Do I need a fuel RETURN line???

[MandarinaRacing]

I was talking to a friend yesterday and he pointed out the I have my fuel system plumbed the wrong way.
The way is set right now, one of the outlets of the regulator is going to the carb, the other is going to the nitrous solenoid and plate.
He said that the fuel problems I 've been having are because the pressure cannot be managed while it's being dead headed against the carb and solenoid. He suggested installing a return line so that the excess pressure goes to the tank and then I can regulate it better.
Any comments?

Alex

 

[Asa]

it makes sense to me
you need to run more fuel when on the gas, but you currently have it setup so that it's running fine without the gas

i'd suggest looking at other cars with the giggle gas, find out what they did to get around that problem

 

[rbohm]

8) if you decide to run a return line, i suggest you plumb the fuel line to the nitrous fuel solenoid so that is recieves full fuel pressure from the pump, split the line before the regulator, then run your return line after the regulator. you can either run the return line to the suction side of the pump, not the best way but it works, or you can run the return line to the fuel tank, best way.

 

[65coupei6]

Yes, running a fuel return line is a good thing because it prevents cavitation. Here is a link which describes cavitation: http://www.mcnallyinstitute.com/01-html/1-3.html

Do as rbohm said. The easiest way is to run the return line just before the fuel pump. Or the best way is to run it back to the tank. To run it to the tank all you would need to do is drill a hole in the fuel filler neck that goes to the fuel tank and tap it there.

 

[Anonymous]

Pressure control valves may or may not need an outlet to dump excess flow out of the discharge piping. A pressure regulator senses the amount of flow on the down stream side and limits the amount of flow through the valve. Look at what happens when the pump is dead heading into closed valves. Some regulator valves can sense the downstream pressure, and when the pressure meets the set point, it can shut off the flow completely. Now when the solenoid or carb float opens, the regulator sees a drop in pressure and opens the valve up to provide more flow. In some cases, the valve could be relatively slow acting and your system may see insufficient flow and or could over correct and produce a surge in pressure. Some valves 3 ports, 2 outlets and one inlet. If present, One of the outlets usually dump back to a suction tank or suction side of the pump. This is a common arrangement on piston pump systems since you have to relieve the pressure or the pump will continue to build pressure and rupture the line.

That said, I have not set up a pressure regulator and NOS system on a car, so I do not know the configuration of the regulator valve. But I could see the advantage of a return line if the response of the valve is slow, or if openning the NOS solenoid causes a rapid change in pressure and flow requirements. Does your valve have 3 ports on it? If so, one is likely a return port.

I don't believe a return fuel line is going to do anything with regards to cavitation of the fuel pump. If fuel pump cavitation is a problem then you have a pump that is not properly designed for the system or you need to look for blockages at the suction side of the pump. Fuel pumps are designed to deadhead against closed float valves and solenoids.