Injector Size Calculator Hp

Injector Size Formula:

\[ Injector_{lb/hr} = \frac{HP \times BSFC}{n_{injectors} \times duty\_cycle} \]

Horsepower (HP):

Brake Specific Fuel Consumption (BSFC):

lb/HP-hr

Number of Injectors:

count

Duty Cycle:

fraction

Required Injector Size:

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1. What is the Injector Size Calculator?

The Injector Size Calculator determines the required fuel injector flow rate based on engine horsepower, fuel consumption, number of injectors, and duty cycle. Proper injector sizing is crucial for engine performance and reliability.

2. How Does the Calculator Work?

The calculator uses the injector size equation:

\[ Injector_{lb/hr} = \frac{HP \times BSFC}{n_{injectors} \times duty\_cycle} \]

Where:

\( HP \) — Engine horsepower
\( BSFC \) — Brake specific fuel consumption (lb/HP-hr)
\( n_{injectors} \) — Number of fuel injectors
\( duty\_cycle \) — Maximum injector duty cycle (decimal fraction)

Explanation: The equation calculates the required fuel flow rate per injector to support the engine's power output at the specified duty cycle.

3. Importance of Proper Injector Sizing

Details: Correct injector sizing ensures adequate fuel delivery without overworking the injectors. Undersized injectors can limit power, while oversized injectors may cause poor idle and low-speed drivability.

4. Using the Calculator

Tips:

For naturally aspirated engines, typical BSFC is 0.45-0.50 lb/HP-hr
For forced induction engines, typical BSFC is 0.55-0.65 lb/HP-hr
Recommended maximum duty cycle is 80-85% (0.80-0.85)
For safety margin, consider adding 10-15% to calculated size

5. Frequently Asked Questions (FAQ)

Q1: What is BSFC and how do I determine it?
A: BSFC (Brake Specific Fuel Consumption) is the fuel consumption rate per unit of power output. Use 0.5 for NA gasoline engines, 0.6 for turbocharged engines.

Q2: Why limit duty cycle to 80-85%?
A: Running injectors at 100% duty cycle can cause overheating and inconsistent fuel delivery. The 80-85% limit provides safety margin.

Q3: How does this change for E85 fuel?
A: For E85, multiply the calculated size by 1.3-1.4 as it requires more fuel volume for equivalent power.

Q4: What if I have staged injection?
A: For staged injection, calculate primary injectors for normal operation and secondary injectors for additional power.

Q5: How do I convert lb/hr to cc/min?
A: Multiply lb/hr by 10.5 to get cc/min (approximate conversion for gasoline).