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04 GTO LS1 fuel system

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  • 04 GTO LS1 fuel system

    My 04 GTO LS1 engine seems to only have only a fuel feed line and no return. Am I missing something on the purchase of the engine or is this a new way to run these engines? Where does the excess fuel pumped to the engine go? I always assumed that a return line was necessary. Has anyone got any info on this matter?
    Thanks,
    Peter

  • #2
    Re: 04 GTO LS1 fuel system

    returnless fuel system i think they change pressure by changing pump speed? not sure though there is no returnline

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    • #3
      Re: 04 GTO LS1 fuel system

      Its called a returnless fuel system. Its an emissions thing that reduces fuel vapor load on the charcoal canister by not returning aerated and slightly warmer fuel to the tank and creating more fumes. The fuel pressure is controlled by a Pulse Wave Modulated fuelpump in the tank. Corvette's up to a certain point used the return style system and I'm sure there are aftermarket rails and regulators to go back to it.
      Central TEXAS Sleeper
      USAF Physicist

      ROA# 9790

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      • #4
        Re: 04 GTO LS1 fuel system

        Ok, Good information. But, I don't want to have to change the rails (budget restraints) and I can't utilized the stock tank fuel pump in my Studebaker. Is it possible to use an Aeromotive pump (which I purchased) with the stock hardware and make it work properly? If not, what is the least expensive path to operation?
        Thanks for the relpies.
        Peter

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        • #5
          Re: 04 GTO LS1 fuel system

          Originally posted by CTX-SLPR
          Its called a returnless fuel system. Its an emissions thing that reduces fuel vapor load on the charcoal canister by not returning aerated and slightly warmer fuel to the tank and creating more fumes. The fuel pressure is controlled by a Pulse Wave Modulated fuelpump in the tank. Corvette's up to a certain point used the return style system and I'm sure there are aftermarket rails and regulators to go back to it.

          I think you are describing the Ford system? The LS1 system I am used to, runs a constant pump speed with a regulator, and a retuyrn that's still in the tank, instead of the PWM version. at least I know that's how the trucks work.... f-bodies and gtos might be different?
          www.realtuners.com - catch the RealTuners Radio Podcast on Youtube, Facebook, iTunes, and anywhere else podcasts are distributed!

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          • #6
            Re: 04 GTO LS1 fuel system

            That's the info that I am looking for. If I change the whole fuel system to a "return to the tank style", I am sure that I will have to drastically reprogramme the ECM. At this point I just want to get the engine fired "stock" and work out the bugs in the car before I start tuning for power and performance. I really need some direction in this matter!
            Peter

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            • #7
              Re: 04 GTO LS1 fuel system

              GTO's, F-bodies, Corvettes, and probably the CTS-V. Cars have different emmissions standards than trucks. Might be a good idea if you have the hood clearance to run a truck intake and rails.
              Central TEXAS Sleeper
              USAF Physicist

              ROA# 9790

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              • #8
                Re: 04 GTO LS1 fuel system

                The GM units just use a pump with the regulator on the in-tank unit.
                You may be able to find the unit and modify your tank to fit it. The bad news is, I've only seen Bosch units and they're usually above $500 new. Sometimes as high as 800. Although there may be Carter units out by now.

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                • #9
                  Re: 04 GTO LS1 fuel system

                  either way, you CAN easily run a return system and just set it at the same pressure as the factory system. I am quite sure now that even the cars are not PWM, that's a Ford-only thing. On the GM cars, they run at a constant pressure always. It's no different than a return system other than the return is back at the tank, and the fuel line itself is one long deadhead.

                  What all is done to the engine combo? how are you tuning it? "Green Junk" on here has a lot of experience on these exact cars, we should try to get his attention here.

                  -scott
                  www.realtuners.com - catch the RealTuners Radio Podcast on Youtube, Facebook, iTunes, and anywhere else podcasts are distributed!

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                  • #10
                    Re: 04 GTO LS1 fuel system

                    I swear the FWD L32 Supercharged motors are PWM pumps and like a fool I extended that out to the other returnless fuel system GM cars. I knew the Fords were PWM because it was the reason they hadn't offered a supercharger kit for the 4.6L SOHC in the 03+ Panthers yet.
                    Central TEXAS Sleeper
                    USAF Physicist

                    ROA# 9790

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                    • #11
                      Re: 04 GTO LS1 fuel system

                      if you have to run a return line with your pump setup. just T it off just after the fuel filter like they do on an f-body. That little cylinder on the fuel rail is a pressure damper that is in theory supposed to keep pressures in check if you get a short surge. the '04 gto is different than the '05 plus as far as design. But i know that will definetly work on an '04.

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                      • #12
                        Re: 04 GTO LS1 fuel system

                        They stopped using full return systems on ls series engines in '98. Also if your in tank pump does not require a return you're ok. Assuming its internally regulated to 60-65psi which is the constant pressure of an ls1 fuel system. If you're using a stock gm computer that is the neccesary fuel pressure you'll need to make the tune work. if you're using and aftemarket computer setup with a stock motor, 45-50 will be plenty seeing as you're going to have to tune for it anyways. As soon as you put a cam in it though you'll need 60psi for the injectors to keep up with the increased air flow. If you want any good info on parts to hop that sucker up let me know I can point you in the right direction

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                        • #13
                          Re: 04 GTO LS1 fuel system

                          I've run 'em on the dyno with the stock ECU and just add a return system to make my life easy. This one we swapped out the heads, cam, intake, & added headers, made 515 hp. All the rest of the engine was stock.


                          There are very few people in this world who's opinion I value, you are not one of them.

                          300 in 1999

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                          • #14
                            Re: 04 GTO LS1 fuel system

                            Hey Guys, Thanks,
                            Again more good info. I am running an Aeromotive pump on my stock engine except for headers and cowl induction for now. The concept of a return from ahead of the fuel pump is intriguing, but I think, for future considerations, I should tap into the fuel rail and bring the fuel back from the engine itself as someone suggested. I can modify the end of the right hand rail quite easily. If I go that way, is that the only modification to the supply system that is necessary? Is the stock fuel regulator/damper sufficient? I am planning on having Howell reprogramme my computer unless someone has a better (meaning cheaper and easier) way of doing it. The car will be driven on the street and raced at Maxton. I plan on following Dutweiller's lead with my engine, although Dave seems to have somewhat of a handle on making these LS1's go fast. Any info is much appreciated. I was going to take my computer to Howell in March, but will hold off if someone can give me better advice.
                            Thanks,
                            Peter

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                            • #15
                              Re: 04 GTO LS1 fuel system

                              where are you located. I can set you up with a guy here in raleigh which is only 1.5 hrs from maxton if you want to do it before the april race. The piece on the rail is not a regulator, its merely a damper, whatever the hell that means, you still need a regulator. But as I said a full return is not neccesary with this system. if you can get the tanke to pressurize with a return line just after the pressure side of the pump you're good to go.

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