Hello Everyone

I have been looking into the differences between the slayer single head and the GS3 MP.

I have a question regarding the profiling mechanism between the two mainly concerning pre-infusion.

It seems to me that although they use a different mechanism to introduce a low flow during the pre-infusion, it seems to me that they are achieving the same result. If there is any, what is the main difference these machines when it comes to pre-infusion? If I am not mistaken, technically the GS3 is able to pull off a "slayer" shot.

Thank You

-R

rswum wrote:If I am not mistaken, technically the GS3 is able to pull off a "slayer" shot.

Correct. There is a difference, however.

As you probably know, the Slayer uses a precision needle valve to set the pre-infusion flow rate, while the GS/3 MP uses an opening in the conical valve that's set by the position of the paddle. So the Slayer pre-infusion flow rate is precisely repeatable, whereas the GS/3 MP pre-infusion flow rate depends on the operator hitting the same mark (i.e., opening size) without any clues other than the approximate position of the paddle.

That said, owners of the GS/3 MP, even the older non-conical model modified with a group gauge, say that they can hit the mark consistently enough to get the desired pre-infusion flow rate. Also note that lever machines are popular for their ability to control flow and pressure, which is manual as well.

There are some other differences. The GS/3 MP is able to do pressure profiling, so the ramp to full pressure can be varied as the basket fills, and pressure can be varied after full pressure is reached. This allows a popular technique of reducing pressure after the peak to keep the flow rate constant. This can "tame" a light roast by increasing the contact time. It may also reduce the tendency for the puck to break up or channel in cases where grind and distribution aren't perfect. The Slayer's flow and pressure can't be varied during the shot -- the ramp to full pressure is a function of the needle valve setting, and max pressure is a function of the gear pump speed, which is preset before the shot. The gear pump doesn't have a bypass valve, so the pressure does slowly decrease as the puck loosens, but there's a limit to that and it's not the same as being able to ramp the pressure down to flatten the flow rate. However, I believe there's an option to switch the needle valve back in after peak pressure to ramp the shot down more slowly, albeit with no dynamic control.

TL;DR

1) GS3/MP (the current conical valve version):
Pump runs at full power no matter the paddle position.
During low flow and pressure, the excess water from the pump that is not needed during pre infusion is pumped into the drip tray (or down the drain if plumbed out). This "method" has been nicknamed, the "water wasting" method.

2) Slayer:
Pump runs at full power no matter the paddle position
But it has two water paths...
-With the paddle at the pre brew postion, (Slayer in-house parlance for pre infusion), water is diverted to one of the paths, with a needle valve in it that the user has pre set to whatever low flow rate is desired during pre infusion, say 1.5ml/s.
-When you move the paddle further, to the regular brew position, the water is diverted from the pre brew path, to a regular brew path like any other espresso machine. This method does not waste water. All water pumped, is used.

3) Some Others: You didn't ask about it but...
There are other machines with a single brew path and a needle valve that you adjust on the fly (Slayers is not intended to be adjusted on the fly, it is inside the machine). The pump runs at full power and you set your needle tighter for the pre infusion, and open it as you like, to transition into regular extraction. This offers an advantage over Slayer in that you are not limited to just two speeds. You can for example make a small adjustment to slow the flow in mid extraction if it looks like it's coming out too fast. This method also does not waste water. All water pumped, is used.

4) Custom: Some people have made custom controllers for gear pumps, where instead of the pump running at constant speed, the pump speed can be varied by the user. These generally require custom controllers made by savvy user/modders.

HTH

-Peter

What Sir Peter said above. For reference from the Slayer manual:

Flow rate
At the studio, the flow rate is set at 40 grams per 30 seconds and correlates
with the duration of pre-brew: increased flow rate will lead to a shorter pre-brew
time and decreased flow rate will lead to a longer pre-brew time.

At 40 Pre Brew time is around 30 seconds to first drips for me. I think at 60 it's more like 20 seconds.

Pre-Brew is paddle half way and Full-Brew is all the way left.

The manual also states:

Extended Pre-Brew: Enhancing Sweetness
When espresso lacks sweetness, the pre-brew phase may be extended to extract
more of the naturally-sweet oils:
1. Follow "Slayer Shot" steps 1-5 above, but allow the espresso to continue
extracting in the Pre-Brew stage until it has dispensed up to 7 grams
(0.25 ounces).
2. Move the brew actuator to the "full brew" position,....

I think its fairly common to return the paddle to Pre-Brew for the last portion if you want to slow things downs. Apparently it reduces pressure down towards 3 bar but the puck conditions make it slightly different each time.

Peter's water point is important if you aren't plumbed in and are making water.

Good luck. Either would be great.

Thank you all! This information has been extremely helpful in understanding a bit more about these two machines.

Sir Peter, I read through the whole BDB Slayer Forums where you, Jake and a few others have managed to utilise the needle valve from the water spout and reroute it to the group head. I will most definitely be doing this soon!

As for the GS3 water wasting method, I was wondering if you can explain the purpose of this. Why does this occur on the GS3 when there are machines with a single brew path and a needle valve that still utilise all of the water pumped?

