Sylvie Willis
Selecting the right size fuel pump for 400cc injectors is critical for performance and tuning control. Fuel pumps are sized by flow rate, which is the amount of fuel a pump can supply over time, usually measured in gallons per hour (GPH) or litres per hour (LPH). The flow rate can be affected by various factors such as voltage, amp draw, and pressure. Additionally, factors such as fitment, which refers to the injector inlet and outlet size and the length of the injector, also play a role in determining the appropriate fuel pump size. To calculate the required fuel pump size, one can use formulas that consider factors like projected horsepower, Brake Specific Fuel Consumption (BSFC), and injector size.
| Characteristics | Values |
|---|---|
| Fuel pump size | Sized by flow rate, usually measured in gallons per hour (gph) or liters per hour (lph) |
| Flow rate | Amount of fuel a pump can supply over time; can be calculated by multiplying peak horsepower by BSFC (Brake Specific Fuel Consumption) |
| Fuel Injector size | Critical for performance and tuning control; can be calculated using FuelTech's Fuel Injector Calculator |
| Fuel Injector flow rate | Usually advertised statically at 43.5 PSI |
| Fuel Injector Calculator | Requires number of fuel injectors, estimated horsepower, and type of induction as inputs |
| Fuel Injector Control | Can be achieved using a Peak & Hold driver box added to any ECU |
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What You'll Learn
Fuel injector flow rates are usually 43.5 PSI
Fuel injector flow rates are usually advertised at 43.5 PSI. This is the standard base fuel pressure, and it is important to understand how this affects the performance of your engine.
Firstly, it is worth noting that the fuel flow rate is the amount of fuel a pump can supply over time, usually measured in gallons or litres per hour. This is an important factor in determining the size of the fuel pump you require. The fuel flow rate is directly impacted by the fuel pressure. As pressure increases, the flow rate decreases, and vice versa. This is a critical inverse relationship to understand when selecting a fuel pump.
At 43.5 PSI, the fuel injectors will be working at a lower pressure, which is easier on the fuel pump. This means that your fuel pump will not need to work as hard to deliver the required fuel flow rate. However, it is important to ensure that your injectors can still support your horsepower requirements at this lower pressure.
To calculate the maximum horsepower capacity, you can use the following rough rule of thumb: injector # per hour x number of injectors x 2 = max hp capacity. For example, if you have 79# injectors, 79 x 8 x 2 = 1264 hp. This calculation provides an estimate of your engine's fueling capacity.
Additionally, when considering the flow rate, it is important to account for any desired duty cycle and drive line loss. This may require some downward adjustments to your calculations.
By understanding the standard base fuel pressure of 43.5 PSI and its impact on fuel flow rates, you can make informed decisions about the size and specifications of your fuel pump and injectors to ensure optimal engine performance.
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Flow rate is the amount of fuel a pump can supply over time
Fuel pumps are rated in either litres or gallons per hour. One US gallon is equivalent to 3.785 litres or 231 cubic inches, and one litre is equal to approximately 0.26 US gallons. The best way to find the flow rate at a given pressure is to check a fuel pump's curve chart. For example, a pump with a free-flow rate of 78 gph will have a flow rate of 62 gph at 60 psi.
The old rule of thumb says a "good" fuel pump will flow about half a gallon per minute, but some engines need more than this. The fuel delivery specifications need to be looked up to see if the pump is delivering an adequate supply of fuel to the engine. The volume of fuel flowing through the return line will drop as engine speed increases because more fuel is flowing through the injectors.
The flow rate of a pump is dependent on the amount of psi it is putting out. As pressure increases, the pump has to work harder and becomes less efficient, and the flow volume decreases. The same goes for the fuel filter, which is also located inside the fuel tank with the pump module. If fuel pressure is low, disconnect the vacuum hose to the regulator or check the sensors that control the regulator in the tank.
To determine the required fuel pump size for forced induction engines, take the projected horsepower and multiply it by 0.47 to determine litres per hour. Injectors are normally rated in cubic centimetres (cc) per minute. Take the calculated fuel pump size in litres and divide the number by 16.67.
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Fuel pump size is the amount of fuel flow, not the pump's physical size
When choosing a fuel pump, it's important to understand that the term "size" refers to the volume of fuel the pump can flow, not its physical dimensions. This is an important distinction because the amount of fuel a pump can supply over time, also known as the flow rate, is a critical factor in the performance and efficiency of your engine.
