Tech Answer

Please explain proper fuel delivery.

Fuel Delivery
Many racers experience fuel delivery problems without ever being aware that something is amiss in their fuel systems. State-of-the-art engines produce a lot more power than a race engine of ten years ago. The process of producing horsepower revolves around the conversion of fuel into energy. The more pounds of fuel an engine can burn efficiently per hour, the more horsepower it produces. Even though your car may not miss, pop, bang, skip or do anything else peculiar, it may not be getting all the fuel it needs to make maximum power.

In oval track applications, a BG Belt Drive Fuel Pump is preferred where use of a mechanical fuel pump is specified. This pump offers the highest fuel delivery volume of any mechanical pump yet maintains low fuel pressure at low engine speeds. This alleviates "loading up" of the spark plugs. The BG Six-valve and Super Speedway mechanical fuel pumps will also deliver ample fuel volume when used according to recommendations.

For drag race cars, a BG400-2 Electric Fuel Pump is the best way to guard against fuel starvation. If a drag car is "lazy" at mid-track or "lays down" then pulls well in higher gear, the engine may be experiencing intermittent fuel starvation. Typically, the carburetor bowls are full at the starting line so the car leaves hard but subsequently drains the bowls dry. In lower gears, the car accelerates rapidly with the engine picking up rpm very quickly. When the float bowl fuel level drops, the car "lays down" because of fuel starvation. In high gear, engine speed increases more slowly allowing the bowls to fill again.

To assure adequate fuel delivery, the fuel system should be capable of filling a one-gallon metal gas container at the carburetor fuel inlet in 25 seconds or less. Do not use a Super Jug or antifreeze jug - they are not accurate. Large displacement, high horsepower engines should have a fuel system that can pump a gallon in less than 20 seconds. Remember, to get fuel into the engine, the jets have to be covered. Whenever a race car slows for no apparent reason, fuel delivery is the first thing to check. This holds true for both single and dual four-barrel installations. In fact, single four-barrel applications frequently have more severe fuel starvation problems than dual four-barrel installations. This is because a single four-barrel has only two fuel bowls and two inlet needle and seat assemblies. With dual four-barrels, there are four needle and seat assemblies and four fuel bowls. This doubles the fuel handling capability.

For the same reason, only filters specifically designed for racing, such as the BG5000 or BG Inline filter, should be installed. Use of a filter is strongly advised as long as it doesn’t restrict fuel flow. The fuel filter should be inline before the fuel pump. This filters the fuel, preventing any damaging material from entering the fuel pump or the rest of the system.

Fuel pressure should be set between 6 and 8 psi for a gasoline carburetor where an alcohol carburetor requires 4 to 5 psi at idle and 9 to 12 psi at wide open throttle. Fuel pressure is not a substitute for volume and if the fuel bowls aren’t full, pressure is meaningless. In fact, fuel pressure is simply an indication of the amount of restriction in the fuel system.

Most electrical fuel pump systems require the use of a fuel pressure regulator. One BG regulator is sufficient in many applications. The use of 2 regulators is recommended when using other types of regulators or in high horsepower engines to avoid excessive fuel restriction and provide adequate volume.

With mechanical fuel pumps, and some electrical pumps, a bypass is preferred rather than a regulator. A diaphragm bypass without an idle bleed is recommended when constant fuel pressure is needed from an electrical or mechanical pump. A belt driven fuel pump, using gasoline or alcohol, requires a diaphragm bypass with an idle bleed. Higher pressure mechanical fuel pumps delivering alcohol, such as our 15 psi BG Six-valve, require a throttle bypass to supply the variable fuel pressure required by the carburetor.

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