1. What is the Injector HP Calculation?

The Injector HP calculation estimates the maximum horsepower supported by a fuel injection system based on injector flow rate, number of injectors, duty cycle, and engine efficiency (BSFC). This helps in selecting properly sized injectors for an engine.

2. How Does the Calculator Work?

The calculator uses the injector HP formula:

Where:

• \( injector\_lbhr \) — Flow rate of one injector in pounds per hour
• \( n\_injectors \) — Number of injectors
• \( duty\_cycle \) — Maximum safe duty cycle (typically 0.80-0.85)
• \( BSFC \) — Brake Specific Fuel Consumption (lb/HP-hr)

Explanation: The equation calculates the total fuel flow available from all injectors at a given duty cycle, then divides by the engine's fuel consumption rate to determine supported horsepower.

3. Importance of Injector Sizing

Details: Proper injector sizing is crucial for engine performance. Undersized injectors can limit power potential, while oversized injectors can cause poor idle quality and drivability issues.

4. Using the Calculator

Tips: Enter injector flow rate in lb/hr, number of injectors, duty cycle (typically 0.80 for safety margin), and BSFC (0.45-0.50 for NA engines, 0.55-0.60 for forced induction).

5. Frequently Asked Questions (FAQ)

Q1: What is a typical BSFC value?
A: Naturally aspirated engines: 0.45-0.50, Turbocharged engines: 0.55-0.60, Supercharged engines: 0.55-0.65 lb/HP-hr.

Q2: What duty cycle should I use?
A: 80% (0.80) is a safe maximum for continuous operation, though some applications may briefly use up to 90%.

Q3: How do I convert cc/min to lb/hr?
A: Multiply cc/min by 0.126 to get lb/hr (for gasoline with SG ~0.737).

Q4: Should I include all injectors?
A: Yes, include all primary injectors. Secondary injectors (if used) would be calculated separately.

Q5: What if my engine uses E85?
A: For E85, multiply the calculated HP by ~0.7 (or use ~30% higher BSFC) as it requires more fuel flow.