Engine BMEP (Brake Mean Effective Pressure)
Torque normalized by displacement, so engines of any size compare directly on how hard each cycle works: BMEP = 150.8 x torque(lb-ft) / displacement(CID) for a 4-stroke (75.4 for a 2-stroke). A 350 CID V8 at 400 lb-ft runs 172 psi -- squarely in the healthy naturally-aspirated gasoline range. NA gas engines top out near 180-190 psi because they fill on one atmosphere, so a BMEP above that is the signature of boost, and a low value points to a mild cam, a restriction, or wear. Evaluated at the torque peak from a corrected dyno pull. A comparison metric, not a design limit; the dyno sheet governs.
Formula and source
BMEP(psi) = 150.8 x torque(lb-ft) / displacement(CID) for a 4-stroke (75.4 for a 2-stroke); from BMEP = 2*pi*n_rev*T/V_d with T in lb-in and V_d in in^3.
Brake mean effective pressure (SAE; Heywood, Internal Combustion Engine Fundamentals), by name; the engine and its dyno sheet govern.
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