CORRELATION AND PRESENTATION OF DIESEL-ENGINE PERFORMANCE DATA 510184
THE author shows that when engines of a particular group are assumed to be exactly similar, whatever their size, the following parameters are appropriate for comparing the performance, when measures of quality independent of cylinder size are desired:
Mep, both brake and indicated.
Mean piston speed.
Power per unit piston area.
Weight per unit piston displacement.
He develops a graph of bmep versus piston speed, with lines of constant specific fuel consumption and lines of constant power output per square inch of piston area, which gives a complete story of engine performance, and can be compared with similar plots for other engines, regardless of cylinder size or number of cylinders.