Katerina Swanson
The amount of hose required for a return fuel system depends on several factors, including the make and model of the car, the type of fuel pump, and the size of the engine. The hose is the vital link that joins all the components of the fuel system together, and it is important to choose the right type and size of hose to ensure the system functions properly and safely. The most common sizes of hose for fuel systems are 6mm (1/4), 7.3mm, 8mm (5/16), and 10mm (3/8), and the size of the hose will determine the required fittings. The type of hose and fittings used will also depend on the pressure of the fuel system, with low and high-pressure options available.
| Characteristics | Values |
|---|---|
| Hose type | R9 specification fuel hose, Teflon/PTFE-lined hose |
| Hose size | 6mm (1/4"), 7.3mm, 8mm (5/16"), 10mm (3/8") |
| Fittings | Red, blue, or black |
| Hose bore and thread size | Dash 6 (-6) or dash 8 (-8) |
| Return line size | -6 AN (3/8") -8 AN (1/2"), -10 AN (5/8") |
| Feed and return line sizes | -10 feed and -8 return, -12 feed and -6 return, -10 feed and -10 return |
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Fuel hose sizing
For older, smaller-engined cars with carburettors, a 6mm hose size is typically suitable. Larger-engined cars, on the other hand, may require a 10mm hose. Fuel-injected cars often use larger hose sizes, ranging from 12mm to 15mm from the tank to the pump, depending on the specific application. It's important to note that these hose sizes refer to the internal diameter, which is the standard measurement for fuel hose sizing.
When it comes to return fuel lines, it is common practice to use a size smaller than the feed line. For high-performance engines, a common setup is to use a -10 AN (5/8") hose for the fuel supply and a -06 AN (3/8") hose for the return line. However, it's worth noting that some sources recommend using a -8 AN (1/2") hose for the return line to avoid any potential restrictions that could increase fuel pressure.
The type of fuel also plays a role in fuel hose sizing. When designing a fuel system for Ethanol or Methanol, it is recommended to go one or two sizes larger than the gasoline requirement. For example, R9 specification fuel hose, which is designed to withstand Ethanol, is available in sizes ranging from 6mm (1/4") to 10mm (3/8"). This type of hose is often used with fittings that mechanically clamp to the hose, providing a secure connection.
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Hose durability
Fuel hoses are essential components of a vehicle's fuel system, delivering fuel from the tank to the engine. While they are often inconspicuous, their proper functioning is vital for the vehicle's performance and safety.
Fuel hoses are not immune to wear and tear and can fail over time, leading to reduced performance and potential safety hazards. The durability of a fuel hose depends on various factors, including the quality of the hose, compatibility with the fuel type, exposure to temperature extremes, and proper installation.
Low-quality hoses or mismatched clamps can lead to premature failure. It is important to select a hose that is compatible with the type of fuel it will carry to prevent degradation. For example, hoses that are not resistant to Ethanol can perish, swell, crack, and ultimately fail under its influence. R9 specification fuel hoses are designed to withstand Ethanol and provide better value in the long term due to their durability and reduced risk of fuel leaks and fires.
Exposure to high heat or freezing temperatures can also weaken hose materials over time. Hoses made of different materials have varying durability; for instance, metal fuel lines are more durable than rubber hoses and can withstand the harsh conditions of the engine better. Teflon-lined braided stainless steel hoses are highly durable and flexible, offering excellent fuel permeability, reduced wear, and increased safety. They are resistant to abrasion and corrosion, ensuring longevity.
Additionally, proper installation is crucial to hose durability. Incorrect hose length, twisting during installation, or improper clamping can lead to kinking, restricted fuel flow, and structural damage. Regular inspections and maintenance can help identify repair issues before they become more significant problems.
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Hose fittings
When selecting hose fittings, it is important to consider the compatibility with the hose and the fuel system. Some common types of hose fittings include:
- JIC/AN fittings: These are typically used on competition cars and high-performance vehicles. They are sized based on a combination of thread size and hose size.
- Quick-release fittings: These are found on some modern cars and allow for easy connection and disconnection of the hose.
- Screw-on fittings: These are commonly used on competition cars and high-performance vehicles. They provide a secure connection but require identifying the correct type of fitting and thread.
