Fuel Pressure Secrets For Circle Track Motor Success

Fuel pressure is a critical factor in the performance and longevity of an engine, and circle track motors are no exception. The fuel pressure must be carefully calibrated to supply the correct air-fuel mixture for the engine's demands. Too little fuel pressure can cause the air-fuel mixture to go lean, leading to engine damage, while too much pressure can result in a rich mixture that causes the engine to miss and foul the spark plugs. Therefore, determining the correct fuel pressure is essential for optimal engine performance and to prevent costly failures.

Fuel pressure regulators: the price and quality of internal components need to be considered

Fuel pressure regulators are an important component of any EFI system, maintaining a steady fuel supply and ensuring the correct air-fuel mixture. The price of a fuel pressure regulator can vary from around $20 to over $300, depending on factors such as brand, features, and build quality.

The internal components of a fuel pressure regulator play a crucial role in its performance and durability. The quality of these components directly impacts the regulator's accuracy and longevity. For example, cheap springs and rubber diaphragms may not control fuel pressure as effectively as higher-quality alternatives.

When selecting a fuel pressure regulator, it is essential to consider the type of fuel used in the vehicle. Regular pump gas and race gases have different characteristics than alcohol-based fuels, which can be more harsh on the regulator's internal components. Manufacturers have developed harder coatings on components that come into contact with alcohol-based fuels to improve durability.

The size of the fuel pressure regulator is also a factor to consider. A larger regulator can handle more flow and higher pressure, which is often necessary for high-performance applications. Additionally, the regulator must be compatible with the specific fuel system and engine requirements.

In summary, when choosing a fuel pressure regulator, it is important to consider not only the price but also the quality of the internal components. Investing in a high-quality regulator with durable and precise internal components can improve engine performance and fuel efficiency while preventing engine damage.

Fuel pumps: the two most common methods of supplying fuel to a carburetor are with a remote electric fuel pump or a mechanical fuel pump

The fuel pump must be able to supply the proper fuel pressure and volume to the carburetor to ensure the correct air-fuel mixture for the engine's demands. For a race vehicle with a carbureted engine, the fuel pressure should be maintained at 5.5 to 6.5 pounds under all load conditions. If the fuel pressure is lower, the fuel level in the carburetor's float bowl will be too low, causing the air-fuel mixture to be too lean, which can lead to engine damage. On the other hand, if the fuel pressure increases, the float, needle, and seat will not be able to control the float level accurately.

The two most common methods of supplying fuel to a carburetor are with a remote electric fuel pump or a mechanical fuel pump mounted on the engine. Each type of pump has its advantages and considerations:

Remote Electric Fuel Pump

A remote electric fuel pump offers flexibility in mounting location, as it can be placed away from the heat of the engine near the fuel tank. This is beneficial if there are space constraints or excessive heat in the engine compartment. Electric pumps are also suitable for engines that were originally fuel-injected and lack the necessary mounting bosses for a mechanical pump.

When using an electric fuel pump, it is crucial to ensure proper fuel pressure control. A high-volume or race-electric fuel pump requires a bypass/return fuel pressure control system to keep the fuel flowing through the pump, preventing it from overheating and failing. Electric pumps are generally noisier than mechanical pumps, and their performance is highly dependent on proper installation practices.

Mechanical Fuel Pump

Mechanical fuel pumps are quiet in operation and do not require additional plumbing or wiring, making them a straightforward option. They are actuated by a lever that rides on a fuel pump cam lobe, creating suction to pull fuel from the tank and deliver it to the carburetor. Mechanical pumps have a preset fuel pressure that works well with typical two and four-barrel carburetors, and they do not require a fuel return line to the tank.

However, one drawback of mechanical pumps is that they may not provide sufficient pressure and volume for fuel injection conversions. Additionally, since they only pump fuel when the engine is cranking, it can take longer to start a vehicle that has been sitting for an extended period, as the fuel may have evaporated from the carburetor bowls and fuel lines.

Both remote electric and mechanical fuel pumps have their advantages and considerations. The choice between the two depends on factors such as engine specifications, space and heat constraints, and the type of fuel delivery system (carburetor or fuel injection). It is essential to match the fuel pump's capabilities with the specific requirements of the engine to ensure optimal performance and avoid issues such as insufficient fuel pressure or volume.

Fuel volume: the fuel pump must be able to supply the correct air/fuel mixture for the engine's demands

The fuel volume and pressure are critical factors in delivering the optimal air/fuel mixture to the engine. The fuel pump must be able to supply the correct fuel pressure and volume to the carburetor to achieve the desired horsepower. The fuel pressure for a race vehicle with a carbureted engine should be maintained between 5.5 and 6.5 pounds under all load conditions. If the fuel pressure deviates from this range, it can lead to adverse effects on the air/fuel mixture.

