Mean Effective Pressure - PME vs BMEP
Relationship between indicated (PMI) and brake (BMEP) mean effective pressure with mechanical efficiency - cross-checks indicator card against brake power test.
BMEP
19.53bar
FMEP
1.47bar
Formula, assumptions, and limits
$$\text{BMEP} = \eta_{mech} \cdot \text{PMI}, \quad \text{FMEP} = \text{PMI} - \text{BMEP}$$
Slow-speed mech. eff. 92–95 % at MCR; medium-speed 85–90 %. Declining η over time indicates bearing wear or timing-gear drag.
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $PMI$ | Indicated mean effective pressure | bar | indicator card |
| $BMEP$ | Brake mean effective pressure | bar | shaft torque meter |
| $FMEP$ | Friction mean effective pressure | bar | PMI − BMEP |
| $\eta_{mech}$ | Mechanical efficiency | - | brake test |
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