Abstract: The present invention relates to an arrangement for an internal combustion engine. The engine is of the kind which has a number of working cylinders (1, 2, 3, 4), each of which communicating with a corresponding auxiliary cylinder (5, 6, 7, 8). Each working cylinder has a working piston (9, 10, 11, 12) which is so arranged as to execute a reciprocating motion and, via a connecting rod (9a, 10a, 11a, 12a), the working piston is operatively connected to a first crankshaft (17). Each auxiliary cylinder (5-8) has an auxiliary piston (13, 14, 15, 16) which is so arranged as to execute a reciprocating motion and via a connecting rod (9a-12a), the auxiliary piston is operatively connected to a second crankshaft (18). Acting between the aforementioned crankshafts is a device (19, 20, 21) to ensure that the motion of the auxiliary piston (13-16) occurs in a relation to the motion of the working piston (9-12), and to provide angular displacement between the shafts (20, 21).

Abstract: For improving the efficiency of an Otto cycle engine operating under varying loads, an opposing piston is provided above the driving piston in each cylinder and is controlled in accordance with the inlet manifold depression so as to vary the compression ratio and maintain the compression substantially constant with different working loads.