Method for controlling a powertrain system during upshifting

A method for controlling a powertrain system of a vehicle during gear upshifting, said powertrain system comprising:

• an internal combustion engine system comprising an internal combustion engine configured to output a rotational speed via an engine output shaft;
• a transmission arrangement having a number of gear stages to obtain a set of gears, each one of the gears having a corresponding gear ratio, said transmission arrangement being operatively connected to the internal combustion engine via a transmission input shaft and further having a transmission output shaft for providing a rotational speed to one or more drive wheels of the vehicle,
• wherein said powertrain system further comprises a turbocharger arrangement having a turbine receiving exhaust gases from the internal combustion engine and a compressor for compressing intake air and feeding said intake air via an air intake line to said internal combustion engine, said turbine being configured to convert engine exhaust gas into mechanical energy to drive the compressor;
• the method comprising the steps of:
• operating the internal combustion engine in a four-stroke operation to provide engine rotational speed output via the engine output shaft;
• receiving an indication of an intended upshifting from a gear of the set of gears to a higher gear of the sets of gears;
• reducing the rotational speed of the engine output shaft by adjusting the operation of the internal combustion engine from the four-stroke operation to a two-stroke braking operation by controlling an inlet flow control valve assembly to open at least one inlet valve;
• when said internal combustion engine is in the two-stroke braking operation, performing the intended upshifting from said gear of the set of gears to said higher gear of the sets of gears and providing a flow of exhaust gases to the turbine during said step of performing the intended upshifting, thereby allowing the turbine to operate the compressor when said engine is in the two-stroke braking operation;
• and
• during each crankshaft revolution in the two-stroke braking operation, operating an exhaust flow control valve assembly to open in a first opening, when a piston moves from a bottom dead center, BDC, position to a top dead center, TDC, position, so as to receive fluid medium from an exhaust channel, and in a second opening, when the piston is just before the TDC position.