I do in fact completely understand the difference, but it would not be that hard to imitate a Slayer shot with pressure profiling if that was the goal. Slayer chose what they did because it's a simple, easy to set up, very consistent way to get long pre-infusions. An hour in a discussion with Jason listening to him try to give me the marketing side until he understood I actually knew what I was talking about and then we could talk about how it actually worked and the choices he'd made.

None the less, an Arduino and a suitable pressure or flow sensor and some way to control whatever was being measured would allow for any arbitrary profile, pressure or flow. See Decent for example.

Ira

ira wrote:I do in fact completely understand the difference, but it would not be that hard to imitate a Slayer shot with pressure profiling if that was the goal.

Yes, but the Slayer method can't be imitated with just a variable speed pump, like the Strada MP or Vesuvius, at least when the machine is plumbed in. You need a variable flow restrictor like the Slayer needle valve to reduce the flow below the incoming line pressure. In my modified GS/3, I've been able to use a high-quality pressure regulator to get the line pressure down to 1-2 BAR, but that limits the max pre-infusion time to 10-15 seconds. A needle valve is needed to make it longer.

I think it can be done with a variable-speed pump if the machine is fed from a reservoir, but I'm not sure if the pump can be set to a low enough speed to produce the target pre-infusion time and still have enough power to draw water out of the reservoir.

You might be correct that the implementation using currently available pieces might limit our ability to match any solution with any other, but in theory if you put a flowmeter on a Slayer and set up a flow controlled machine to match the flow you should get similar results.

Ira

Not only does the new GS/3 allow you control over the flow and pressure ramp up, you can also move the paddle to reduce pressure and flow. For example, I'll start my shot and move the paddle until I see 3 bars in the group manometer, if I leave the paddle at the point it would maintain pressure at 3 bar for the whole shot. I think they accomplish this by dumping the excess flow to the drain box, otherwise you would hit pump pressure (which is set at 9bar by the factory). After I see the puck being saturated, I'll move the paddle to full brew pressure and finish the shot. I've tried a few times to lower the pressure near the end of the shot to mimic a lever, but I'm not tasting a difference in shot. I'm still developing my palate so that doesn't surprise me. Anyway here is a nice link to the technical bulletin for a Linea PB, which had the valve before the GS/3.

http://nuovaricambi.net/en/content/news ... w-mp-valve

jgirl125 wrote:I think they accomplish this by dumping the excess flow to the reservoir, otherwise you would hit pump pressure (which is set at 9bar by the factory).

Not the reservoir. I'm pretty sure they dump the excess flow to the drain box via the exhaust pipe at the back of the boiler.

jgirl125 wrote:I've tried a few times to lower the pressure near the end of the shot to mimic a lever, but I'm not tasting a difference in shot.

Not surprising -- it's pretty subtle. I find that it can take some of the edge off a light roast, but it's not a dramatic effect.

The biggest effect you can get from profiling is to pre-infuse very, very slowly -- 10-15 seconds or more until the basket fills and you see pressure rising on the group gauge. Then slowly move the paddle left until you hit max pressure. Doing this will require a much, much finer grind, which is what is often needed to tame very light roasts that are hard to extract otherwise. Shot times of 40, 50, 60 seconds or more are not uncommon with this method. Again, it's only appropriate for very light roasts that are too sour when pulled with normal espresso parameters.

Peppersass - Not the reservoir. I'm pretty sure they dump the excess flow to the drain box via the exhaust pipe at the back of the boiler.

Whoops, edited my post on that one. Thanks.

Just to jump in here, I made the Strada Mod to my GS3, and I find it very easy to repeat profiles on the machine. I created a "reference label" on the top of the group head. I marked lines that I have set for pre-infusion and full extraction, and I can ramp up or down however I like. I also have a friend with a Slayer. Personally, I don't see all the hype on the Slayer and its needle valve. In a blind test, I don't think 99% of the people would know the difference. My only gripe on the GS3 is the cheesy water level rigging on the reservoir. I'll have to think about making the conical valve mod. Probably will do it since I like to tinker.

The GS/3 has a tank and the Slayer does not if that means anything to you.

txrpls wrote:Just to jump in here, I made the Strada Mod to my GS3, and I find it very easy to repeat profiles on the machine. I created a "reference label" on the top of the group head. I marked lines that I have set for pre-infusion and full extraction, and I can ramp up or down however I like. I also have a friend with a Slayer. Personally, I don't see all the hype on the Slayer and its needle valve. In a blind test, I don't think 99% of the people would know the difference. My only gripe on the GS3 is the cheesy water level rigging on the reservoir. I'll have to think about making the conical valve mod. Probably will do it since I like to tinker.

That's what I'm trying to find out:
The difference between the Strada Mod and the New Conical Valve upgrade on new GS3.

Anyone care to shed some light?

Peppersass wrote:Yes, but the Slayer method can't be imitated with just a variable speed pump, like the Strada MP or Vesuvius, at least when the machine is plumbed in. You need a variable flow restrictor like the Slayer needle valve to reduce the flow below the incoming line pressure. In my modified GS/3, I've been able to use a high-quality pressure regulator to get the line pressure down to 1-2 BAR, but that limits the max pre-infusion time to 10-15 seconds. A needle valve is needed to make it longer.

I think it can be done with a variable-speed pump if the machine is fed from a reservoir, but I'm not sure if the pump can be set to a low enough speed to produce the target pre-infusion time and still have enough power to draw water out of the reservoir.

The Vesuvius is always taking water from the reservoir - even when plumbed in. BTW I can do pre-infusion without the pump. I would not know what pressure, but the flowrate without any resistance is around 30ml in 6.5 seconds straight from the screen into a shotglas.