Rajan Wilcox
When it comes to fuel lines, there are a number of factors that determine the appropriate size, including the pressure, pump, and horsepower. For 700 hp, a 3/8 line is generally considered suitable, and can support well over 1000 hp. However, some sources suggest that for supercharged engines above 700 hp, it wouldn't hurt to step up to a 1/2 or #8AN line. It's important to consider the specific application and requirements, and in some cases, seeking advice from the manufacturer or a specialist may be beneficial.
| Characteristics | Values |
|---|---|
| Fuel line size for 700 hp | 3/8" line, #6 line, #8 line, #10 line, 1/2" line |
| Fuel line size for 600 hp | 3/8" line, #6 line, #8 line |
| Fuel line size for 900 hp | #8 line, #10 line |
| Fuel line size for 1000 hp | #10 line, 1/2" line |
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What You'll Learn
A 3/8 fuel line is suitable for most applications
For example, a 3/8" line is sufficient for a vehicle with 700 HP that is street-driven. However, if the vehicle is going to be raced and needs to be fed at 6500 RPM, a larger 1/2" line is recommended.
The suitability of a 3/8" fuel line also depends on the type of pump being used. A large mechanical pump may not perform well with a small line, but an electric pump that pushes the fuel might handle it better. Additionally, the fittings and bends in the line can impact performance.
Some applications that use a 3/8" fuel line include:
- Bearhawk aircraft with a Continental IO-360 engine
- Motorcycle fuel lines
- Auxiliary fuel tank addition to generators
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A 1/2 line is recommended for 700 hp engines that are supercharged
When it comes to high-performance engines, ensuring adequate fuel supply is crucial. For a 700 hp engine, the fuel line size becomes a critical factor in achieving optimal performance. While some might assume that a larger fuel line is always better, this isn't necessarily the case. It's important to find the right balance to meet the engine's fuel demands without compromising efficiency.
In the case of a 700 hp engine, a 1/2-inch fuel line is generally recommended, especially if it's supercharged. This recommendation is supported by both theoretical calculations and practical experiences shared by enthusiasts. A 1/2-inch line provides sufficient fuel flow to meet the demands of a 700 hp engine, ensuring that the engine receives the required amount of fuel for proper combustion.
To understand why a 1/2-inch fuel line is sufficient, let's delve into some calculations. At Wide Open Throttle (WOT), a typical Brake Specific Fuel Consumption (BSFC) of 1/2 pound of fuel per horsepower is considered safe. This results in A/F ratios of 11:1 or richer, with maximum HP occurring at an A/F ratio of 13:1. Given that gasoline weighs approximately 5.994 lbs per gallon, you would need 1 gallon of gasoline per 12 HP.
Now, let's consider the flow rate. A 700 hp engine requires approximately 350 lbs/hour of fuel, which equates to 60 gallons per hour. Using a flow rate calculator for a 3/8-inch tube at 60 GPH shows that it operates well below the critical velocity, indicating that a 3/8-inch line is indeed sufficient for 700 hp. However, when it comes to supercharged engines, the demands on the fuel delivery system increase significantly.
Superchargers introduce additional complexity by requiring a substantial amount of fuel just to spin the supercharger itself. This means that the fuel delivery system must supply enough fuel to both power the supercharger and feed the engine's power requirements. In such cases, stepping up to a 1/2-inch fuel line can provide the necessary capacity to meet the increased fuel demands of a supercharged 700 hp engine.
Additionally, practical experiences shared by enthusiasts reinforce the recommendation of a 1/2-inch fuel line for 700 hp supercharged engines. Several individuals have reported successful outcomes with this setup, achieving impressive performance without experiencing fuel delivery issues. Therefore, for a supercharged 700 hp engine, a 1/2-inch fuel line is the recommended choice to ensure sufficient fuel flow and optimal performance.
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A 3/8 steel line could support 1000 HP with a big enough pump
A 3/8" steel line can support 600 HP with sufficient "pump head". This is because the key to sufficient fuel supply is pumping power. A bigger pump, higher pump voltage, and/or increasing the line size can increase pump head. A 3/8" steel line can support 1000 HP with a big enough pump.
To determine whether a bigger pump is needed, an electronic fuel pressure gauge can be installed. If the pressure falls as the engine RPM increases, more pump head is required.
