Fuel rails see a lot of exposure to radiated heat since they sit atop the engine, plus smaller 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. And hot gasoline hurts performance.
As the temperature of fuel increases, it becomes more vaporous, and in a closed system it can build 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, making the computer to pull timing out of the ignition system to eliminate the detonation, which reduces horsepower. Want to know what reduced ignition timing does to power output? Just one degree removed from the engine’s normal programmed timing can equal a loss of 10-12 horsepower!
Hot fuel also will not atomize as efficiently as cooler fuel. On fuel-injected engines, the fuel-injector spray pattern can be affected; specifically, how the fuel mixes with the air entering the cylinder, also robbing 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.
Heatshield Products developed the FR Shields™ to create an easy solution to this problem. FR Shields wrap around the fuel rails to shield them from the radiated heat in the engine compartment. Cooler fuel rails means less heat transferred from the rail to the fuel inside for more efficient temperatures and a properly functioning fuel-injection system.
We wanted to see just how much FR 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.
ABOVE: The first step was to drive the car, then take the readings of the uncovered fuel rails, 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.
ABOVE: The passenger-side fuel rail read 165 degrees F.
ABOVE: We had an extra set of FAST fuel rails to use in showing how to fit FR Shields to your setup. First, cut the material to the length of the fuel rail. Cutting and trimming are easy; you can use a pair of regular heavy scissors.
ABOVE: When measuring and marking for all the openings, don’t forget about a slit/hole for the fuel rail mounting tabs to pass through.
ABOVE: 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 FR Shields can be wrapped past the injector.
ABOVE: 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 material around them.
ABOVE: After the rails were reinstalled, we drove the car for the same amount of time as our baseline test. The driver-side fuel rail with the FR Shields on was 136.5 degrees F, down from 153.5 degrees F in our baseline—a drop of 17 degrees.
ABOVE: The passenger rail measured 123 degrees F, down from 165 degrees. That’s a drop of 42 degrees!
ABOVE: We had also mounted a probe inside both fuel rails to see what the temperatures were underneath the FR Shields. 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: 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 it will be to keep the fuel in your rails more than 20 degrees cooler when summer gets here!