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Fuel Injector Size Formula:
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The Fuel Injector Size Formula calculates the required flow rate for fuel injectors based on engine horsepower, brake specific fuel consumption, number of injectors, and duty cycle. This ensures proper fuel delivery for optimal engine performance.
The calculator uses the formula:
Where:
Explanation: The formula calculates the fuel flow rate needed per injector to support the engine's power output while maintaining a safe duty cycle.
Details: Proper fuel injector sizing is crucial for engine performance, fuel efficiency, and preventing lean conditions that can damage the engine. Undersized injectors can't deliver enough fuel, while oversized injectors may cause poor idle quality.
Tips: Enter horsepower, BSFC (typically 0.45-0.65 for naturally aspirated engines, 0.55-0.75 for forced induction), number of injectors, and desired maximum duty cycle (usually 80-85% for safety margin).
Q1: What is a typical BSFC value?
A: For naturally aspirated engines: 0.45-0.55 lb/HP-hr. For turbocharged/supercharged engines: 0.55-0.65 lb/HP-hr. Racing engines may have higher values.
Q2: Why use 80% duty cycle?
A: A safety margin is recommended to account for variations in fuel pressure, voltage, and to allow headroom for power increases without replacing injectors.
Q3: Can I use this for diesel engines?
A: This formula is primarily for gasoline engines. Diesel injector sizing involves different calculations due to different fuel systems and combustion processes.
Q4: How does fuel pressure affect injector flow?
A: Injector flow rate changes with the square root of pressure ratio. Higher pressure increases flow, lower pressure decreases it.
Q5: What if I have different sized injectors?
A: This calculator assumes all injectors are the same size. For mixed sizes, calculate requirements for each bank separately.