I work in high performance automotive so when I was contemplating ways to turn my 2 group HX Rancilio S20 into a pressure profiled machine the FPRs kept calling my name.

My thinking is put them inline right before the group head and have the FPR dialed into pre-infusion pressure. Then using a separate hydraulic air lever that delivers a set psi (in air) you can ramp up the pressure simply based on the location of the lever as most FPRs ramp up on a 1:1 scale. (The other option is simply use the steam pressure from the boiler and an FPR with a rising rate scale of 1:5 let say so u can use a valve but perhaps less control and variability is introduced).

1) set FPR to lets say 50 psi
2) have air lever produce 80 psi max
3) start shot at 50psi, pull lever and hold adding 80psi to total 130 then slowly back off manually ala slayer action

Yes no?

Here is how these things work, you can get them with a return or without, on an HX a return would probably be required as temps would rise if the water is static, return could enter the boiler although that could introduce new problems:
-engine vacuum in diagram is actually +pressure from the intake manifold and it is where the controlling pressure is derived from

Seems like a nifty idea. How quickly and accurately does it settle at a given pressure? Food safe?

Mark

pressure changes are instantaneous based on input pressure...the lever creating the pressure could create a delays but there shouldnt be an issue because you need virtually no flow, just positive pressure. Heck you could use a bike pump

-correct on the food rating, my concern would be gaskets or the diaphragm material, you can get FPRs in brass though

-some fuel pumps end up heating the fuel well pass 100f so i think that should be ok (I'm asking a supplier about it but I doubt they'll know

truemagellen wrote:I work in high performance automotive so when I was contemplating ways to turn my 2 group HX Rancilio S20 into a pressure profiled machine the FPRs kept calling my name.

Greg Scace, inventor of the Scace Thermofilter and pressure profiling controls for the espresso industry, also began in high performance auto (Watkins Glen). If he doesn't respond here (he probably will), you should contact him. I'm sure he had good reasons for not choosing automotive hardware (unless his black box contains a secret fuel injector, in which case I take this all back ).

Thank you Marshall. I will seek him out.

Randy G. wrote:Two problems come to mind-
- They are not designed to be used with such a hot fluid.

Pumps pump cold water anyway.

I guess I could put the regulator right after the pump but then run the diverted water back into the intake of the pump...so it will function like an adjustable bypass on the fly? or will i just make a big friggin mess

This is for my house so I don't need electronic position control....and would prefer to keep costs low so even more reason to stay away from electronics.

Randy G. wrote:Fromm the OP: "My thinking is put them inline right before the group head...."

Ah I missed that bit. Excuse me.
I assumed he'd put it on the cold side of the HX.