Return or Returnless Fuel System (LS3)

[Dan Carter]

Does anyone have a diagram of a return or return-less fuel system they built using an LS3?

The more I read the more confused I got. The OEM fuel rails seem to be return-less, so I am not sure how to route the fuel system.

One pump, two pumps, regulator sequence.....I think I know where the filters need to be......sure......

Help needed.

 

[Scott Rowland]

Stock fuel rails will be returnless. You can use them, but unless you use the stock type intank pump that has an integral pressure regulator, you will need to put an aftermarket pressure regulator by the rails with a return line.
Or, start from scratch with new fuel rails and plumb it correctly (imo) with a regulator by the fuel rails and return line. I always do dual feed (feed each rail) and dual out to the regulator and single return line. That way you don't run a chance of a differential pressure from the furthest injector.

If that still makes no sense, you could find a ton of diagrams online.

 

[PeteB]

I'd call it a semi-returnless system. The fuel pressure regulator goes between the fuel pump and the fuel rail, not after the fuel rail, so it's a "returnless" system. However, the FPR has a return line to the tank, so excess fuel is returned.

The standard setup on a SLC is, from the tank: fuel filter, lift pump, surge tank, fuel pump, filter/regulator with return line, fuel rail. The surge tank also has a return line to the main tank.

 

[PeteB]

Stock fuel rails will be returnless. You can use them, but unless you use the stock type intank pump that has an integral pressure regulator, you will need to put an aftermarket pressure regulator by the rails with a return line.
Or, start from scratch with new fuel rails and plumb it correctly (imo) with a regulator by the fuel rails and return line. I always do dual feed (feed each rail) and dual out to the regulator and single return line. That way you don't run a chance of a differential pressure from the furthest injector.

If that still makes no sense, you could find a ton of diagrams online.

C6 Corvette uses an in-line filter/regulator between the tank and the fuel rail.

 

[Dan Carter]

Pete/Scott thanks excellent explanations....that's the diagram I drew for myself then got confused by my "research"....I considered using the Aeromotive Phantom in tank fuel pump system, but I really need to keep this build simple. What brand external fuel pumps did you use?

 

[PeteB]

I used a Carter pump for the low pressure lift pump and a Walbro pump for the high pressure feed to the engine.

 

[Dan Carter]

Ok. Heading to Summit in the AM to "requisition" parts. Decided to use PTFE hose after reading a lot about new gas additives and impacts of oxidizing fuel due to the return cycle in this layout. Ideally I would do it all in metal. Build a bread board duplicating the space and bend it all out. A bit labor intensive, but never any doubt.

Thanks:idea:

 

[Scott Rowland]

I run a s.s. filter insert first in tank, then to a holley black lift pump (140g an hour) to a surge tank, then off to a Holley twin f.i. pump (140g an hour at 50psi [1200 hp]), then to a large 30 micron filter. A single -8 going to a Y with dual -6. Then into each rail, back out dual -6 and to the pressure regulator. From there I come back to the surge tank, then at the top of the surge tank, a line back to the tank. I also installed a roll over/ check ball vent in the tank itself.
The pumps are very quite. The Holley dominator twin pump can be wired separately so you only use one pump until you start reaching boost, then the second kicks on. This way you don't get nearly as much heating of the gas just passing through the hot rails and back to the surge tank, again, and again, and again. Over kill though unless going forced induction.

 

[Dan Carter]

Scott. I don't have the car yet....2 more weeks....so no tank to visualize with......what hole/access point did you use to secure the filter? Did you use the OEM fuel rail as a start? Did it have schradder valves on one end to remove/tap into as an exit point? I'm intrigued by your setup.

 

[Troy Truglio]

I am going to use this system and it is returnless with the walbro 262 pump for the surge and will use a 190 inline walbro for the feed with inline filters. I am not running an LS, but I would think you could adapt this up. It is nice, but costly.

https://www.radiumauto.com/FST-R-Fuel-Surge-Tank-with-Integrated-FPR-P348.aspx

 

[Dan Carter]

That radium system is very clean. Thanks for the heads up.

