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Free fuel injector calculator for sizing and flow rate calculations. Calculate injector size, duty cycle, BSFC, and flow rates for automotive performance tuning and engine modifications. Convert between cc/min and lb/hr with professional accuracy for turbo, supercharged, and naturally aspirated engines.
Last updated: February 2, 2026
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Engine horsepower at peak power
Typical: 0.45 (NA), 0.50-0.55 (Turbo), 0.60 (High boost)
Total number of fuel injectors
Base fuel pressure (standard is 43.5 PSI)
Recommended: 70-80% for safety margin
Required Injector Size
328.1 cc/min
(25 lb/hr per injector)
Total Flow Rate
200 lb/hr
Duty Cycle
80%
Status: Caution
Duty cycle is acceptable but high. Monitor fuel pressure and consider larger injectors for more headroom.
Injector Sizing Guidelines:
Output format
cc/min & lb/hr ratings
Determines proper injector size based on horsepower goals and BSFC
Safe range
70-80% optimal
Checks if existing injectors can safely support power output
Conversion factor
1 lb/hr = 10.5 cc/min
Easy conversion between imperial and metric flow measurements
BSFC range
0.50 - 0.60 typical
Accounts for higher fuel requirements of forced induction
Safety margin
10-20% headroom
Sizes injectors with extra capacity for future upgrades
Typical values
0.45 (NA) - 0.60 (Turbo)
Determines fuel efficiency for accurate injector sizing
For 400 HP engine with 0.50 BSFC and 8 injectors at 80% duty cycle:
Required Size
328.1 cc/min
Per Injector
25 lb/hr
Our fuel injector calculator uses industry-standard formulas to determine the proper injector size for your engine. The calculation accounts for target horsepower, BSFC (Brake Specific Fuel Consumption), number of injectors, and target duty cycle to provide accurate sizing recommendations for automotive performance applications.
Injector Size (cc/min) = (HP × BSFC ÷ # Injectors × 10.5) ÷ (Duty Cycle % ÷ 100)Where:
Injector flow rate vs duty cycle relationship
BSFC (Brake Specific Fuel Consumption) represents how much fuel an engine consumes per horsepower per hour. Lower values indicate better efficiency. Naturally aspirated engines typically run 0.45 lb/hp/hr, while turbocharged engines require 0.50-0.60 due to fuel enrichment for cooling and detonation prevention.
Need help with other automotive calculations? Check out our belt length calculator and sprocket calculator.
Get Custom Calculator for Your PlatformResult: Minimum 328.1 cc/min (25 lb/hr) per injector
Recommended: 350cc/min (33 lb/hr) injectors for 10% safety margin.
300 HP NA engine, BSFC 0.45, 6 injectors, 75% duty
Required: ~350cc/min (33 lb/hr) per injector
600 HP high boost, BSFC 0.60, 8 injectors, 80% duty
Required: ~590cc/min (56 lb/hr) per injector
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