Weldon Fuel Pump - Let It Flow

Taking The Mystery Out Of EFI Pumps

Bob Mehlhoff Jan 19, 2007 0 Comment(s)

Today's high-tech musclecar is fed with an EFI system that helps create the ultimate performance car. With everyday combinations allowing more power, the ordinary EFI fuel system has proven very flexible. But whether your ride is a fourth-gen Camaro with modified factory equipment or a '65 Chevelle with an aftermarket EFI system, being able to fuel your motor correctly is critical to performance. Among the benefits a good EFI system provides are a big torque curve, easier starting, and improved fuel distribution at part-throttle.

To do this well an EFI system demands proper fuel pressure, adequate fuel supply, sufficient voltage, and free-flowing fuel lines and fittings. This month we're looking at the general requirements unique to an EFI system. Overlook one of these steps when building or maintaining your fuel system and chances are you won't be taking full advantage of your available horsepower.

Pump You Up
It takes fuel to make power, and to move fuel from the tank to the engine requires a pump. A fuel pump does not produce fuel pressure but produces fuel flow. Consequently, as a fuel system's pressure goes up, the fuel pump's volume will go down. On a modern EFI system, a bypass regulator-correctly matched for a given flow volume-establishes a controlled restriction.

Before selecting a fuel pump you'll need to know how much power you'll be making and the amount of fuel required to support it. This is best done on a dyno, but if this is not possible, make an estimate on the high side. Don't forget to add horsepower to your figure for supercharged applications. You'll also need to know the available voltage at the pump under engine load and the pump's published flow volume at that voltage. Most electric fuel pump manufacturers have this information.

Remember that the fuel pump must be wired correctly to achieve optimal perfor-mance. This means using heavy-gauge wire (typically 10-gauge), a relay, and a good ground. Yes, higher voltage at the pump terminals increases motor torque, resulting in increased fuel-pump flow volume. In testing, an electric fuel pump at 80 psi produced a 40-percent increase in volume when voltage increased from 12 to 13.5 volts. Wire a high-dollar electric pump incorrectly, and the pump's performance will suffer due to insufficient voltage.

There are two elements critical to an electric fuel pump's ability to support flywheel horsepower. The first is the pressure at which the fuel pump is required to deliver fuel volume. Second is the horsepower consumed by the engine accessories ahead of the flywheel. Higher fuel pressures created by boost-reference fuel systems, typically found on forced-induction EFI engines, load and slow down electric fuel pumps, which reduces available fuel pump volume.

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