Sylvie Willis
Building an effective fuel system for a race car is a complex task that requires careful consideration of various components and variables. The fuel system plays a critical role in delivering fuel from the tank to the engine, where it is mixed with air and ignited to generate torque. The system must be designed to handle different running conditions, from idle to wide-open throttle, and ensure optimal performance. When building a race car fuel system, it is essential to select high-quality products, including pumps, lines, filters, regulators, and injectors or carburetors. The fuel pump, in particular, needs to be appropriately sized to prevent over-fuelling and potential performance issues. Additionally, the hoses used should be routed with straight hose ends and different angle bends to ensure efficiency and longevity. Safety measures, such as rollover tubes and dry-break frangible couplings, are also crucial to prevent fuel leaks and reduce the risk of fires in the event of accidents. Building a race car fuel system requires a deep understanding of the engine's requirements and the ability to make informed choices to achieve optimal performance.
Characteristics and Values of a Race Car Fuel System
| Characteristics | Values |
|---|---|
| Fuel Tank/Cell | Must be large enough to hold fuel for the whole race; can be almost any size; made of military-grade ballistics material to prevent leaks |
| Fuel Pump | Must be appropriately sized for horsepower level and specific application; electric pumps are more common, but some race cars use mechanical pumps |
| Fuel Filter | Must be compatible with the type of fuel; cellulose filters are common for EFI systems; larger 'race' filters are available for big-power engines |
| Fuel Lines | Must be correctly sized and use appropriate fittings; use of different angle hose ends is recommended to ensure straight lines |
| Fuel Injectors | Must be able to deliver fuel at the correct pressure; multiple injectors per cylinder may be used to increase fuel flow and lower inlet temperatures |
| Fuel Pressure Regulator | Prevents over-fuelling of the engine |
| Fuel Type | Must consider the fuel type and any restrictions on the type of fuel pump required |
| Fuel Temperature | A concern due to heating from the engine and other components; in-tank pumps are recommended as they run cooler |
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What You'll Learn
Choosing the right fuel pump
When selecting a fuel pump, several factors must be considered. Firstly, the engine size and horsepower level play a vital role in determining the required fuel flow rate. As a general rule, a naturally aspirated engine requires approximately one gallon of gasoline per hour to support ten horsepower. This calculation varies depending on the fuel type, with E85 demanding 30% more volume, and methanol requiring twice the flow rate.
Additionally, the fuel delivery experts suggest using a 100- to 200-micron filter before the fuel pump to protect it from contaminants. As fuel flow increases, the surface area of the filter element must also increase to avoid restricting the fuel flow. It is also crucial to ensure that the filter element is compatible with the type of fuel being used.
Another critical decision is choosing between an in-tank or external fuel pump. In-tank fuel pumps, especially in EFI applications, are recommended as they run cooler, resulting in extended pump life and reduced noise. Furthermore, the class of racing and the associated restrictions on fuel pump type (electric or mechanical) should be considered. Mechanical pumps are generally externally mounted, while modern electric pumps offer flexibility in placement.
Finally, it is important to remember that an oversized fuel pump will not over-fuel the engine due to the fuel pressure regulator, but it can lead to frequent recirculation of fuel, causing a loss of performance and an increased risk of detonation due to fuel heating up. Therefore, it is always better to opt for a correctly sized fuel pump from the beginning.
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Selecting the right fuel filter
Type of Fuel
The type of fuel used in the race car is an important factor in selecting a fuel filter. Different fuels have different compatibility requirements with filter materials. For example, paper filters, also known as cellulose filters, are commonly used as disposable options, but they are not suitable for methanol or fuels with more than 20% ethanol content. In such cases, stainless steel filters are a better choice as they are compatible with all types of fuels and can be reused after cleaning. Micro Glass filters, on the other hand, are designed for post-pump use and are also disposable.
Micron Rating
The micron rating of a fuel filter refers to the size of the particles it can capture. The appropriate micron rating depends on the location of the filter in the fuel system. Before the fuel pump, a 100 to 200-micron filter is recommended to protect the pump, while after the pump, a finer filter with a rating of 5 to 40 microns is used to protect injectors or carburetors. For direct injection systems, a 5-micron filter is ideal, while a 10-micron filter is suitable for port injection, and a 40-micron filter for carbureted engines.
Surface Area
As fuel flow increases, the surface area of the filter element becomes crucial. Increasing the surface area ensures that the filter can handle the higher fuel volume without restricting flow. It's important to note that changing the micron rating of the filter is not the solution to managing higher fuel flow; instead, a larger filter with the same micron rating should be used to prevent damaging the filter and restricting fuel delivery.
Quality and Reliability
When it comes to fuel systems, it's essential not to compromise on quality. Opting for high-quality, American-made products from reputable companies like Aeromotive and Waterman can ensure optimal performance and longevity. While these products may carry a higher price tag, they can provide more dependable and efficient results, reducing the need for frequent replacements and maintenance.
By considering these factors and consulting with fuel delivery experts, racers can make informed decisions about selecting the right fuel filter for their race car fuel system, ensuring optimal performance, reliability, and protection for their engine.
