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BMEP

Brake Mean Effective Pressure
Engineering Term & Method of Comparing All Engines
BMEP-PSI = Average Cylinder Pressure in PSI

Two Stroke -- BMEP = HP x 6500 / L x RPM
Four Stroke -- BMEP = HP x 13000 / L x RPM


L = Displacement in Litres (80 cc = .08 Litres) (700 cc = .7 Litres)

Note: 3% Loss of HP & Air Density -- each 1000 ft. of Elevation Above Sea Level

Examples: 1000 T- Cat 166 hp @ 8400 rpm
(166 hp x 6500 = 1079000) / (1 x 8400) = 128.45 BMEP
(190 hp x 6500 = 1235000) / (1 x 8400) = 147.02 BMEP

Ported T Cat ~ Exhaust TA (time area) = 155.6 BMEP @ 8400 rpm
155.6 / (6500 / 8400) = 0.7738 ~ 155.6/.7738 = 201.08 hp

700 Yamaha Mtn. Max 140 hp @ 8200 rpm
(140 x 6500 = 910000) / (.7 x 8200 = 5740) = 158.53 BMEP
142 hp @ 8000 rpm (923000) / (5600) = 164.82 BMEP
150 hp @ 9000 rpm (975000 / (6300) = 154.76 BMEP

982 SRX Union Bay 211 hp @ 8900 rpm
(211 x 6500 = 1371500) / (.982 x 8900 = 8739.8) = 156.93 BMEP

Good way to compare engine volumetric efficiency. Engine compression in psi plus pipe working at 110% may? come close to BMEP. If your BMEP is not higher than your compression psi -- you have a problem.
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