FMU users -->Bastaad here is data.

[cygnusx1]

We wanted to see how the BEGI FMU regulates fuel pressure at different boost levels and onset gains. The term "onset gain" is a bit misleading as I could not really see changes the RATE of fuel pressure rise by changing gain values (T number of turns). This could also be a function of the semi-crude gauges on both the compressor and the fuel rail.

 

Hardware:

BEGI 2022 FMU (2025 w/o spring)

Walbro Pump (Holley HLY-12-920) from Summit Racing

16g fuel pump wire

Stock 280Z sized fuel lines and filter.

 

Base Fuel Pressures:

Vacuum Connected FP=32psi

Vacuum Disc'n'cted FP=42psi

 

Pressure Supplied to FMU and FPR from compressor 15psi

T=onset screw turns IN

2.5T = 51psi

3T = 55psi

3.5T = 59psi

 

Pressure Supplied to FMU and FPR from compressor 10psi

T=onset screw turns IN

2.5T = 46psi

3T = 48psi

3.5T = 50psi

 

I hope this helps you tune your FPR. Don't take my numbers absolutely as my gauges could be off by a couple of PSI in either direction.

 

Oh and with the onset gain fully closed, I hit 100+psi fuel pressure at 10psi boost.

 

All these tests were done at idle so fuel capacity did NOT come into play.

[Guest bastaad525]

w00t thanks Cygnus that gives me a better idea on how sensitive this thing really is. I agree I didn't expect to see a definate RATE increase... I think the thing operates at just one set rate, the only thing you're varying with the bleed is how much boost you're allowing to hit the diaphram, so maybe it operates at say, 8:1 all the time, but if you're running 15 psi of boost and bleeding off 10, you're only increasing fuel 40psi. It's good to see that it does increase pretty linear with boost increase.

 

 

BTW yours definately seems to operate at a much lower level than mine for whatever reason. I have the 2025, and I did back the adjustment screw all the way off of the spring in there (you could feel the screw 'go loose') maybe I should make it a point to remove it completely?