Return-less To Return Style Fuel System Conversion

If your car has a returnees style fuel system and you’re trying to make big power, especially with a turbo or supercharger then you probably want to convert you car to a return style fuel system.

But first, how do you know if your car is return-less? Well besides searching online you can poke around under the car or in the engine bay and if you only have one line running from the fuel tank up the fuel rail then you have a return less system.

In a return-less system fuel pressure regulation is done inside the tank or by voltage going to the fuel pump. There may also be other electronics involved in a returnees system to adjust/maintain fuel pressure.

In a return style fuel system fuel pressure is regulated at the fuel rail or near it using a fuel pressure regulator. The fuel pressure regulator will bleed off excess fuel back to the gas tank using a return line that runs all the way back to the tank. So in a return style fuel system you have two lines running from the gas tank up to the engine bay.

No why would you want to convert from return-less to a return style? The main reason people do this conversion is so that you to manually set the fuel pressure instead of relying on the stock electronics inside the car or gas tank. This is helpful for high horsepower cars that far exceed what the manufacturer designed for. Also, if you add a turbo or supercharger to your car your combustion chamber becomes pressurized. This means that even though the fuel pressure might be regulated to 45psi the combustion chamber will be pressurized by boost. So if you are running 10 PSI of boost then your injectors will need to be pressurized an extra 10 PSI as well to effectively pump the fuel into the pressurized combustion chamber.

Luckily, most aftermarket fuel pressure regulators have a vacuum line on them that can be used to increase the fuel pressure as boost increase. This means at 10PSI your fuel pressure will also increase by 10PSI so that the fuel can be squirt the fuel into the pressurized combustion chamber.

Now that we understand the difference between the two systems and why you would want to do the conversion, let’s cover HOW to do the conversion. Most popular platforms will have a kit available. However, they can be very expensive. For example this kit for a mustang that is 2000 dollars. This kit for an RSX is 550 but it does not include a fuel pump hanger, fuel pump or fuel rail so add those items and you will be over 1k.

If you don’t want to buy an off the shelf kit its not complicated to modify your existing setup. The basic things you will need are:

1. Modified fuel pump hanger
2. Fuel lines
3. FPR
4. Fuel rail
5. Fuel filter

The most complicated step will be modifying the stock fuel pump hanger. You will need to find a way to add a fitting onto the hanger to return fuel to the tank. For example, drilling a hole and bolting a 90deg fitting onto the stock fuel pump hanger. You could also glue a fitting in place but bolting seems like the safest option.

Now we can move onto fuel lines, most people use AN lines. AN lines are the most durable and even though they are expensive they will last much longer and be much safer than rubber lines.

Once you have a feed and return line running up to your engine bay you should add a fuel filter at some point in the feed line to ensure no contaminants make it up to your fuel injectors or FPR.

In addition to a FPR you will also need a new fuel rail that has two ports on it. An entry port for the feed line to supply fuel and an exit port to run fuel to the FPR to bleed off excess fuel back to the gas tank.

Hope this helps explain the differences between the two systems. Check out some of my other fuel system videos!

свернуть