It is important to note that fuel pump measurements are typically made in volume versus mass, although mass is more accurate. To calculate the amount of fuel needed to support 1000 HP, we can use a BSFC (Brake Specific Fuel Consumption) of 0.5 pounds of fuel per horsepower, resulting in A/F ratios of 11:1 or richer. This means that 1 gallon of gasoline can support 12 HP, and therefore 1000 HP would require 83.3 gallons of gasoline per hour.
When considering the pressure drop through a 3/8" steel line, we can calculate the head loss per 100 feet of pipe. Using the Cameron Hydraulic Data handbook, we find that the head loss for a new steel pipe of 0.364" id at 1.388 gpm (83.3 gph) is 35 feet per 100 feet of pipe with water as the medium. Converting this to psi, we get 15 psi per 100 feet. For a 20-foot steel pipe, this would result in a pressure drop of 3 psi using water, while gasoline would be slightly less viscous and flow more freely.
Increasing the line size to 1/2" would result in a much smaller pressure drop, with a nominal 5 feet versus 35 feet for the 3/8" id fuel line. This would result in a 1/2 pound drop versus a 3-pound drop for the 3/8" line at the stated flow of 83.3 gph, which is enough to support 1000 HP at a BSFC of 0.5. Therefore, a 3/8" steel line can support 1000 HP with a big enough pump.
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A #8 line is efficient enough for 900 hp motors
When it comes to high-horsepower applications, one common question is whether a fuel line needs to be increased in size to support higher horsepower. For instance, whether a #6 fuel line needs to be upgraded to a #8 or #10 to support 600 HP. However, this is not always necessary, as a 3/8" id fuel line can support 600 HP with sufficient "pump head". In fact, given a large enough pump, a 3/8" steel line could even support 1000 HP.
Now, regarding the specific statement, "A #8 line is efficient enough for 900 hp motors", this does appear to be true according to sources. One source mentions that a friend who works at a company that dynoes motors stated that a #8 fuel line is efficient enough for 900 hp motors. Additionally, in a discussion about fuel line size for 700 hp, one user mentions using a #8 supply/return with no fuel delivery issues. Another user with 650 hp mentions using a #8 from the regulator to the carb.
It's worth noting that some users with higher horsepower engines opt for larger fuel lines. For example, one user with an 800 HP engine mentions installing a -10an fuel line (equivalent to 5/8") for both the feed and return. Similarly, another user with a 700 hp BBC engine uses a #10 line from the pump to the regulator and a #8 return line.
Ultimately, the decision on fuel line size may depend on various factors, including the specific engine configuration, the type of fuel, and the desired safety margin. However, based on the available information, it appears that a #8 fuel line can indeed be efficient enough for 900 hp motors.
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A #6 line is plenty big for EFI
When it comes to fuel line sizing, a common misconception is that a larger line is needed to support higher horsepower. For instance, it is often asked whether a 3/8" ID fuel line needs to be increased to at least 1/2" ID to support 600 HP. However, this is not the case, as a 3/8" ID fuel line can easily support 600 HP with sufficient "pump head".
Now, let's delve into why a #6 line is indeed plenty big for EFI (Electronic Fuel Injection). Firstly, it's important to understand that EFI systems can handle higher back pressure without issues. While a return line with high back pressure can cause problems in a carbureted engine, EFI engines can typically tolerate 30 PSI of back pressure without any concerns. This means that a #6 line has more than enough capacity to handle the fuel flow requirements of an EFI system.
Additionally, it's worth noting that EFI engines often have equal-sized feed and return lines. While a carbureted engine may require different sizes for the feed and return lines, EFI systems usually utilise the same size for both. This further supports the argument that a #6 line is sufficient for EFI applications.
Furthermore, when it comes to fuel pumps, a #6 line can accommodate the flow requirements of a single 525 HP engine without issues. Beyond that, the flow velocity increases, and additional pressure is needed at the pump to achieve the desired flow at the engine. However, for engines producing up to 700 HP, a #6 line is still adequate, as evidenced by real-world examples provided by experienced enthusiasts.
In conclusion, a #6 line is indeed plenty big for EFI applications, even at higher horsepower levels. As long as sufficient pump head is provided, a #6 line can support EFI engines with excellent performance and efficiency.
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Frequently asked questions
A 3/8" line is suitable for most applications. However, if you are supercharged and over 700 hp, you could consider stepping up to a 1/2" or #8AN line.
A larger fuel line will provide more volume and ensure the engine does not get starved of fuel.
A 3/8" line is sufficient for 600 hp.
A 10 line is recommended for 1000 hp on EFI.
A 9 line is efficient enough for 900 hp.
