the method and the device serve to adapt the valve characteristic of a fuel injection valve , which has a piezoelectrically driven nozzle needle and by which fuel is injected directly into the combustion chamber of an internal combustion engine , to production - related or age - related variations in the injection behavior . the activation energy and the needle stroke of the fuel injection valve are controlled in such a way that the engine torque in the case of a fuel injection valve with a reference characteristic would not vary . here , if an actually occurring variation in the engine torque is detected , then by varying the gradient of the activation - energy / valve - stroke characteristic curve of the fuel injection valve , the engine torque is matched to the engine torque generated with an injection valve with a reference characteristic .