Returnless EFI
 

I have a custom 13b install and I have the luxury in this install to design the fuel system any way I want. I’ve read a BUNCH about returnless EFI installs and they seem very interesting to me due to their lack of fuel return to the tank. I’ve designed one for my application in the attached PDF. Does anyone know of a significant reason why a proper returnless EFI design wouldn’t work in a 13b application? Thanks in advance for your reply.

-J

It looks like you need a one way valve on that system you are showing so that the pump doesn't decide to pump fuel in your return line.(at the return T).
I am not an expert but I am thinking that the injectors and fuel line would be pressurized with fuel all the time if it had no return line to the tank.

and thats different than normal?

Well, there isn´t single reason why it shouldn´t work as in any other application. Many people will tell you that it can´t be done but its just their excuse for lack of understanding and competence in given subject.

Maybe you´ve read bunch, but your diagram lacks many things of proper returnless system. Fuel rail pressure sensor and intake manifold pressure sensor are essential for controlling desired deltaP across the injectors and fuel pump speed controller is another essential component. Then of course you have to have capable ECU to control it.

There are many advantages, for example you can run very high rail pressures which promotes atomization with much lower power consumption everywhere as pump isn´t running at full speed as in return system and hot fuel isn´t returning to fuel tank, so its another benefit for pump, its better cooled and it pumps only so much what is needed in given situation.

You should read this, whole:) http://www.pistonheads.com/gassing/t...+control&mid=0

That guy apparently knows thing or two, and what he does holds probably more merit than opinion of every expert on internet:lol:

Returnless EFI design
 

Misterstyx69 … Yea … I too thought I’d put a check valve after the fuel cooler and BEFORE the return (aka returnless) T.

Liborek …. The application for this design is in a “smooth throttle” application. IOW, this application DOES NOT have to live in an environment where a gas pedal is constantly opening and closing. In my application, the throttle opens smoothly, stays in a position, moves smoothly if it is moved at all and …. When it’s time to close the throttle, closes smoothly. You might be thinking to yourself … “hey, that sounds like an airplane application” … and you’d be correct. I’m using Tracy Crook’s EC2 engine controller which is designed for aviation applications. One thing to note is that all of the listed pumps are outside the fuel tanks. Tracy’s controller has been used in a returnless design before but I wanted to run said returnless design by the experts here to get input on my parts selection. The advantages you mention are the EXACT advantages I want to exploit. This is because efficient fuel utilization = extra flight range at the same HP output. One thing I believe I WILL FOR SURE add is an impact fuel pump cut-off switch in case of an unfortunate off-field, uncontrolled, “smoking hole” resultant landing. All in all I think you’ve said I need a couple of more parts interface to my ECU and I should be good to go. S-W-E-E-T. Thanks for the help.

-J

pretty sure all you would need is a fuel pump, fpr, and the line to the rail. On some factory setups the fpr is on the line between the pump and the rail andd if one were to put a Y on the pressure side of the fpr it would bleed the extra pressure back to the tank. This is ok because the fuel has not yet reached the hot engine bay. So the line from the tank to the rail would be pressurized, add an fpr with a Y fitting on it with the return running back to the tank and dead-end the fuel rail and you have a returnless system. Some manufactures use this design but they have the fpr in the tank. But the setup I described and the manufactures setup are pretty much the same. I am going to dead end my system when I go e85. If I missed anything let me know. And I think what I described is alot easier to understand with the picture I have drawn. Also, I think only ford uses the fuel pressure sensor to pwm their pump but I may be wrong.

On the subject of the Fuel Pressure regulator, how does said device know at what fuel pressure it should keep the rails? I know the FPR gets vacuum input from the manifold to allow additional fuel in the rail during times of throttle advance (I’d pressing on the gas pedal) but other than that how does it know I want oh ... say .... 85PSI in the rails?

-J

there is usually an adjustment screw on the top or somewhere on the body of the regulator to set base psi.