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Flow control device - Pressure reducing valve (on commercial coffee machine like Gaggia Classic)

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Hi all ! 

First I must say I am new to the forum but I have done lots of research on the mechanics of a coffee machine and know almost everything about them (except electronics).

I had an idea: I wanna buy a used Gaggia Classic and try every mod I can do to it (PID, Pressure Gauge, OPV mod ...) I want to try and mod the flow of the machine, allowing it to dynamically go from 2 bar to 9 and slowly back to 0. 

I have seen there is mainly one option to do that: get a cheap dimmer that regulates the current and plug the pump to it (although I would have to switch the Ulka pump with a Invesys one). I find this to be an easy mod that does the work for fairly cheap. But I thought there might be a cleaner mod in order to regulate the flow, and in my mind I think this is very very similar to the mod you can do on a e61 group head to relate the flow (for example with this kit e61 Group Flow Control Device).

So what I'm talking about is fitting a pressure reducing valve (like this one: Pressure regulator with Gauge) to the tube connected to the pump, in order to have incoming water pressure up to 12 - 15 bar and the outgoing pressure to be set during brewing dynamically. Of course modding the wheel of the pressure regulator device to come out of the machine and turn it as one wishes.

I haven't seen anything like that done by anyone so I want to ask you if something like that would work. I think one problem of this pressure regulator device might be that in order to control the flow (let's say from 0% to 100%) you might have to turn it many times, don't know but it could be 5 or 10 complete turns (maybe?).

Please let me know what you think about it. Thank you in advance for sharing your knowledge, and if someone might have the tools to try it themselves I think this would be awesome.

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Just a quick question. How come you say you would need to change the Ulka Pump if you were to put the dimmer switch online to control the output of the pump?

I've not heard of this and am looking to do the dimmer mod to my machine with uses a pump like Ulka or it may be having a Ulka pump depending on how my ebay claim for a burnt out pump goes. If what your saying is right then maybe I should be looking at a different pump, and how come the Ulka Pump is no good for the dimmer mod??

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Hello, thank you for answering although didn't help much with the idea I had of implementing a pressure regulator valve. 

About the Ulka pump I have seen in many threads online and on some videos on YouTube that the Ulka pump doesn't really work well with a dimmer, it just turns off and on when you dim it. I would say that is not really ideal to extract a good cup of coffee, although it kind of does the job because you can turn it off at around 2 bar, then wait 5-10 seconds and then turn it on to 9 bar for extraction without having to turn of the switch of the machine resulting in the 3-way solenoid valve opening and finishing your extraction.

In many forums I have seen that the Invensys pump (Invensys pump eBay) is much better at this, actually adjusting the flow on the go as you turn the nob on your dimmer.

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