BSFC Calculator

Brake specific fuel consumption (BSFC) measures the fuel efficiency of a shaft-power-producing engine. The fundamental formula evaluates the fuel consumption rate relative to the engine's power output: BSFC = (3600 * Fuel Consumption) / Power. Here, fuel consumption is typically measured in grams per second (g/s) or pounds per hour, while power is measured in kilowatts (kW) or horsepower (hp). The constant 3600 accounts for converting seconds to hours when calculating hourly fuel usage. Additionally, engine power can be derived from torque and rotational speed using the equation Power = (Torque * RPM) / 9.5488. Lower BSFC values denote higher efficiency, meaning the engine extracts more work from every drop of fuel.

Let us calculate the brake specific fuel consumption for a high-performance gasoline engine producing 250 kW of power while consuming fuel at a rate of 14.78 grams per second. First, apply the standard BSFC formula: multiply the fuel consumption rate by 3600 to find the hourly fuel consumption (14.78 g/s * 3600 s = 53,208 grams per hour, or 53.208 kg/h). Next, divide this hourly consumption by the power output: BSFC = 53.208 kg/h / 250 kW = 0.2128 kg/kW·h. This result indicates that the engine requires 212.8 grams of fuel to generate one kilowatt-hour of mechanical energy, representing a highly efficient operating point for modern internal combustion engines.

When measuring fuel consumption and power for BSFC calculations, always ensure your engine has reached normal operating temperatures to avoid cold-start discrepancies. Pay close attention to unit consistency: mixing metric units (grams, kilowatts) with imperial units (pounds, horsepower) will yield incorrect outputs unless converted properly. Finally, remember that BSFC varies across the RPM and throttle range; mapping multiple operating points helps you identify the engine's sweet spot for maximum fuel economy and endurance racing performance.