SCORE Journal - The Official Publication of SCORE Off-Road Racing
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include taking the fuel pumps to its drawing specification for flow, pressure, and amp draw." There are a multitude of fuel pumps that can be used in all types of race vehicles. The most important factor is to make sure that the fuel pump is up to the requirements of the engine. "In order to build out a proper system a team needs to know three things that include, the type of application which can be off-road long-short course, the size and type of motor (V6, direct injection or carb, EFI, etc.), and the expected horsepower at the flywheel," says Harmon. "Most OE pumps aren't made to handle the heat and jumps of off-road races or the variable pressure of a turbo, whereas aftermarket pumps are generally tougher and can handle the vibrations, heat, and variable pressures in most types of racing. Identifying the size of the motor establishes whether one needs a pump capable of supporting high horsepower, high volume, or both. Finally, the horsepower rating at the flywheel is a common way of establishing which pumps can support the estimated demand of the motor." In order to find out how much fuel actually needs to be delivered to the engine, is often a decision that comes from the engine builder, who has tested the engine on the dyno and can give teams the proper numbers for meeting those requirements. "Calculations to determine exactly how much fuel the engine will need are available online but usually require a dyno test to determine an accurate horsepower and BSFC (Brake Specific Fuel Consumption) rating," says Harmon. "From there, an exact flow@pressure can be established and a specific pump can be identified. Since this is a bit more involved than most teams wish to get, fuel cell manufacturers like us, offer a handful of systems to fit nearly every application based on a rough horsepower rating. Pumps from Aeromotive and Weldon are our best sellers and handle everything from 100-1,100HP applications." Heat can also be a contributing factor in achieving proper fuel delivery, as desert racing environments are extremely hot, and when combined with the heat generated from engines, shocks, exhaust systems and more, there's always a possibility that fuel can boil and cause other problems. "There are a few fuel cell manufacturers that are installing inline fuel pumps inside of the cell," says Craig. "This is done to get the pump as close as possible to the fuel supply to minimize vapor locking -- among other reasons. If the fuel begins to vaporize or boil, fuel delivery and pressure begin to fluctuate, resulting in poor engine performance and potentially the pump vapor locking. If this happens, the pump might not be able to overcome this situation until the fuel cools. This also occurs when the vehicle is subjected to elevation, such as in a Vegas to Reno run." This is one of the reasons why many race teams prefer to run fuel pumps submerged inside fuel cells. "Fuel pumps are inherently designed to push fuel," says Torvik from Fuel Safe. "Running your pumps in the tank will allow them to last longer. Pumps run cooler when they are in the tank because they are pushing fuel, as they are designed to do. This way, they have less chance of producing a vacuum or experiencing cavitation." But according to Craig at Weldon, this doesn't always solve the problem. "Putting the pump inside of the fuel tank does not necessarily keep the pump cool, as it will be as hot as the fluid that surrounds it," says Craig. "Ideally, you want to size the fuel pump to be as close as possible to the engine's actual consumption rate, to balance the amount of "excess" fuel flowing through the system. This is usually a good way to try to keep that heat out of the fuel in the cell." Mistakes Remain Hidden Until It's Too Late According to both these experts, teams will ultimately use what works best for them, but that can sometimes lead to some common mistakes in the vehicle's fuel delivery system. "Some common issues that we see are venting, fuel pump, and maintenance issues," says Torvik. "Quick fueling is a top priority, especially in the off-road market. Our dump cans give you the ability to fill 10 gallons in less than eight seconds. When fueling this quickly, you need a vent that can keep up. If you don't have a proper vent size for your fueling application, the fuel will come 077 SCORE JOURNAL