This subject's probably a decade out of date, but can I ask:

1) Is there enough boiler pressure to do any kind of worthwhile preinfusion on a single-boiler? And/or
2) Is it worthwhile to open the 3-way valve brewpath in advance of pump switch-on to reduce puck trauma?

I found a two-year-old thread where poster Helgep wrote:

From the Silvia diagrams that I have found, it seems that the boiler water outlet leading to the group head is high in the boiler, and that this is what regulates the water level. If so, then opening the three-way valve without the pump running will likely push steam to the group head instead of water. I can see scenarios where the water level can be made to be higher, but that will not always be possible or practical.

So the pump may have to run after all. If so, the easiest way to ensure as gentle a preinfusion as possible might be an override button to temporarily disable the pump (while leaving the three way valve in the brew position) between the preinfusion stage and the actual brew.

Is this true that without the pump running, only steam will enter the brewpath? If this is so, I guess it might still assist with a soft start if not a preinfusion.

I don't know whether it's already been tried but the mod I'm considering is to insert a Dayton 2A561 delay-on relay into the pump's electrical feed.



This would wait a predetermined time before feeding power to the pump so giving the 3-way valve a headstart. Others will no doubt have tried this kind of approach as it's something I remember discussing online years ago, but using a push-switch rather than a delay relay, so I'd appreciate hearing anyone's findings and opinions. Thanks.

IMO, there are advantages to slow pressure ramp and/or pre-infusion. But for most existing machines, adding a dimmer or variac to the pump would be the best way to do that. If you have something to measure flow and a micro-controller, you can do more complicated but repeatable things.

Recently, I've been experiment with prefinfusion with my silvia. I did some rewiring and was able to disable the pump from the brew switch, the brew switch now just opens the 3-way valve and the pump is turned on via the hot water switch.

My preinfusion procedure.
1. Switch on the pump and 3-way valve.
2. After 3 secs turn off the pump, leaving the 3-way valve open.
3. Wait for another 7 secs and turn on the pump.
4. After the pull, switch off both the pump and 3-way valve.

Some observations:
- There's not enough pressure in the boiler to be able to do a preinfusion using the 3-way valve, there's little or no flow from the brew head. If your machine is plumbed in it may be plausible to preinfuse using the 3-way valve.
- Dont think opening the 3-way valve first would help in a softer start/ramp up.
- The espresso seems to taste better with preinfusion.

Thanks for your replies, useful to read.

Some observations:
- There's not enough pressure in the boiler to be able to do a preinfusion using the 3-way valve, there's little or no flow from the brew head.

That's the key point really. So it's going to take a more elaborate approach to see useful improvement.

regards