Return vs. Returnless Fuel System Pro's and Cons

eabrillon1978 · Jun 6, 2012

Could anyone explain the pro's and con's of the return and returnless systems.

Just recently installed my dual pump setup using the factory regulator. Wondering if any of the gen II's came with a return system.

I haven't experienced any issues as of yet, but wanted to get some info on this in case I decide to upgrade the fuel system further, if need be.

I've read that the returnless system will keep the fuel cooler in the tank because it doesn't get routed through the engine. If so, isn't this what you want?

I'm running a Roe. What's the best way to route this if a return is the the way to go?

Is a AFR really necessary or is the purpose of having it due to the small size of the factory regulator and just a need for increased fuel line size?

Any help on this would be appreciated.
Eugene Brillon

1TONY1 · Jun 6, 2012

We know you cannot regulate after the fuel rails because you cannot come out the back end of the rail. Mine regulated before it went into the rails when the Roe was on.
I know that does not address the question

Allan · Jun 6, 2012

Returnless systems seem to be the latest design trend regardless of make or model in the last few years. Even though there is a performance benefit from not cycling the fuel constantly through a hot fuel rail and returning it to the tank, the primary reason for the trend is better control of evaporative emissions. Warm fuel is less predictable and less consistant for evap monitor self diagnostics, and the EPA mandates are getting stricter with each model year.

happy56 · Jun 6, 2012

On our race cars we run returns because it is easier on the fuel pumps

Tom86ZT · Jun 6, 2012

Could always add a cooler on the return.....

When you get into multiple pumps or higher pressure you almost have to have a return style..

Think of it this way, you are in a boosted car, 2-3pumps are running to keep the pressure at 65psi (or whatever) for the 150lbs injectors and 30psi of boost at 6500rpm....now you let off gas, where does the fuel and pressure for the fuel that is already in the line go? With a return you can "bleed" that pressure back to the tank through the regulator to the return line and it doesn't all get pushed back at the pumps. Much like a BOV on a boosted cars intake.

eabrillon1978 · Jun 7, 2012

Tom86ZT said:
Could always add a cooler on the return.....

When you get into multiple pumps or higher pressure you almost have to have a return style..

Think of it this way, you are in a boosted car, 2-3pumps are running to keep the pressure at 65psi (or whatever) for the 150lbs injectors and 30psi of boost at 6500rpm....now you let off gas, where does the fuel and pressure for the fuel that is already in the line go? With a return you can "bleed" that pressure back to the tank through the regulator to the return line and it doesn't all get pushed back at the pumps. Much like a BOV on a boosted cars intake.

Thanks for the explanation... Makes perfect sense.

Return vs. Returnless Fuel System Pro's and Cons

eabrillon1978

Viper Owner

1TONY1

Enthusiast

Allan

Enthusiast

happy56

Enthusiast

Tom86ZT

Enthusiast

eabrillon1978

Viper Owner

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