Engine Friction Mean Effective Pressure Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 26, 2026Engine Friction Mean Effective Pressure Calculator
The gap between what an engine produces internally (indicated work) and what actually reaches the flywheel (brake work) is friction, pumping losses, and accessory drive - all captured in one number: FMEP.
Formula: FMEP = IMEP - BMEP
Example: an IMEP of 1,200 kPa and BMEP of 950 kPa gives an FMEP of 250 kPa, corresponding to a mechanical efficiency of 79.2%.
How to Use This Calculator
- Enter indicated mean effective pressure (from in-cylinder pressure measurement).
- Enter brake mean effective pressure (from dynamometer torque measurement).
Production engines commonly show FMEP in the range of roughly 100-400 kPa depending on design, speed, and load - a useful diagnostic figure for identifying how much internal friction is costing usable output.