Injector Size Calculator — Find the Right Fuel Injectors

Injector Size Calculator

Calculate the optimal fuel injector size for your engine based on horsepower, fuel type, and target air/fuel ratio. Ensure proper fueling for performance builds.

Step 1: Engine Details

Understanding Fuel Injector Sizing

Proper injector sizing is critical for engine performance and reliability. Too small injectors will limit power, while too large injectors can cause poor idle and driveability issues.

Step 2: Fuel System Details

12.5
80%

About Duty Cycle

Duty cycle represents the percentage of time an injector is open during an engine cycle. For reliability, aim for 80-85% maximum duty cycle to allow headroom for variations in fuel demand.

Fuel Injector Sizing Results

Summary
Injector Comparison
Flow Rate Analysis

Recommended Injector Size

42.5 lb/hr
≈ 445 cc/min
Fuel Flow per Cylinder
42.5 lb/hr
Total Fuel Flow
255 lb/hr
BSFC Estimate
0.55 lb/hp-hr
Injector Category
Performance

Common Injector Sizes

Injector Size lb/hr cc/min Typical HP Support Application

Injector Flow Rate Analysis

Injector Sizing Formula

Injector Size = (HP × BSFC) / (Cylinders × Duty Cycle)

Fuel injector sizing is calculated based on the engine’s horsepower, brake specific fuel consumption (BSFC), number of cylinders, and the desired injector duty cycle. Actual requirements may vary based on fuel type, forced induction, and specific engine characteristics.

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