What is Brake-Specific Fuel Consumption (BSFC)?

Brake-Specific Fuel Consumption (BSFC) is a crucial metric in evaluating the efficiency of internal combustion engines. It measures the relationship between fuel consumption and delivered power, providing insights into an engine’s performance beyond mere fuel usage. While fuel consumption alone indicates how often you need to refuel, BSFC quantifies the engine’s output efficiency.

Calculating BSFC

To calculate BSFC, you need to know the engine’s output power (measured in watts) and fuel consumption (in grams per second). The formula is straightforward:


The power can be determined using the torque (τ) and rotational speed (ω) with the formula Power=τ×ω. A lower BSFC is desirable, indicating either reduced fuel consumption or increased power output.

Applications of BSFC Formula

1. Assessing Engine Efficiency

BSFC isn’t a direct measure of efficiency but can be used in conjunction with the energy density of the fuel. Multiply the BSFC by the energy density to gauge the fraction of input energy transformed into usable energy. Common energy densities include:

  • Methane: 0.0139 kWh/g
  • LPG: 0.01264 kWh/g
  • Gasoline: 0.01206 kWh/g
  • Diesel fuel: 0.01183 kWh/g
  • Kerosene: 0.01194 kWh/g

The efficiency (η) can then be calculated as:


2. Calculating Fuel Consumption

Engine fuel consumption varies across different operating regimes. Averaging BSFC over these regimes provides a reference value. To find fuel consumption (FuelConsumption), multiply BSFC by the power delivered by the engine:


Utilizing the BSFC Calculator

Our BSFC calculator simplifies these calculations. Choose your preferred measurement system and consider using additional converters for weight and energy. The tool allows reverse calculations, finding BSFC for desired efficiency or power corresponding to a fixed fuel consumption.

Make your automotive assessments more practical with our BSFC calculator. Explore other related tools for a holistic understanding, such as the fuel consumption calculator and the fuel cost calculator.

Frequently Asked Questions (FAQ)

What is BSFC?

BSFC, or Brake-Specific Fuel Consumption, measures an engine’s performance by indicating the amount of fuel required to deliver a specific power. Lower BSFC values suggest higher efficiency.

How to Calculate BSFC?

  1. Find the engine’s fuel consumption (r).
  2. Measure the power associated with that fuel consumption (P). You can also calculate power using P=τ×ω.
  3. Calculate BSFC as the ratio BSFC=Pr​.

Efficiency of a 250 kW Gasoline Engine with 14.78 g/s Consumption?

The efficiency is approximately 38.9%. Calculate BSFC, multiply it by gasoline’s energy density, and find the inverse to determine the engine efficiency.

Is a Lower BSFC Good?

Yes, a lower BSFC indicates higher power for the same fuel consumption or lower fuel consumption for the same power, signifying improved engine efficiency.