3. The brake power (B.P.) of the engine is given by (where W = Brake load or dead load in newtons, l = Length of arm in metres, N = Speed of engine in r.p.m., S - Spring balance reading in newtons, D = Dia. of brake drum in metres, and d = Dia. of rope in metres)
7. During suction stroke of a four stroke petrol engine, the inlet valve opens and the charge is sucked into the cylinder as the piston moves upwards from the bottom dead centre.