Here's a picture that illustrates how the Speedster routes water through the grouphead (cover removed for photo), and how it helps achieve excellent intrashot temperature stability:



When you pull a shot, water flows from the boiler (underneath) up through the aqueduct "A" into the grouphead "B". It then goes back through the gicleur "C", through a copper tube to the three-way valve "D", through another copper tube up the aqueduct and to the dispersion block below "E".

In all this back and forth movement the brew water equilibrates in temperature with all the water in the aqueduct and the group. Because of their exposed position, the aqueduct and group run about 4F lower in temp than the boiler.

Cleaning/changing the gicleur is pretty easy, you just have to remove the group cap and unscrew the gicleur with a 3mm hex wrench. Please don't ask -- duh -- how long it took for me to figure out where the gicleur was.

So how are the shots? Seems they have a little better mouthfeel and a little clearer flavor profile compared with my venerable Tricked-out Silvia. I haven't seen a huge difference yet, and it's tricky setting things up so that one is really comparing apples to apples (eg, making sure temperatures, pump pressures, preinfusion, etc are reasonably equal). Taste testing continues....

Excellent, thanks for the great post. Out of interest, does anyone know if this back and forth arrangement is how it works with other self bleeding saturated groups also (Synesso in particular) or is it uniquely Kees?

Cheers and Merry Xmas to all.

AndyS wrote:Here's a picture that illustrates how the Speedster routes water through the grouphead (cover removed for photo), and how it helps achieve excellent intrashot temperature stability:

When you pull a shot, water flows from the boiler (underneath) up through the aqueduct "A" into the grouphead "B". It then goes back through the gicleur "C", through a copper tube to the three-way valve "D", through another copper tube up the aqueduct and to the dispersion block below "E".

In all this back and forth movement the brew water pretty much equilibrates in temperature with all the water in the aqueduct and the group. Because of their exposed position, the aqueduct and group run about 4F lower in temp than the boiler.

This is really cool, Andy. It reminds me of another aqueduct I visited recently in France, le pont du gard:

ken

gyro wrote:does anyone know if this back and forth arrangement is how it works with other self bleeding saturated groups also (Synesso in particular) or is it uniquely Kees?

Didn't seem to be that way on the GS3 prototype that I tested (photo below). I believe the water pickup point was down near the 3-way valve. And if I remember what Bill Crossland told me, the 3-way had a very small orifice (~0.6mm), so a separate gicleur wasn't used.

When you say "self bleeding saturated groups," are you referring to the owner's bank account?

Ken Fox wrote:This is really cool, Andy. It reminds me of another aqueduct I visited recently in France, le pont du gard:<image>

Looks pretty, but can it make good coffee?

Neat setup -- a perfect picture book counter flow heat exchanger. This means the temperature throughout the shot will pretty much stick to the initial group head temperature no matter what the brew boiler is doing. The brew boiler temperature only matters to set the initial group head temperature at idle.

The whole thing can drift if you make shot after shot unless that aspect has been calibrated as well. But still, this seems a much better piece of engineering than the initial LM version of the group.

As impressive as that group is, the welding of the group head to the stem is pretty impressive too. That's a pretty confined area to get a tig in there.

The water path of the GS3 is indeed different, also the serial models have the same setup:



I am wondering about the temp. stability and the location of the water inlet. I would expect it to be lower, is there a significant offset between coffee boiler temp. and output? Any chance to apply the Scace?

Have you connected it to direct water?

Best,
- Malte

the_deal_maker wrote: is there a significant offset between coffee boiler temp. and output? Any chance to apply the Scace?

Have you connected it to direct water?

Hi Malte:

The Scace says that the brew water temp is about 4F lower than the boiler temp. But I adjusted the PID controller to compensate for that. So now the display reads very close to the brew water temperature.

Yes, the machine is connected to direct water (that's the only way it operates).

Thanks,

very nice picture - seems that you are very talented in Photoshop. I am still undecided towards the Speedster vs. the GS3 paddle. I love the design and outer appearance of the Speedster and Kees is a guarantor in terms of quality. On the other hand the GS3 paddle is a full automatic, fully integrated machine, that gives you manual control over the brew procedure. Haven't figured whether it is possible to control the pressure itself step-less through the paddle. It might be similar to the Speedster off/infuse/brew.

The Speedster is such a beauty... I should go for it... however the GS3 paddle is also very tempting.