The flow rate of a fuel pump is usually measured in gallons per hour (GPH) or liters per hour (LPH). It represents how much fuel the pump can deliver at a specific pressure. For example, a pump with a free flow rate of 78 GPH at 60 psi may see a drop in flow rate to 62 GPH as the pressure increases. This relationship between pressure and flow rate is essential to consider when selecting a fuel pump.
To determine the right fuel pump for your engine, you need to consider both the fuel volume and fuel pressure demands of your vehicle. This means taking into account factors such as vehicle horsepower and brake-specific fuel consumption (BSFC). By using resources like fuel injector calculators and consulting experts in the field, you can make an informed decision about the appropriate fuel pump size for your specific application.
Additionally, it's worth noting that voltage plays a significant role in the performance of electric fuel pumps. Higher voltage at the pump terminals can increase motor torque, resulting in a higher flow volume for a given pressure. This is an important consideration, especially when dealing with high-performance engines or racing vehicles.
In summary, when referring to fuel pump size, it's essential to understand that the size indicates the amount of fuel flow the pump can deliver, not its physical dimensions. By considering factors such as flow rate, fuel volume, fuel pressure, vehicle horsepower, and voltage, you can select the right fuel pump to meet the demands of your engine, ensuring optimal performance and efficiency.
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Fuel flow volume is measured in gallons-per-hour (GPH)
Fuel flow volume is typically measured in gallons-per-hour (GPH) or litres-per-hour (LPH). This measurement is critical when selecting the right fuel pump for your horsepower delivery. It is also known as gal/hour, gallon/hour, gallon per hour, gallons per hour, gallon/hr, or gal/hr. This unit is commonly used in the US unit system.
The formula to calculate the optimal GPH is: (Max. HP x BSFC) / 6. BSFC, or brake-specific fuel consumption, is a measurement of the amount of fuel consumed per unit of power produced. An engine typically requires 0.5 pounds of fuel per horsepower every hour at wide-open throttle. This number generally applies to naturally aspirated engines.
For example, a 200 HP engine with a BSFC of 0.5 would consume 100 pounds of fuel per hour. Dividing this by 6 gives a GPH of 16.66, or 17 when rounded up.
The formula to calculate the optimal LPH is: (Max. HP x BSFC) / 1.585. A gallon of fuel weighs 6 lbs, so to get GPH, you divide lbs/hr by 6. A litre of fuel weighs about 1.6 lbs, so to get LPH, you divide lbs/hr by 1.6.
The best way to find the flow rate at a given pressure is to check a fuel pump’s curve chart. This will show how voltage affects flow rate, and how amp draw increases with pressure.
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Fuel injectors are rated in cubic centimetres (cc) per minute
The flow rate of a fuel injector is critical for performance and tuning control. It determines how much fuel can be delivered to the engine at a specific pressure. Most fuel injector flow rates are advertised statically at 43.5 PSI, which means that the fuel flow is measured while the injector is fully open, and fuel is pumped through at this pressure.
To maintain the advertised flow rate, the fuel pressure should be adjusted according to changes in the pressure in the intake manifold. For example, if the static fuel pressure is set to 43.5 PSI and the manifold pressure increases to 30 PSI, the fuel pressure should be raised to 73.5 PSI.
The proper fuel injector size is crucial for engine performance. High impedance injectors are more common for street applications, while low impedance injectors require a peak-and-hold injector driver, which allows for a higher opening current.
To determine the appropriate fuel injector size, one must consider factors such as the number of injectors, estimated horsepower, and the type of induction. Online calculators and conversion tools are available to assist in selecting the correct fuel injector size, ensuring optimal engine performance.
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Frequently asked questions
Fuel pumps are sized by flow rate, which is the amount of fuel a pump can supply over time. The flow rate is usually measured in gallons per hour (GPH) or liters per hour (LPH). The best way to find the flow rate at a given pressure is to check a fuel pump’s curve chart.
You need to select a fuel pump that will meet your engine’s fuel volume and fuel pressure demands. The average advertised weight of a gallon of premium fuel is 6.34 lb/gallon. Brake Specific Fuel Consumption or BSFC is the projected amount of fuel required to produce 1 HP for 1 hour.
Minimum flow rate needs can be calculated by multiplying peak horsepower by BSFC. This will give you fuel usage in lbs/hr. For example, a naturally aspirated 500-horsepower engine has a BSFC of about 0.5. It would use 250 lbs of fuel per hour.
The fitment is the injector inlet and outlet size and the length of the injector. Running a fuel pump that is larger than you need should not cause any problems. However, you do want to avoid the potential for fuel waste and excess work on the part of the fuel pump if you are using one that is too large.
