FPR Position

[pysical]

I don't know much about fueling and please excuse my ignorance in this but wanted to see what the main pros/cons of each of these external FPR positions are?

First image would be putting the FPR on the return line. By doing this I guess it maintains the pressure behind it? If I had 2x 450's running is this going to cause my LPFP sensor to read super high?

Second image would be the external FPR before the sensor.

 

[CAA]

First pic is one way to make it, is correct.
If you make the assembly as in the second pic you are doing nothing, you need to attach a return line in the middle port of the FPR, that's the port for return to the tank.

 

[martymil]

1st one is the best for pi but don not run a boost reference line to the fpr, our lpfp fuel pressure is static otherwise it will throw shadow codes.

I found the EKP to overheat trying to run with a boost reference line as its trying to bring the pressure back to the preset value

If you want to run the second system you have to put the return line onto the fpr and will become a dead head system.

Not great for pi as when on cruise the fuel will get to quite hot in the rail, fuel has a boiling point of 100 to 435f according to the caltex data sheet.

 

[doublespaces]

Like already mentioned, if you put the regulator before the fuel rail, you can't run a return off the fuel rail itself because no pressure will build up in it. Keep in mind, what you have in stock form is essentially the second picture but the return line is in the tank with the factory regulator.

Since you have PI, run the first setup, fpr after the PI rail on the return line. Your LPFPs will pressurize the entire line up to that point, and will begin to bleed off pressure depending on what setting your FPR is.

 

[pysical]

Yeah I forgot to draw the return line on the second picture. But after more research the dead head system isn't ideal for the PI as mentioned by martymil. I am going with the first version. Thanks

 

[NoGuru]

So the port injection only see's 72psi?
Trying to makes sense of putting the FPR after the PI rail.

 

[NoGuru]

I just realized since you are spraying into the intake it does not have the pressure needed like inside the cylinders. It's making sense now.