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Fuel Injector Calculator

Calculate required fuel injector size for a target horsepower.

Introduction

Fuel Injector Calculator — Calculate required fuel injector size for a target horsepower. Enter Target horsepower, Number of injectors, BSFC, Max duty cycle to get an instant, accurate result.

Formula

Required injector size (lb/hr) = (target horsepower × BSFC) / (number of injectors × max duty cycle), where BSFC (brake-specific fuel consumption) is roughly 0.5 lb/hp/hr naturally aspirated and 0.6 turbocharged.

Step-by-step

  1. Enter the Target horsepower.
  2. Enter the Number of injectors.
  3. Enter the BSFC.
  4. Enter the Max duty cycle.
  5. Click Calculate to see your result instantly.

Real-world example

Example: With Target horsepower = 400, Number of injectors = 4, BSFC = 0.55, Max duty cycle = 0.8, the Fuel Injector Calculator gives a result of 68.75.

Frequently Asked Questions

Why cap max duty cycle below 100%?
Running injectors at their absolute maximum duty cycle (typically capped at 80% here) leaves no margin and can cause poor fuel atomization and injector wear — a safety buffer is standard practice.
Why is BSFC higher for turbocharged engines?
Forced induction typically runs richer air/fuel mixtures for safety and cooling under boost, which increases fuel consumption per horsepower produced.
What inputs does the Fuel Injector Calculator need?
You'll need to provide: Target horsepower, Number of injectors, BSFC, Max duty cycle. All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.
How accurate is the Fuel Injector Calculator?
The Fuel Injector Calculator applies the formula exactly as calculated — Required injector size (lb/hr) = (target horsepower × BSFC) / (number of injectors × max duty cycle), where BSFC (brake-specific fuel consumption) is roughly 0.5 lb/hp/hr naturally aspirated and 0.6 turbocharged. — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.
Is the Fuel Injector Calculator free to use?
Yes, the Fuel Injector Calculator is completely free, requires no signup, and runs instantly in your browser.

About the Fuel Injector Calculator

The Fuel Injector Calculator uses a real, verifiable formula — Required injector size (lb/hr) = (target horsepower × BSFC) / (number of injectors × max duty cycle), where BSFC (brake-specific fuel consumption) is roughly 0.5 lb/hp/hr naturally aspirated and 0.6 turbocharged. — so results are accurate every time, not an approximation.