1. What is Fuel Injector Size Calculation?

The fuel injector size calculation determines the required flow rate (in lb/hr) for fuel injectors based on engine horsepower, fuel consumption, number of injectors, and their duty cycle. Proper sizing ensures adequate fuel delivery for optimal engine performance.

2. How Does the Calculator Work?

The calculator uses the injector sizing equation:

Where:

• \( HP \) — Engine horsepower
• \( BSFC \) — Brake specific fuel consumption (typically 0.4-0.6 lb/HP-hr for gasoline)
• \( n_{injectors} \) — Number of fuel injectors
• \( duty\_cycle \) — Maximum injector duty cycle (typically 0.8 or 80%)

Explanation: The equation calculates the required fuel flow per injector while accounting for the number of injectors and their maximum operating duty cycle.

3. Importance of Proper Injector Sizing

Details: Correct injector sizing is critical for engine performance. Undersized injectors can cause lean conditions and engine damage, while oversized injectors can cause poor idle quality and drivability issues.

4. Using the Calculator

Tips: Enter engine horsepower, BSFC (use 0.5 for most gasoline engines), number of injectors, and desired maximum duty cycle (typically 0.8 for safety margin).

5. Frequently Asked Questions (FAQ)

Q1: What is a typical BSFC value?
A: For gasoline engines: 0.45-0.55 lb/HP-hr (naturally aspirated), 0.55-0.65 (forced induction). Diesel engines typically have lower BSFC.

Q2: What duty cycle should I use?
A: 80% (0.8) is common to allow headroom for variations and safety margin. Never exceed 90% in calculations.

Q3: How does boost affect injector sizing?
A: Forced induction increases BSFC. Use higher BSFC values (0.55-0.65) for turbocharged/supercharged engines.

Q4: Should I round up my injector size?
A: Yes, it's recommended to round up to the nearest available injector size for safety margin.

Q5: How do I convert lb/hr to cc/min?
A: Multiply lb/hr by 10.5 to get cc/min (for gasoline with specific gravity ~0.72-0.77).