[Jeff Alton]

Originally Posted by winders

Fuel pressure regulators go after the fuel rails before the fuel is returned to the tank.

The AEM 25-302BK FPR can be plumbed in series or parallel. If running in series, as proposed by the OP, you just use one of the inlet ports and plug the other.

If running in parallel, you would use both input ports on the FPR as this diagram shows:



The line with the Y plumbing is from the fuel pump.

Regardless of system design, you should put a filter somewhere before the fuel rails. The parallel setup is certainly "better"...but not required for most applications under 600 HP. Heck, my 450 HP race engine uses an in series fuel rail setup with zero issues. I would recommend a fuel damper be used in the system. My FPR has a damper built-in and it works great. I am using a Radium FPRD-RA fuel pressure regulator damper.

Scott's diagram is correct, and the way we do it.

IN to both rails, the way shown or a tee at one rail depending on your installation needs. You can plumb the inlet to Both rails as you see fit. Then, BOTH rails feed OUT to the regulator, which then has a single return line. Pretty simple and correct design.

Cheers