Re-using OEM fuel lines for swap - How does it work?

[Samwise_4k86]

Hi all!



Before I crack in to my engine swap later this year i'm hoping to do some reconnaissance since recently seeing that people are often re-using the 1st and 3rd Fuel lines and T'ing them together in to the Fuel Rail (Of an LS3 in this case)


It's awesome to see it's as "simple" as that but I really want to understand why exactly it's so effective before simply copying the solution and not understanding why it works out as well as it does.


So I was really looking for a bit of an explaination as to how the OEM fuel system works and what's changed in it for an LS swap for example.
I previously thought that the car's port injection and direct injection systems were pretty much seperate with different fuel pumps and lines for each but I found out recently it actually appear to "T" out from the singular pump/fuel tank and then heads up to the 2 seperate sets of injectors in the engine bay, so essentially by T'ing them back together you're just rejoining them to essentially make it 1 large line that copes with the fuel demands of an LS, etc?


In that case do you need to change the OEM fuel pump for an LS3 aiming to currently keep stock injectors and aim for roughly 500ish hp? on UK 99 octane (equivalent to 94 in the US i think, we don't get e85 over here at all). Or perhaps you upgrade the fuel pump, T the lines together in the bay and away you go?




Correct me all you like! Really looking to learn as much as possible here

[Ashikabi]

Just T them back together or cap one completely. Upgrade fuel pump in tank. Google"fuel pump calculator" to see how big of a pump you need. You can run a return-less system, just like stock. Fuel pressure regulator is handled by the BRZ in the fuel pump basket. If you're going to be racing I recommend you get the SAVAGE! Autoworks fuel starvation flap to install while you're replacing the pump. Effectively turns your pump basket into a surge tank

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[TRS]

For an LS, if not supercharged or hardcore NA mod or running on nitro, just T them.

For the FA20, you have two fuel lines. One for the Port injection and one for the direct Injection. But both are comming from the OEM fuel pump and are also Td there. With other words, T them to have twice the diameter of fuel line. This, with the OEM fuel pump, is enough even for a LS and even for a LS with a mild NA mod.

If you go for any kind of FI or nitro, you should consider bigger change in the fuel system. But for NA swap just stay with the OEM pump and maybe add a fuel trap door for mild track racing if this is what you are planing.

For anything serious motorsport style or FI topics bigger changes are needed. Then I would recommend much different mods.