 

[Will Campbell]

The factory sells a complete fuel system- hoses, pumps, filters, reg, surge tank, etc for those who don't want to re-invent the wheel. Unless you have special requirements like mondo power, the optional facotry kit is very easy to install, and proven in many installations.

 

[Scott Rowland]

Scott. I don't have the car yet....2 more weeks....so no tank to visualize with......what hole/access point did you use to secure the filter? Did you use the OEM fuel rail as a start? Did it have schradder valves on one end to remove/tap into as an exit point? I'm intrigued by your setup.

I am running a 1uz motor with twin turbos, so my rails are custom also. I have "looped" stock fuel rails though by welding fittings on the ends and making a crossover to equalize fuel pressure better. And also made returnless fuel rails into a return style by cutting ends off and welding fittings on. Most stock rails will be plated steel or s.s., so not hard to do.
Typically, having the regulator so far away from the rails can create unreliable fuel pressures and a dip in pressure right when you mash on it. Fine for a stock car or moderate power gains, but you don't want the pressure to drop or be inconsistent when you have your foot pegged making 700hp. Especially injector to injector pressure differences. That's why I always feed both rails, and exit both rails and keep pressure regulator as close as possible to rail exits.

 

[Scott Davis]

I choose to change from stock "returnless" system for the same reason as Scott..only I'm not going to have near 700hp but with E85 you need to flow 30% more fuel. If you're thinking about that as an option consider changing. Everybody and their mom makes an aftermarket billet fuel rails these days and good ones can be had for relatively cheap (unless you have a 1uz apparently...ouch) and most are set up for return already.

 

[Dan Carter]

My precedence here is the GM design for the LS3 480 engine....it is a return-less system (mostly). I have an LS2 Corvette which is return-less (pump and regulator in the tank I believe). The car gives me everything I need. I have to believe that imitating that flow pattern as much as possible (RCR tank allowing of course) will not require (if any) mods to the GM ECM unit I bought with the engine as well. I do not want more power (480 is enough for me), but reliability is critical. I think I will go to stainless steel lines for longevity, but it will take some careful work, good planning, good tools and patients to build it.

Hope the car gets here soon....I'm ready to dig in.

 

[Troy Truglio]

I am running a 1uz motor with twin turbos, so my rails are custom also. I have "looped" stock fuel rails though by welding fittings on the ends and making a crossover to equalize fuel pressure better. And also made returnless fuel rails into a return style by cutting ends off and welding fittings on. Most stock rails will be plated steel or s.s., so not hard to do.
Typically, having the regulator so far away from the rails can create unreliable fuel pressures and a dip in pressure right when you mash on it. Fine for a stock car or moderate power gains, but you don't want the pressure to drop or be inconsistent when you have your foot pegged making 700hp. Especially injector to injector pressure differences. That's why I always feed both rails, and exit both rails and keep pressure regulator as close as possible to rail exits.

I will have a similar system as yours with a 1uzfe TT. I plan to run like 10-11psi (maybe 450-550rwhp) now on the stock internals and later bump it up to like 15-17psi (maybe 600-650rwhp) and rev to like 9000+.

So for me I plan to make some custom larger rails and run 1000cc injectors to have room to expand. I was going to have the main line off the radium setup and split before the rails and have one go into each. On the end of the rails I was going to have them go back to each other to make sure they balance out fully. I think this keeps it simple and will do what is needed. I am thinking I want a system that will handle the load for now and later without swapping things and only have to build up my internals (con rods, arps, cams, shimless buckets, valve springs, port and polish). Then just turn that boost up a bit.

I think the returnless system can work fine up to a certain hp level, maybe 700 or so and that is when the pump gets limited so maybe the dual pump setup or something like that.

 

[Scott Rowland]

Hey Troy. Couldn't help but notice you are gonna run a full sequential trans. What model is it?

 

[Troy Truglio]

Hey Troy. Couldn't help but notice you are gonna run a full sequential trans. What model is it?

Quaife full seq 6spd

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