Sir Peter™...

The way I understand it, the GS/3 MP and stock BDB using "water knob trick" divert water from the puck, but also pressure as well. Conversely, with the Slayer and Pseudo Slayer™, since no water and hence no pressure is being bled off, it will slowly build all the way to very close to 9 bar - even with a very low flow such as 1.5mL / sec or whatever.

DaveB wrote:Sir Peter™...

The way I understand it, the GS/3 MP and stock BDB using "water knob trick" divert water from the puck, but also pressure as well. Conversely, with the Slayer and Pseudo Slayer™, since no water and hence no pressure is being bled off, it will slowly build all the way to very close to 9 bar - even with a very low flow such as 1.5mL / sec or whatever.

9 Bar and more or less depending on where you set the brew pressure %. I recently adjusted mine for some changes I made in my cart system:
Espresso Cart - Goodbye Plumbed In

From the manual

Adjust Brew Pump Pressure
At the Slayer studio, the brew pump pressure is set at 9 bar. Actual brew pressure,
as indicated by the pressure gauge on the face of your machine, will be influenced
by incoming water pressure (line pressure) at your location. Adjust the brew pump
pressure with the following steps.

DaveB wrote:The way I understand it, the GS/3 MP and stock BDB using "water knob trick" divert water from the puck, but also pressure as well. Conversely, with the Slayer and Pseudo Slayer™, since no water and hence no pressure is being bled off, it will slowly build all the way to very close to 9 bar - even with a very low flow such as 1.5mL / sec or whatever.

I forgot to include this difference in my post.

When the Slayer has filled the basket, pressure builds to whatever pressure you set the gear pump speed to produce at the max, nominally 9 BAR. That's because the gear pump is running at that speed throughout pre-infusion and the rest of the shot, and there's no diversion of excess pressure. Consequently, when the solenoid is activated to bypass the needle valve, there's no ramp because the pressure is already at the max (assuming you programmed the time to activate the solenoid to be after the basket has filled.)

The GS/3 MP conical, in contrast, bleeds off the excess pressure. So the max pressure reached when the basket fills is determined by how much the brew and exhaust openings are exposed. The gauge on the group head will show what that pressure is. As soon as the pressure starts rising, or when it maxes out, you quickly push the paddle fully to the left, closing the bypass hole and fully opening the brew hole, and the pressure rises to the max set by the pump. If you push the paddle to the left more slowly, you slow down the ramp to max pressure.

My tricked-out GS/3 AV works a little like the GS/3 MP with conical valve, but without the water diversion. I replaced the rotary pump with a gear pump (and lots of other stuff, but that's not important here.) I set my high-quality line pressure regulator to 1-2 BAR for pre-infusion with the gear pump off, and when the basket fills I ramp the gear pump up to the speed that produces 9 BAR at the puck. I can do that slowly or quickly.

So the difference is a very fast (instant?) ramp to full pressure by the Slayer, or a potentially slower ramp controlled by the GS/3 MP user. Both methods allow long, slow pre-infusion, which may be needed to fully extract a very light roast, but I don't know whether the different ramp profiles make any difference in the cup. Our member AssafL, who modified his GS/3 AV in a manner similar to how I did it, added a needle valve to simulate what the Slayer does. I believe he has a theory that there's less disturbance to the puck in the Slayer case.

Peppersass wrote:I forgot to include this difference in my post.

The GS/3 MP conical, in contrast, bleeds off the excess pressure. So the max pressure reached when the basket fills is determined by how much the brew and exhaust openings are exposed. The gauge on the group head will show what that pressure is. As soon as the pressure starts rising, or when it maxes out, you quickly push the paddle fully to the left, closing the bypass hole and fully opening the brew hole, and the pressure rises to the max set by the pump. If you push the paddle to the left more slowly, you slow down the ramp to max pressure.

So if I am understanding correctly, although these two machines are both achieving low flow to the puck during pre-infusion, because of the bypass hole on the GS/3 MP conical, the pressure will always be limited to however much the user has turned the paddle. The slayer on the other hand, if, hypothetically, the paddle was left in the middle position for a very long time, will reach 9 bars of pressure in the basket. So the main difference is in the moment the user decides to engage full pressure, the slayer has 9 bars constantly ready unlike the GS/3 which has to ramp up to the pressure. Please let me know if I am misunderstanding something.

I am very curious about AssafL's theory behind how the slayer may causes less disturbance. All of this is just me trying to get a better understanding of these machines and I am very grateful to have you all provide me with this information

Thank You.

Peppersass wrote: When the Slayer has filled the basket, pressure builds to whatever pressure you set the gear pump speed to produce at the max, nominally 9 BAR. That's because the gear pump is running at that speed throughout pre-infusion and the rest of the shot, and there's no diversion of excess pressure.

Is it because of the gear pump?
Lelit Bianca uses the rotary pump. As the coffee starts to drop, it cannot reach 9 bar with the low flow rate, so the extraction pressure can be adjusted on the fly.