Fuel Injector Flow & Efficiency Calculators

Key terms often used:

• IDC = Injector Duty Cycle. Typically 80% for safe margin.
• RPM = Engine Revolutions per Minute.
• IPW = Injector Pulse Width, Length of time injector is open for a pulse measured in milliseconds.​

“Injector duty cycle” describes the percentage of time a fuel injector is open and supplying fuel during one engine cycle. It shows how long the injector is “on” relative to the total time of the engine cycle, as a percentage. A higher duty cycle means the injector is open for a part of the cycle, resulting in more fuel delivery.

There are various methods to solve formulas, similar to most equations, depending on the positioning of the variables relative to the assignment operator and whether one is multiplying or dividing. One way to calculate the injector duty cycle, divide the injector pulse width (the duration the injector is open by the engine cycle time (the time for one complete engine cycle), then multiply the result by 100 to convert it into a percentage. The formula is: (Injector Pulse Width / Engine Cycle Time) x 100% = Injector Duty Cycle. Key terms often encountered include: – RPM = Engine revolutions per minute – IPW = Injector Pulse Width (the duration the injector is active).

Key terms often used:

• IDC = “Injector Duty Cycle”, is percentage of time a fuel injector is open and supplying fuel during one engine cycle. Typically 80% for safe margin expressed as a decimal .8 in this case.
• lb/hr = “Pound Per Hour”, unit of mass flow that is derived from the international avoirdupois pound.
• cc/min = “Cubic Centimeters Per Minute”, unit used to quantify the flow rate of a fluid.
• BSFC = “Brake-Specific Fuel Consumption”, how much fuel your engine will use per hour for each horsepower it makes.

This Injector Size Calculator is designed to assist in identifying the appropriate size of injector for your specific application.

The injector flow rate refers to the quantity of fuel that a fuel injector dispenses over a specific time period, typically measured in pounds per hour (lbs/hr) or cubic centimeters per minute (cc/min). This measurement is crucial for the fuel injection system, as it helps establish the appropriate fuel-to-air ratio for an engine.

There are various methods to solve formulas, similar to most equations, depending on the positioning of the variables relative to the assignment operator and whether one is multiplying or dividing. One way to calculate the flow rate of a fuel injector, one can apply the following formula: (Engine Horsepower x Brake Specific Fuel Consumption (BSFC)) / Number of Injectors. This calculation yields the necessary fuel flow rate for each injector. The BSFC is a metric that indicates the amount of fuel consumed by an engine for each horsepower generated, generally falling within the range of 0.45 to 0.65, contingent upon the type of engine, such as naturally aspirated or turbocharged.

Fuel Injector Max Capacity Calculator

​Key terms often used:​

• IDC = “Injector Duty Cycle”, is percentage of time a fuel injector is open and supplying fuel during one engine cycle. Typically 80% for safe margin.
• lb/hr = “Pound Per Hour”, unit of mass flow that is derived from the international avoirdupois pound.
• cc/min = “Cubic Centimeters Per Minute”, unit used to quantify the flow rate of a fluid.
• BSFC = “Brake-Specific Fuel Consumption”, how much fuel your engine will use per hour for each horsepower it makes.
• IFR = “injector flow rate”, the amount of fuel an injector can deliver over a period of time. It’s measured in pounds per hour lbs\Hr or cubic centimeters per minute cc\min
• BSFC : Normally Aspirated Engines = .45 – .5 ,   Nitrous Oxide Engine = .6 – .65 ,    Forced Induction Engines = .6 – .75

​Key terms often used:

RPM = Engine Revolutions per Minute.

BSFC = Brake-Specific Fuel Consumption, how much fuel your engine will use per hour for each horsepower it makes.

IFR = “injector flow rate”, the amount of fuel an injector can deliver over a period of time. It’s measured in pounds per hour lbs\Hr or cubic centimeters per minute cc\min

​​General Gasoline BSFC values to use when making calculations

• Normally Aspirated Engines = .45 – .5
• Nitrous Oxide Engine = .6 – .65
• Forced Induction Engines = .6 – .75

Calculator to convert ‘lb/hr ‘to ‘cc/min’ and vice versa.