A method for controlling a powertrain of a vehicle, the powertrain comprising: an engine comprising mutually independently operable valves, the engine being configured to be operated in a four-stroke operation mode, and a drivetrain comprising a transmission,
the method comprising: while operating the engine in the four-stroke operation mode, identifying that a critical situation applies or is expected to apply, in which a fast downshift of the transmission is required, initiating a downshift process in response to the identification of the critical situation, during at least a part of the downshift process, increasing an engine speed by controlling at least the mutually independently operable valves of the engine such that the engine is temporarily operated in a two-stroke operation mode.

A two stroke internal combustion engine having a piston reciprocating in a cylinder between TDC and BDC positions to influence a crank shaft with help of a connecting rod. A Rotational Valve (RV) associated with the cylinder body selectively altering the timing and duration of opening and closing of cylinder intake and exhaust ports. The said rotational Valve may be associated with the said crank shaft through a drive train assembly. Drive train assembly may control the Rotational Valve through electronic or mechanical means.

Described herein is a system for variable actuation of an engine valve of an internal-combustion engine, where the system is able to actuate the engine valves, selectively, in a four-stroke operating mode and in a two-stroke operating mode, on the basis of the operating conditions of the engine.

Described herein is a system for variable actuation of an engine valve of an internal-combustion engine, where the system is able to actuate the engine valves, selectively, in a four-stroke operating mode and in a two-stroke operating mode, on the basis of the operating conditions of the engine.

An exhaust valve includes a toroidal surface about an axis of rotation of the valve. The toroidal surface is positionable over a central exhaust port of an engine when lowered. The valve is raised by an actuator in response to increasing rotational speed of the crankshaft of the engine, thereby enlarging and raising the effective opening of the exhaust port. Lateral valve surfaces on either side of the toroidal surface close lateral exhaust ports when the valve is lowered. The lateral valve surfaces may be cylindrical and formed on fins. The position of the exhaust valve is adjusted continuously along its range of motion and the position of the exhaust valve may be calculated based on some or all of engine speed, engine loading, and exhaust temperature at a frequency up to once per revolution of the engine.