Injector Size Calculator UK

Injector Size Formula:

\[ \text{Injector Size (lb/hr)} = \frac{HP \times BSFC}{\text{Number of Injectors} \times \text{Duty Cycle}} \]

HP (horsepower):

BSFC (lb/HP-hr):

lb/HP-hr

Number of Injectors:

Duty Cycle (decimal):

(0-1)

Injector Size:

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1. What is the Injector Size Calculation?

The Injector Size calculation determines the required fuel injector flow rate based on engine horsepower, brake-specific fuel consumption, number of injectors, and duty cycle. This ensures proper fuel delivery for optimal engine performance.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ \text{Injector Size (lb/hr)} = \frac{HP \times BSFC}{\text{Number of Injectors} \times \text{Duty Cycle}} \]

Where:

\( HP \) — Engine horsepower
\( BSFC \) — Brake-specific fuel consumption (lb/HP-hr)
\( \text{Number of Injectors} \) — Total number of fuel injectors
\( \text{Duty Cycle} \) — Injector duty cycle as a decimal (0-1)

Explanation: This formula calculates the minimum flow rate required per injector to adequately supply fuel to the engine at maximum power output.

3. Importance of Injector Sizing

Details: Proper injector sizing is crucial for engine performance, fuel efficiency, and preventing lean conditions that can cause engine damage. Undersized injectors can limit power, while oversized injectors can cause poor idle and drivability issues.

4. Using the Calculator

Tips: Enter engine horsepower, BSFC value (typically 0.45-0.65 for naturally aspirated engines, 0.55-0.75 for forced induction), number of injectors, and desired duty cycle (typically 0.8-0.9 for maximum performance).

5. Frequently Asked Questions (FAQ)

Q1: What is a typical BSFC value?
A: BSFC typically ranges from 0.45-0.65 lb/HP-hr for naturally aspirated engines and 0.55-0.75 lb/HP-hr for forced induction engines.

Q2: What duty cycle should I use?
A: For maximum performance, use 0.8-0.9 (80-90%) duty cycle to allow some headroom. For daily driving, 0.7-0.8 is common.

Q3: How do I convert lb/hr to cc/min?
A: Multiply lb/hr by 10.5 to get cc/min (approximately). Different fuels may have slightly different conversion factors.

Q4: Should I size injectors for peak power or normal driving?
A: Size for peak power requirements, but ensure injectors aren't so large that they can't properly control fuel flow at idle and low loads.

Q5: What happens if I exceed the recommended duty cycle?
A: Exceeding 90% duty cycle can cause injectors to overheat, lose accuracy, and potentially fail. It's recommended to stay below 85% for reliability.