I'm getting supposedly has either a check valve config or can be replaced with an adjustable valve. I don't know the lowest the flow will go yet. If the built in one doesn't work for me I may add another.

San Marco group also has a fill valve that the lever presses. I don't know if it's adjustable, but you can hold the lever partially to open the partially valve easily (according to videos, not first hand experience).

nickw wrote:L1 is boiler level only. I've played with boiler between 1.05 - 1.3. With the 1.3 being with longer PI's where the water would cool more.
Grind didn't change much - compared to Slayer levels.

Interesting, I was thinking of the L1-P, though I guess it would behave the same. The flow rate would seem to explain the difference.

samuellaw178 wrote:Could you hold the lever at an angle where the flow is trickling out (then lock in the pf)? Can't wait to try this myself on my lever. .

I already pull the lever to just above the point where water comes out, then lock the PF.
- If I don't: I get a ring around the outside of the PF at the beginning of the shot with more flow there (presumably because it's lifted/disrupted the puck from the vacuum effect due to the piston rising).
- When I do: I get a nice even saturation of the puck, and even flow throughout the basket.
Note: I'm using VST's.

samuellaw178 wrote:The downside of all these experiments on levers though, is that it will affect the temperature as alluded before. Nick, do you know what's the temperature profile like when Slayer is brewing this way(low flow rate)? I imagine the coffee will cool the water down as well, unless Slayer has a method for heating up the water temperature in the group/pf.

Re L1 temps:
On the L1, I've experimented with holding the lever at the point where water just trickles out. As it takes longer to fill the group, you need set the boiler to a higher pressure/temp, as the water cools off a lot. Once compensated for, it does allow for a slightly finer grind.

That being said, it's not that big of change. Combined with the fact it's more work and harder to repeat, I went back to the normal pull, 6 second PI, with a finer grind and lighter tamp. Much easier and more consistent from shot to shot, and coffee to coffee.

But once again, I'm using boiler level PI. With line level (4-5 bar area), this would probably have greater effect, and allow for an even finer grind.

Re Slayer temps:
There's not much space/volume between the puck and dispersion screen, and the dispersion screen and the group. Plus it's a saturated group, so the group is at brew water temp. So while the water does cool (while the coffee/puck heats up), there's no real issue there.

EspressoForge wrote:Aside from adding a needle valve to any group.

The Bosco group I'm getting supposedly has either a check valve config or can be replaced with an adjustable valve. I don't know the lowest the flow will go yet. If the built in one doesn't work for me I may add another.

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).