So people usually use the stock return line for fuel supply when upgrading and they have to remove the stock fuel source line and put in a totally new return.

I was wondering if it were possible to have a returnless system with the FPR back by the pump.

I've read on power steering systems, when the pressure is not needed/too great, the pump internally bypasses so that it just circulates the fluid inside itself and the impeller effectively moves nothing. This theory shouldn't be too hard to translate over to a fuel system, should it?

 

There are a few aftermarket pumps that run in cyles, as needed. The downside to this design is the pressure can fluctuate, and the pump's life is not as long, due to stopping/starting.
I don't know of any pumps that actually bypass internally, but they may exist.
The idea of putting a FPR closer to the tank, and running the return from there has one disadvantage. It would be a little harder to access, in the event it needed adjusted.

 

Carb or EFI?

Most carb systems are returnless. Return-type carb setups are just to prevent vapor lock, unlikely in an electric pump setup anyway. (You always want the regulator as close as possible to the carb!)

EFI, lots of new cars have returnless systems where the regulator is in the pump assembly or the pump is pulsewidth modulated by the computer and there's no regulator (yikes!). It's purely an emissions thing, to keep the fuel from getting hot from circulating through the engine bay, and thus evaporate faster and contribute to evaporative pollution.

 

I was gonna say, my RX-7 (was) and my Toyota are both running Carter pumps with Holley regulators and no return lines, lol. Theyre both carbed with Webers though too, lol

~T.J.

 

You're right that they bypass, but they normall go back to the fuel tank. Normally this is an in-tank pump. If you look at pump dynamics, a vane pump is a positive displacement pump. It will pump a fixed amount of liquid or gas per cycle. If you don't have a bypass you'll blow something up. If the bypass goes from the discharge side to the suction side, the fluid and pump have a tendency to overheat. This is not a good thing in your case.

When I ran my Holley from RB, it had no return line. The thing that keeps them from not overheating is you will be using fuel, so the "hot" fuel will move out of the pump relatively quickly, so overheating isn't much of a concern.

I personally like return systems. It gives the tank a chance to mix up the 2 cycle oil.

 

I'll hazard a guess that the biggest differece between the power steering system and a fuel delivery system's location of pressure regulator is that fuel can vaporize and also compress. (?)

 

Ah, there's another thing. I'd never run premix as my primary seal lube system.

 

I was forced into premixing and now I think I'm starting to like it. It's on an EFI system with a return line. Yes, I'm sure the 2 cycle oil is getting mixed nicely.

 

OMP never worked, so Premix I must!

 

I like the OMP with an adapter plate and seperate reservoir idea.

I can patch a float into the unused "Windshield washer fluid low" light. Seeing as how my WIndshield washer reservoir doesnt have a level switch anymore. (I needed a larger one in my truck to get more mud off the windshield and I thought I could do with a smaller one in the 7 for weight savings... Not surprisingly, they were both compatible, so I swapped em. The truck one didn't have a level sensor though.)

It's nice having compatible vehicles. Batteries can be fenagled (reverse cables) to work in eachother. The truck uses an S5 RX-7 alternator... Little crap like that.