When the fuel pressure drops below the recommended range, the fuel level in the carburetor's float bowl decreases, resulting in a lean air/fuel mixture. This can cause engine damage and a loss of power. On the other hand, if the fuel pressure exceeds the upper limit, the float, needle, and seat become unable to control the float level accurately. Consequently, the air/fuel mixture becomes too rich, leading to engine misfires and spark plug fouling.

To ensure optimal performance, it is crucial to maintain the correct fuel pressure and volume. The fuel pump plays a vital role in achieving this by delivering the required amount of fuel to the carburetor while maintaining the appropriate pressure. The fuel pump's capacity and efficiency are key factors in this process.

The fuel pump's ability to deliver sufficient fuel volume is essential to maintaining the desired fuel pressure. The fuel volume required is influenced by factors such as engine load and horsepower. For instance, a typical engine demands 0.5 pounds of fuel per horsepower per hour. Therefore, an engine generating 300 horsepower will need approximately 25 gallons of fuel per hour at 6 pounds of fuel pressure.

Additionally, the fuel pump's performance is not solely dependent on its flow rate under zero pressure. When the pump maintains the necessary fuel pressure, the actual flow rate will be lower. This highlights the importance of selecting a fuel pump that can deliver adequate fuel volume while sustaining the required fuel pressure.

The type of fuel pump, whether mechanical or electric, also comes into play. Mechanical pumps are commonly mounted near the front of the engine, exposing them to high temperatures. On the other hand, electric pumps are often placed away from the engine, near the fuel tank, to mitigate heat-related issues. However, electric pumps must be equipped with a bypass or return fuel pressure control system to ensure continuous fuel flow and prevent overheating.

In summary, achieving the correct air/fuel mixture for the engine's demands relies on maintaining the appropriate fuel volume and pressure. The fuel pump plays a critical role in this process by supplying the necessary fuel volume while regulating fuel pressure. By considering factors such as engine load, horsepower, and the characteristics of the fuel pump, one can ensure optimal fuel delivery for peak engine performance.

Fuel lines: the minimum recommendation for fuel lines is 3/8 inch

The fuel lines are a critical component of a race car's fuel system. The minimum recommended size for fuel lines is 3/8 inch. This is important to ensure the engine receives enough fuel and does not starve for fuel.

Using proper fuel line size and low-restriction fittings is crucial for effective fuel system design. While steel tubing fuel lines are commonly used and work well, other options include aluminium tubing or steel-braided fuel lines. Rubber fuel hoses should only be used where their flexibility is specifically needed. It is also important to avoid 90-degree fittings, as these restrict fuel flow.

When designing a fuel system, it is imperative to follow the fuel pump supplier's recommendations for fuel line size, fuel tank supply, and venting lines. Additionally, the routing of the fuel lines should be carefully planned. Every effort should be made to keep the fuel line clear of hot exhaust components, while also maintaining a straight and direct path, free of sharp turns that could impede the flow of fuel.

Furthermore, the use of high-performance fuel hoses is recommended for routing fuel from the cell to the engine. These hoses are available in several variations, including braided stainless steel, socketless, and nylon-sheathed. Braided stainless steel hoses offer superior resistance to abrasion, while socketless or nylon-sheathed hoses are chosen for their lightweight properties.

In summary, ensuring that the fuel lines are of the recommended minimum size, properly routed, and constructed from suitable materials is vital for maintaining optimal fuel flow and pressure in a race car's engine.

Fuel filters: a dirty or neglected filter can restrict the fuel flow, causing the engine to run lean

Fuel filters are an important component of a race car's fuel system, but they are often neglected. Fuel filters ensure that debris from the fuel tank does not make its way into the carburetor or fuel injectors, which can cause engine damage. However, if a fuel filter is dirty or neglected, it can restrict fuel flow, causing the engine to run lean.

A lean-running engine is not getting enough fuel, which can lead to serious engine damage if left unchecked. The engine has to work harder to perform, and this added strain can eventually lead to irreparable damage. A lean-running engine will exhibit symptoms such as low power output, poor performance, and trouble starting.

The fuel filter is responsible for removing contaminants and dirt from the fuel. Over time, grime and debris build up in the filter, leading to a clog. If fuel cannot pass through the filter, it will not reach the engine, causing the engine to run lean. Therefore, it is important to change the fuel filter regularly as part of routine maintenance.

The specific fuel pressure requirements depend on the type of engine and fuel system. For a race vehicle equipped with a carbureted engine, the fuel pressure should be maintained between 5.5 and 6.5 pounds under all load conditions. If the fuel pressure drops below 4 pounds, the air/fuel mixture will shift lean, especially during wide-open throttle/high-load conditions.

To prevent a lean-running engine, it is crucial to ensure that the fuel filter is clean and functioning properly. Regular maintenance, including fuel filter replacement, is essential to avoid engine damage caused by a restricted fuel flow.

Frequently asked questions