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Hose and fitting selection
When selecting hoses and fittings for a race car fuel system, it is crucial to prioritize safety, performance, and compatibility. Here are some detailed guidelines to consider:
First and foremost, ensure that the hoses you choose are specifically designed for automotive fuel applications. These hoses should be made of materials that can withstand extreme temperatures, pressures, and corrosive fuels. Look for hoses with MIL SPEC hard anodizing, such as those with Ano-Tuff hard anodizing, as this treatment extends the life of the hose and fittings by adding an extra layer of structural integrity. This is especially important if you anticipate regularly removing and working on the hoses and fittings.
When routing the hoses, follow the advice of Cochran, who suggests, "When you are running your lines, you need to let the hose end route the hose, not just use straight hose ends and bend the hose. This is the reason we offer so many different degree bends. Hose is for taking fluid from point A to point B without getting it on the ground. The safest, most efficient way is a straight line, so use the different angles of the hose ends to accomplish this." Additionally, consider the environment in which the hoses will be used. For example, if the race car runs on corrosive fuels like alcohol, opt for hoses with Brite-Dipped ends to prolong their lifespan.
As for fittings, it is essential to select those that are compatible with your chosen hoses and fuel system components. Precision fittings are crucial to tying the fuel system together securely. Trusted brands like MagnaFuel and Earl's Fittings offer a range of fittings to choose from. When in doubt, consult experts or the technical departments of reputable fuel system companies for advice on the most compatible and suitable fittings for your specific application.
Lastly, remember that the weight of the hoses and fittings can impact the overall performance of the race car. If weight reduction is a priority, consider lightweight options like the Pro-Lite 350 hose and Ano-Tuff Auto-Crimp fittings. While these options may carry a higher upfront cost, they can provide long-term benefits in terms of performance and dependability.
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Fuel tank or cell
The fuel tank or cell is a pivotal component of a race car's fuel system, impacting the vehicle's performance and race tactics. There are two main options to consider: the fuel cell and the OEM fuel tank.
Fuel cells are specifically designed and built for racing, offering several advantages over traditional fuel tanks. They are made from robust materials like steel, aluminum, or high-strength plastic, providing superior impact resistance. Fuel cells feature safety bladders and anti-slosh foam to prevent fuel leakage and agitation, ensuring consistent fuel dispersal. They also have higher burst strength and are equipped with a non-vented cap and tip-over valve to prevent spilling during rollovers. The capacity of the fuel cell should be chosen based on the specific racing needs, considering race distance, vehicle type, and race frequency. For instance, a 10-gallon fuel cell is suitable for brief, high-intensity races, while a 20-gallon fuel cell is ideal for protracted or endurance racing events.
On the other hand, an Original Equipment Manufacturer (OEM) fuel tank offers convenience and cost savings. If the existing OEM fuel tank is in good condition, clean, and compatible with your fuel type, it can be reused with minimal modifications. However, older fuel tanks may pose challenges. They can clog pumps and injectors with contaminants and may not be rated for use with modern fuels, especially those containing ethanol. Therefore, it is crucial to consider the compatibility and longevity of the OEM fuel tank before reusing it.
When choosing between a fuel cell and an OEM fuel tank, it is essential to prioritize safety, performance, and compliance with racing regulations. Fuel cells are often required for sanctioned competitions due to their enhanced safety features. Additionally, specialized fuel tanks are custom-built for specific vehicles or racing applications, providing optimal fit, enhanced performance, and high safety standards.
It is worth noting that the fuel system's effectiveness also depends on other components, such as fuel pumps, filters, lines, and regulators. Ensuring proper sizing, maintenance, and compatibility with the fuel type is vital for optimal performance.
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Injectors or carburetor
Injectors or carburettors are an important consideration when building a race car fuel system. Carburettors are mechanical pumps that mix air and fuel, and their simplicity means there are no electronics to fail. However, fuel injection systems (EFI) are now widely used in racing, offering more power, efficiency, and precision.
EFI systems allow for a precise amount of fuel to be injected, suiting the airflow through the engine, and they are self-tuning. This precision also helps to regulate horsepower, making racing safer, and more fuel-efficient. The ability to download information from the electronic units of the cars will also play a role in the elimination of tandem drafting.
The use of EFI systems has been a recent development in racing, with NASCAR only switching to fuel injection in 2012. This change was made to bring racing technology more in line with the advancements of mass-produced vehicles. The transition was also seen as a way to stimulate technology companies to develop new innovations.
When building a race car fuel system, it is important to consider the type of fuel being used, as this will impact the filter element. For example, when using methanol, stainless steel filters and elements are recommended to ensure compatibility. It is also important to note that using overly large injectors can negatively impact idle quality and throttle response.
Overall, while carburettors have their advantages, fuel injection systems offer more advanced features and capabilities, making them the preferred choice for many race car fuel systems.
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Frequently asked questions
The key components of a race car fuel system are the fuel tank or cell, pump, filter(s), lines, rails (when applicable), regulator, and injectors or carburetor.
The fuel pump should be chosen based on the horsepower level and specific application. It should be able to deliver sufficient flow and pressure to the engine.
It is recommended to use a 100- to 200-micron filter before the fuel pump and a 5- to 40-micron filter before injectors or carburetors. The filter element should also be compatible with the type of fuel used.
The fuel regulator ensures that the fuel is delivered to the injectors at the correct pressure, allowing for accurate metering of the fuel quantity.
To prevent fuel leaks, it is essential to use high-quality hoses with dry-break frangible couplings. In the event of an accident or rollover, a flexible bladder made of military-grade ballistics material can contain the fuel and prevent leaks.
