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Returnless Fuel System - Operation

CSVT#49

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Joined
May 28, 2004
Messages
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Location
Andover, MN
I'm trying to figure out what all would need to be done to change over a return style fuel system to a returnless system.

So I found an old thread, which somewhat asked the same question I had, but not to the level of detail I had hoped. So I am starting a new one for search purposes...

It could be done, but it would require swapping in/out a number of other components to allow the fuel delivery to be controlled properly. Not something you could do in a weekend unless you had worked it all out and had all the correct parts on hand.

so... what components would be needed?

I'm trying to think through what all happens, is an open loop system?

-ECM turns on fuel pump
-fuel pump pumps fuel through line
-fuel reaches pressure regulator, which regulates incoming fuel to set pressure
-Returnless: ECM monitors fuel pressure regulator creating a closed loop and adjusts fuel pump output??
-ECM turns on injectors accordingly
-injector sprays fuel into cylinder
-Return: excess fuel cycles back to tank??

Reason why I ask is that my 2005 ST220 fuel rail is a returnless rail, but it has no electronic monitoring fuel pressure sensor like my 2005 Escape rail has on it. So I am wondering how the returnless system operates on the ST220 Mondeo. I am assuming it would be an open loop system since there is no feedback to the ECM regarding fuel pressure, which if this is the case then I don't see why a returnless fuel rail couldn't be swapped into a return style car. If this is true then all you would need to do (again making an assumption here) is remove the unused return line and plug the corresponding ports on the tank. This should not have any effect on the fuel pump as it only has an inlet and an outlet. The only thing that could potentially be effected is the output from the ECM to the fuel pump, however if the system is truly open loop and the ECM is not monitoring the fuel pressure regulator then there would be no change in the ECM output to the fuel pump anyway.

So that said... thoughts, comments?


EDIT: I just thought of this... unless the ECM is monitoring fuel pressure at the fuel pump, but this would not make sense as it would need to look at the pressure after the regulator where it matters...
 
I have always thought return was more ideal for higher hp applications. :shrug:

Only benefit that I could see from return vs returnless is the possibility that the fuel temperature could be cooler with that of a return style. Other then that... everything else would be the same I would think.
 
I'm sure someone will chime in, but i know for a fact that some Terminators owners convert to return, i believe SRT-4 owners too...
 
The difficulty here is that I need to use the returnless fuel rail regardless of whether it functions with the current system as a return style or if I convert the existing system to returnless. So if the benefits of a return style are in fact just cooler running fuel temps then I won't be completely capitalizing on that because the fuel rail I have to use is not built to operate that way and the fuel will not be flowing through it the same way it would with a return style fuel rail. I guess we'll see what someone with more experience chimes in with. Otherwise I'll bounce this question off some of the engineers on the engine team at work next week when I get back on the 5th.
 
why not just use the NPG fuel rail mod? it was designed to allow the use of the returnless fuel rail on return system cars. :shrug:
 
I know you'd like to use that rail and you still might be able to, but for your plans and power level I would only do return style.
-J
 
What's your opinion as to why the return system should be used?
Safer for big power IMO, thats why you rarely see the big HP cars run returnless, they are almost 100% return.
I like a mechanical regulator and more supply over electronic sensors calculating how much fuel I need when I drop the hammer. More reliablity with a return also, but I never had a problem with the FPRS in my '04 Cobra but lots of my friends did.
-J
 
Yes the more I think about this I am going to have to revamp the fuel delivery system a little more beyond just upgrading the fuel pump to the 255LPH version.

When I finish removing the engine, trans, and exhaust I'll siphon the tank and replace all of the lines and connections to allow it to support the monster I am creating.

Ugh... my April 30th deadline is coming up sooner then I would like with all of the little details I have not been planning for...
 
Glad thats cleared up. Don't worry about a deadline, at least you will have it done right and how you want it.

While we are on this topic i was curious, is the stock fuel pressure regulator sufficient enough for a 255lph pump?
 
I am not sure where you are going with this project but I ran over 500hp and I had more than enough fuel using the stock fuel lines.
 
I am not sure where you are going with this project but I ran over 500hp and I had more than enough fuel using the stock fuel lines.

I never knew you ran more then 500hp at the wheels? So Joey what did you run for a fuel pressure regulator, fuel rail, and fuel pump?
 
My 220 3.0 conversion has the newer returnless system rail, yet the 2.5 had the return system. I was told that the 220's ecu controls the fuel pump and hence the pump can run to suit the fuel required. The 2.5 fuel pump has a simple on or off function, so on the returnless rail it would just continually run building up the pressure.
When my engine was previously installed into a ST200, the return line was capped off and the feed line was connected directly to the rail. When running the fuel rail was seeing 8bar in pressure and the pump would scream when in use due it pumping continually. A friend has this setup in his 3.0 conversion and over time the fuel pump has burnt out.

The tuner who mapped my car stated that 8bar was to high and installed an additional regulator on the feed line which returned fuel down the existing return line. The pressure was then monitored at the rail on a rolling road and the additional regular adjusted to keep the pressure at the rail to approx 3.5-4bar, thus returning additional fuel to the tank. This method seems to be working well and the fuel pump runs continually but now has a return to ease the pressure and prolong the pumps life.
 
I am not sure where you are going with this project but I ran over 500hp and I had more than enough fuel using the stock fuel lines.

He has a returnless hence one line as is so he is going to have to add a line anyways. It's worth the extra few cents per foot at that point for a safeguard like that.
 
He has a returnless hence one line as is so he is going to have to add a line anyways. It's worth the extra few cents per foot at that point for a safeguard like that.

No... I have a 98 CSVT with a return system. I have both a 2005 Escape and ST220 fuel rail that are returnless. If the stock lines flow enough fuel to keep up with what I'm looking to do then I'll leave them. However I need to inspect the general conidtion of the lines before I make any decisions. However that said I bent new lines for my Camaro when I built that car and it wasnt' to bad at all. For the price I think I'd do it again for this car especially with the way our MN weather brings havoc to the underside of cars. I'll post the components I'll be using shortly in my build thread.
 
Oh I thought you had a 2000 based on the op, my bad. I guess it does say it in the sig, its the simple things that get by me. I plugged my feed use the stock return and added the -6an line. It's not going to hurt anything. When I go to part the car I am going to take the line off and save it for later and return it to the way it was. To each their own.
 
Oh I thought you had a 2000 based on the op, my bad. I guess it does say it in the sig, its the simple things that get by me. I plugged my feed use the stock return and added the -6an line. It's not going to hurt anything. When I go to part the car I am going to take the line off and save it for later and return it to the way it was. To each their own.

You could have looked at his signature :laugh:

I'm with them on the return style. :), you already have it...and you know it's working..don't create another issue or add more to your work load.
 
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