- Compression fittings: These fittings use a compression olive to create a strong connection with the hose. They are typically used with Teflon/PTFE-lined hoses, which are suitable for both inside and outside the car due to their ability to prevent the escape of fuel vapour.
It is important to choose the correct size and type of hose fittings to ensure a secure and leak-free connection. Additionally, the hose and fittings should be inspected regularly for any signs of degradation, especially in fuel injection return lines, which are common sources of fuel leaks. Replacing the hose and fittings if they show any wear or damage is essential to maintaining a safe and reliable fuel system.
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Fuel system plumbing
Firstly, determine the type of fitting required. Most production cars use push-on hoses, with an 8mm bore being the most common. If your vehicle has a replacement tank that has removed the in-tank pump, it may have a built-in regulator, which is common in single-point injection cars. In such cases, you may need to add a regulator in the return line to allow the fuel system to pressurise.
When selecting a hose, consider the fuel type and pressure requirements. The R9 specification fuel hose is designed for pump fuel with ethanol content and provides better value in the long run due to its durability and reduced risk of fuel leaks and fires. The hose comes in various sizes, such as 6mm, 7.3mm, 8mm, and 10mm, and can be used for carburettor and injection applications. The fittings mechanically clamp to the hose, ensuring a secure connection.
For high-performance engines, consider using Teflon/PTFE-lined hoses, which can be used inside and outside the car. These hoses prevent the escape of fuel vapour, eliminating the stale fuel smell. They are available in dash 6 (-6) or dash 8 (-8) sizes and come with stainless steel over-braid. The fittings, available in colours like red, blue, or black, clamp securely to the hose with a compression olive.
Additionally, pay attention to the threads used in the fuel system. Common thread types include Metric, JIC/AN, NPTF, and BSP. AN fittings, developed by the aerospace industry, are sized based on the outside diameter of metal tubing, with each size indicating a 1/16-inch increase. For example, a -3 fitting represents 3/16 inch, -4 represents 1/4 inch, and so on.
Finally, consider the placement of the fuel pump and the routing of the hoses. If using an electric fuel pump, it is often mounted under the car directly in front of the fuel tank. When making sharp turns, use angled fittings like 45-degree or 90-degree elbows instead of bending the hose. A 3-inch radius is the maximum bend for a rubber hose.
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Fuel regulator
Return-style regulators are a
Non-return style regulators, on the other hand, are typically found in older vehicles with carburettors. They lack a fuel return line, which reduces weight, complexity, and expense. Fuel enters through an inlet port, passes through a fuel control valve, and is distributed through an outlet port to the carburettor. While this type of regulator may not be suitable for high-fuel flow and pressure applications, it is suitable for low-pressure systems found in vintage cars.
When selecting a fuel regulator, it is important to consider the specific requirements of your engine and fuel system. Factors such as hose size, bend radius, and pressure settings need to be taken into account to ensure optimal performance and safety.
In terms of hose size, fuel regulators typically use different hose sizes for the supply and return lines. For high-performance engines, a common combination is a -10 AN (5/8") supply line and a -6 AN (3/8") return line. However, it is always important to refer to the manufacturer's instructions, as some regulators specify a minimum return line size, such as -8 AN (1/2"). Additionally, the bend radius of the hose should be considered, with large return lines requiring limited bends to function properly.
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Frequently asked questions
A return fuel system is a one-way fuel system that is used in cars with fuel injectors.
The type of hose used for a return fuel system depends on the type of car and fuel system. Common hoses include R9 specification fuel hose, which is resistant to ethanol, and Teflon-coated braided steel hose, which can be used inside and outside the car.
The size of the hose may depend on the make and model of the car. For example, a Camaro with a 496 ci engine uses an 8 AN fuel supply and a 6 AN return line. It is recommended to use a hose that is one size smaller for the return line than the feed line.
In addition to the size and type of hose, it is important to consider the length of the hose and the number of fittings required. The hose should be long enough to reach all the necessary components with some bend, and the number of fittings will depend on the design of the fuel system.
To ensure the correct hose has been chosen, it is recommended to flush the plumbing pieces with solvent and air to remove any debris before making the final connections. If the car does not run properly, clamping the return pipe or adding a regulator to the return line may be necessary.
