Engine Friction Loss Calculator

Estimate engine friction losses (FMEP) across speed range using the Chen-Flynn friction model per SAE standards.

Input Parameters

Results

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FMEP
bar
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Friction HP Loss
hp
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Mechanical Efficiency
%
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Dominant Source
Note: The Chen-Flynn model is widely used in SAE literature for friction estimation. Piston/ring friction is 40-50% of total, bearings 20-30%, valve train 10-15%, and accessories 10-20%.

Reference

FMEP = C0 + C1×P_max + C2×MPS + C3×MPS² Chen-Flynn: C0=0.4, C1=0.005, C2=0.09, C3=0.0009 Mean Piston Speed = 2 × Stroke × RPM / 60 Friction Power = FMEP × Disp × RPM / (2 × 60) Mech Efficiency = BMEP / (BMEP + FMEP)