How to Keep Fuel Rails Cooler and Make More Power with FR Shields

At Heatshield Products, we’re big proponents of automotive heat shields and fuel line insulation. Fuel rails see a lot of exposure to radiated heat since they sit atop the engine, plus small engine compartments mean less airflow to help move heat out. Lower-profile hood lines and factory engine covers on modern cars can also trap heat, despite composite intakes, aluminum heads, and aluminum blocks that dissipate heat faster. This leads to increased fuel temperatures, and hot gasoline hurts performance.

Without a car heat shield, the temperature of fuel increases causing it to become more vaporous. In a closed system, that can create pressure that will cause fuel-flow irregularities, especially within the fuel rails. Hotter fuel is also less dense, so not as much fuel charge can be delivered to the cylinders causing a potential lean issue that leads to detonation and decreased horsepower. Just one degree removed from the engine’s normal programmed timing can equal a loss of 10-12 horsepower!

Fuel line insulation is also important because hot fuel also will not atomize as efficiently as cooler fuel. On fuel-injected engines, the fuel injector spray pattern and how the fuel mixes with the air entering the cylinder can be affected, robbing your vehicle of valuable horsepower. Larger aftermarket aluminum fuel rails are susceptible to these issues, too, especially in boosted applications where a turbo or supercharger contributes to the amount of heat the fuel rails are exposed to.

So how do you keep your fuel lines cool and save your vehicle’s performance? Heatshield Products developed our patented FR Fuel Rail Heat Shields™ to create an easy solution to this problem. Our fuel line insulation wraps around the fuel rails to shield them from the radiated heat in the engine compartment. Cooler fuel rails mean less heat transferred from the rail to the fuel inside and more efficient temperatures for a properly functioning fuel-injection system.

We wanted to see just how much our FR fuel line insulation shields improve performance, so we took a 2013 Camaro SS with an LS3 that had been modified with a heads/cam/long tube headers package from Trick Flow Specialties, as well as an LSX Intake, fuel rails, and injectors from FAST. At the wheels, the car made about 490 horsepower.

The first step to figuring out how to keep these fuel lines cool was to drive the car then take the readings of the fuel rails without fuel line insulation, including a temp reading within two minutes of parking to ensure non-running heat soak would not be a factor in the results. The driver-side fuel rail measured 153.5 degrees F while the passenger-side fuel rail read 165 degrees F.

We had an extra set of FAST fuel rails to use in showing how to fit FR Shields to your setup. First, cut the fuel line insulation to the length of the fuel rail. Cutting and trimming are easy; you can use a pair of regular heavy scissors. When measuring and marking for all the openings, however, don’t forget about a hole for the fuel rail mounting tabs to pass through.

You have two options for the injectors: mark and cut holes for with an Exacto knife or use scissors to create a flap of sorts so the heat shield sleeving can be wrapped past the injector.

We left the fuel injectors connected to the fuel rail so that we wouldn’t have gas going everywhere. The injectors inserted into the holes in the FR Shields, and we then wrapped the fuel line insulation around them. Included with the FR Shields is our specially formulated high-temp Thermaflect Heat Tape™ to secure them on the rails and seal the seams.

After the rails were reinstalled, we drove the car for the same amount of time as our baseline test to see how well the FR shield kept the fuel lines cool. The driver-side fuel rail with the FR fuel line insulation on was 136.5 degrees F, down from 153.5 degrees F in our baseline—a drop of 17 degrees. The passenger rail measured 123 degrees F, down from 165 degrees. That’s a drop of 42 degrees!

We had also mounted a probe inside both fuel rails to see what the temperatures were underneath the fuel line insulation. We measured 139 degrees F on the passenger rail (was 165 degrees baseline) and 133 degrees F on the driver rail (was 153.5 degrees F baseline). This gave us our true difference and measure of how these shields keep your fuel lines cool: a temp drop of 26 degrees F on the passenger fuel rail and 20.5 degrees F on the driver rail. Now, imagine how simple fuel line sleeves will make keeping the fuel in your rails more than 20 degrees cooler when summer comes!