The nozzles on the jet engines open up as the engines increase in power, this is incorrect. when the engines are off or at idle they should be completely open, as the engines increase in power, the nozzles should close to constrict the exhaust gasses in order to increase exhaust flow velocity.

See the following video as well as other videos on this channel for information on jet engine operation.
https://youtu.be/x5ccK94IvsA