Engine arrangement

A method for operating an engine arrangement with a first internal combustion engine and a second internal combustion engine in a vehicle, the method comprising:

• partially coupling a first crankshaft of the first internal combustion engine in the vehicle with a second crankshaft of the second internal combustion engine in the vehicle to start the second internal combustion engine, where the first crankshaft and second crankshaft are partially coupled with a clutch;
• decoupling the first crankshaft and the second crankshaft when the second engine is operating under its own power;
• and
• coupling the first crankshaft and the second crankshaft, where the first and second crankshafts are coupled with the clutch when a speed difference between the first and second crankshafts is below a predetermined value and a relative angular position between the first and second crankshafts is less than 360°.

A method for controlling an engine arrangement including a first and a second internal combustion engine, each engine including a crankshaft and at least one cylinder with a piston connected to said crankshaft, a controllable friction clutch arranged between the crankshafts, an engine control unit connected to and configured to control the first and second engine, and sensors for monitoring at least one operating parameter for the engines, the method being carried out when the first engine is operated, the method comprising the steps of:

• detecting a demand for output torque exceeding an available output torque from the first engine;
• starting the second engine and increasing its engine speed towards the engine speed of the first engine;
• comparing a first engine speed of the first engine and a second engine speed of the second engine;
• controlling the second engine to minimize the difference between the first and the second engine speed;
• comparing a relative angular position of the crankshafts of the first and second engines and a relative angular position of the camshafts of the first and second engines;
• controlling the relative angular position of the crankshafts of the first and second engines using a sensed crankshaft position and the ignition timing sequence of the respective first and second engines;
• and
• controlling the controllable friction clutch to lock up the crankshafts of the first and second engines in at least one predetermined relative angular position.