Information About Changing To A Twin Entry Fuel Rail

Fuel Rail Fittings

Assembled Fuel Rail

  Click on any of the pictures to view a higher resolution picture


I do not in any way take credit for the idea, or design, of the above twin entry fuel rail modification to the 3S-GTE. The above design has been around for a long time. I'm still not a 100% sure the twin entry fuel rail is necessary, BUT there are some interesting test results that I have seen showing problems with a combination of larger injectors, stronger fuel pump, and higher fuel pressure, all of which are part of my current setup. Either way, I figured it couldn't hurt, and since I had been chasing a fuel pressure problem, I decided to go ahead and perform the modification.

One difference between my mod and others is the exit from the fuel rail. While, like others, I use the cold start injector location as the exit**, I did not drill out the exit to accept a 12 mm x 1.25 adapter. Using such a large size, means the walls of the rail become thin, to thin in my humble opinion. Instead I drilled and tapped a female port for a 1/8 NPT fitting.

** on other rails the cold start injector is included in the design, but I no longer use the cold start injector, as I am using an Autronic SMC programmable ECU. You can find info on my Autronic install here.

Parts Required:

Note: I use a Malpassi fuel pressure regulator which has 1/8 NPT ports. Obviously if you are using a different regulator, you may need different  adapters.

1                925106    -6 AN TEE
2                991945    12 mm x 1.25 to -6 AN adapter
2                800106    Auto-Fit -6 hose end
1                849091    Swivel-Seal 90º -6 AN to 12 mm x 1.25 adapter
1                306006    Earl's Auto-Flex Stainless Steel Braided Hose - AN Size: -06 (3/8''); 6' Foot Length
2                824562    Swivel-Seal 45º Pipe Thread (1/8 NPT) to -6 AN*
1                806106    60º -6 AN Swivel Seal Hose End


Caution: Do not attempt this modification if you don't have adequate skills. Fuel is dangerous and highly flammable. Fuel injection systems run at high fuel pressures, so leaks, or failure of any part can lead to fire, injury, and/or loss of life. I am not an automotive engineer, and as such if you choose to use any of the information here, you will be doing so of your own free will, knowing that I make no guarantees about the accuracy or safety of any procedure or part.

Earl's web site offers instructions on connecting the fitting to the hoses. They can be downloaded from the following web page  I did not follow the recommended method of using a hacksaw to cut the steel braided hose. Instead I used a Dremel with a cutting wheel. I got that idea from another web site, but I lost the web address info. If the author happens to read this...then thanks for idea. Instead of masking tape I used electrical tape to wrap the hose before cutting. In any case here are some simple tips:

Order more hose than you need, so you can practice cutting the hose and attaching the fitting.
Always wear eye protection when cutting the hose, or doing any work, with a high speed rotary device like a Dremel.
Be careful handling the hose as the cut braided strands are very sharp and they can easily pierce the skin.
Always clean your completed hose assembly thoroughly.
Always test the integrity of your assembly for leaks.

This page was created by Dennis Heath.
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Please note that I am not a mechanic by trade, and that any information offered on this web page is free and without guarantee. Should you choose to perform any of the procedures listed on this site, you will be doing so of your own free will, and I will not be held responsible or liable for any damages that might occur from using information obtained here.