High flow rate = low shot temperature in HX? - Page 3
- PIR EasyCompany
- Posts: 2
- Joined: 13 years ago
Hi I've been trying familiarize with all details (still learning). In short I think I'm having a similar issue with my ECM Giotto where I'm getting an excessive water flow rate. And if I understand Frank I cannot (or should not) measure my flow rate without resistance(0bar)?frankmoss wrote:That's at 10 bar. Your 750mL/min is unrestricted (ie at 0 bar), right? So it's not comparable.
Can I measure my water flow rate with a blind pf and calculate the amount at the return?
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- Posts: 151
- Joined: 14 years ago
The point Frank was making is that the unrestricted flow rate can not be compared to the pressurized flow rate quoted in the pump manufacturers material. I believe the unrestricted flow rate should be somewhere around 500ml/min.And if I understand Frank I cannot (or should not) measure my flow rate without resistance(0bar)?
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- Posts: 125
- Joined: 14 years ago
Thanks for explaining that. Basically, flow rate is dependent on pressure in a vibe pump, as erics's graph showed. According to that graph, completely unrestricted (ie 0bar) flow rate should be about 750 mL/min for your pump. Therefore, erics suggested that you might be missing a gicleur somewhere. Either way, that flow rate is not ridiculous and shouldn't cause the problem you described. The stuck one-way valve was likely the culprit.
- PIR EasyCompany
- Posts: 2
- Joined: 13 years ago
Hey jarvis,
Thanks for the info...Just tried it and I got 500ml/min "Dead On!", I also tried measuring the flow from the return with a blind pf (9bar) and I got 200ml/min after the pre-infusion cycle...Now I have to figure out why I cant get perfect crema...It will require some further inquiry but since I have a vibe pump I suspect that I should increase my blind pf gauge to around 11bar so I can get ~9bar on a shot at the pf.
btw Canadiens are currently playing the Leafs and it's still scoreless.
Thanks for the info...Just tried it and I got 500ml/min "Dead On!", I also tried measuring the flow from the return with a blind pf (9bar) and I got 200ml/min after the pre-infusion cycle...Now I have to figure out why I cant get perfect crema...It will require some further inquiry but since I have a vibe pump I suspect that I should increase my blind pf gauge to around 11bar so I can get ~9bar on a shot at the pf.
btw Canadiens are currently playing the Leafs and it's still scoreless.
- cannonfodder
- Team HB
- Posts: 10510
- Joined: 19 years ago
In the end, the only flow rate that matters is the flow rate you have while pulling a shot, provided you do not have a dying pump and have super low volume. You can run a machine without any flow restriction, as long as your distribution, dose, tamp is correct you will get the correct extraction flow rate. The flow restrictor makes it easier to pull a shot especially on rotary pump machines. I have played with changing the restictor before to lower the rate of infusion but in the end, as long as your coffee cake is 100%, your flow rate during a shot will be just fine. If you are flushing water through the machine with the portafilter off, then yes, higher flow rates will have a faster drop in temperature. Restrictor or not you are still only pulling approximately 2oz in 28 seconds.
Dave Stephens