Posted Thu Mar 7, 2013, 9:14am Subject: Does a flow restrictor improve shot quality?
I am wondering if a flow restrictor improves shot quality or not? I am thinking of trying to add one to my Silvia just for fun. I think larger machines like the rocket have them as well as commercial one too. Do they play a big role during extraction?
Posted Thu Mar 7, 2013, 10:51am Subject: Re: Does a flow restrictor improve shot quality?
The machines that have flow restrictors are heat-exchanger (HX) machines. Your Silvia is a completely different breed of machine - single boiler dual use (SBDU).
As I understand it flow restrictors are used in HX machines to create a pressure ramp profile to achieve pre-infusion or dampening of the coffee grounds.
There are no extra chambers in a SBDU grouphead to fill by flow restriction to acheive pre-infusion.
Pre-infusion in SBDU is usually done (from my experience) by running the pump for a few seconds (not letting full pressure build up), turning it off for a few seconds, and then turning it back on to brew. This is what the pre-infusion function on my old Silvia's Auber PID did. Run for 2.5s, off for 2.5s, brew for 28s.
Flow restrictors are also used in an HX thermosyphon loop to control the temperatures, which is completely inapplicable to a SBDU.
Someone PLEASE correct me if I'm wrong on any of this.
Posted Thu Mar 7, 2013, 12:37pm Subject: Re: Does a flow restrictor improve shot quality?
Thanks. I was just wondering. A video of a bottomless pull on a rocket machine gave me the idea. I didn't know it had to do with pre infusion. I simply wanted to slow a pull for optimal extraction which I can do by bleeding some pressure with the steam valve.
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