I have an existing 6mm copper fuel pipe in my car and I'm in the process of upgrading to fuel injection and I will be fitting a new 8mm high pressure pipe for the fuel feed and thinking of using this existing pipe as the return to tank.

Is 6mm a suitable diameter for using as a return for the new fuel injection set up?

Cheers

Rob

are you running an fpr at all?

if FPR is Fuel Pressure Reg then Yes. Just after the fuel rail.

6mm is fine for a return line.

6mm will be fine. thats what im using!

If you're overloading a 6mm pipe on fuel return, you need to use the loud pedal more!

I used a 10mm pipe as return to stop it interfering with the pressure regulator.

Same diameter as your FPR feed pipe would be suitable.