Marshall wrote:Thanks, Nicholas. I don't really have any interest in going down that path. This was more to satisfy my curiosity and correct some misinformation I had posted in other threads. E.g. Possible to install group-mounted pressure gauge on La Marzocco GS/3 MP?.

I'm very happy running my machine the way it is.

Marshall, I appreciate you taking the time to test the flow and post your findings.

HB wrote:I would need to compare parts diagrams, but I've always assumed the main difference between the Strada/Shotpuller grouphead and the GS/3 MP grouphead is the riser mechanism on the former has a hole drilled through it to allow for the grouphead pressure gauge. That is, no modifications are necessary, just expensive parts.

This is more along the lines of what I was thinking also. I figure at some point I'll be pulling this apart to replace the o-rings, and from what I assumed (also haven't studied the parts diagram) is that the riser just has a threaded hole, with a top mounted gauge. I may call Roger and waste a few minutes of his time, with useless questions.

Regardless of the ease or difficulty of the mods required to mount a manometer, that gauge needs some pressure changes worth measuring - and not just zero bars, three bars and nine bars for rest, line pre-infusion and brewing respectively. This would require, at core, a mechanism that increases the pressure in some significant and linear-ish and predictable manner as one moves the paddle to the left.

That would mean - I think - a pretty significant change to the GS/3 valve mechanism to change it from an (essentially) on-off valve/switch to a variable/progressive opening. (I'm assuming that electrically-controlled pump power variation is a wholly different direction, and I'm not asking about that here.)

I wonder if anyone cares to do pressure testing before rebuilding their paddle to encorporate the Strada gauge? It would be as simple as getting your hands on a Scace-2. That way, you would know ahead of time if the mod would add anything useful.

I mention this because it seems this thread has caused danetrainer (a member) to proceed with this mod.

I have a Scace 1 so I do not have any data to report there, it would be nice to see what would show on a Scace 2.

Anvan wrote:This would require, at core, a mechanism that increases the pressure in some significant and linear-ish and predictable manner as one moves the paddle to the left.

In discussions I've had with techs on the origional MP Strada vs this mod to the GS3 is that I should have a degree of profiling, but as we know, not the inherent repeatability of the EP model or programmable MP Strada.

Of course the gauge is not adding anything the machine doesn't already possess, just a means to visually see the dynamic pressure at the coffee puck. (this alone is worthy of having the gauge in my opinion).

Marshall has already shown different flow rates as the "windows" in the manual valve passage interact.

One thing that was brought up in conversations is the micro switch position is very critical and should not be changed from the factory setting. Those who have ventured into the MP group and removed this switch see that it has elongated slots that give it quite a range for pump activation.

The shaft for the Strada MP is identical except for the hole clear through (from top to bottom) and the threading to mount the fitting.

mitch236 wrote:That way, you would know ahead of time if the mod would add anything useful

I strongly doubt that it would, especially at home. Reasons:

1. It adds yet another variable to worry about and dial in. To dose, grind and temperature, which are all at least single numbers, you add a pressure/flow profile, which is a parameter that requires choosing a range of pressures over one or more time periods. By the time you dial in this collage, you'll be mostly through your bag of coffee.

2. It's a moving target, where, as the coffee ages (or ambient temp or humidity changes), you will have to redial.

3. Even professionals find it frustratingly difficult to repeat a profile with manual control. Then you change coffees and try to do it again.

Some people want a short throw shifter installed in their car, and others feel it adds nothing and is an unnecessary expense. There are 2 sides of the fence here that it "adds nothing".

Marshall wrote:I strongly doubt that it would, especially at home. Reasons:

1. It adds yet another variable to worry about and dial in. To dose, grind and temperature, which are all at least single numbers, you add a pressure/flow profile, which is a parameter that requires choosing a range of pressures over one or more time periods. By the time you dial in this collage, you'll be mostly through your bag of coffee.

2. It's a moving target, where, as the coffee ages (or ambient temp or humidity changes), you will have to redial.

3. Even professionals find it frustratingly difficult to repeat a profile with manual control. Then you change coffees and try to do it again.

I have to disagree. I don't think it's hard to repeat the profile I use. Just to be clear, I always use my EP in manual mode. Perhaps it is easier to control pressures on the EP than the MP, that I don't know. I also will add that I don't do what some might think is pressure profiling. I use flow control. That isn't a moving target. The pressures required to get that flow may move, but what the flow looks like and keeping it constant is not variable. That's why I don't see why it's so important to know what pressures you are running. On the EP, the machine is capable of achieving 12+ BAR so I use the pressure readout to get to the initial 9 BAR but after that, I don't know what pressures I'm using. If the MP's maximum pressure is 9 BAR, then there's really no reason to know what pressures you're using.

I do know one thing for sure; I will never go back to non-profiled brewing. The shots are so much sweeter and have incredible balance when flow is controlled. The consistency of quality proves that I can repeat my profile time and again.

mitch236 wrote:Perhaps it is easier to control pressures on the EP than the MP, that I don't know.

Yes. The MP is very fiddly compared to the EP in terms of adjustment. You would have to use much more fine manual control. The area on the paddle where the pressure changes really happen on the MP is much narrower than the EP, which leverages basically the entire travel of the paddle.

mitch236 wrote:That's why I don't see why it's so important to know what pressures you are running. On the EP, the machine is capable of acheiving 12+ BAR so I use the pressure readout to get to the initial 9 BAR but after that, I don't know what pressures I'm using. If the MP's maximum pressure is 9 BAR, then there's really no reason to know what pressures you're using.

So you have a Strada so you surf between 9 & 12 bar??? I'm confused.

Personally I'm not interested in achieving any pressure above 9 bar, my interest is in the ramp from pre-infusion and the trailing end of the shot.

danetrainer wrote:Personally I'm not interested in achieving any pressure above 9 bar, my interest is in the ramp from pre-infusion and the trailing end of the shot.

Why not? You haven't actually tried it, have you?