Variable compression nozzles were part of Andorian battle cruisers in the 2150s. This advanced equipment allowed the cruiser to easily keep the anti-matter stream into the engines at an acceptable limit. This prevented user error due to negligence or loss of ability to control the pressure inside the warp reactor.
In 2153, Thy'lek Shran was asked for the schematics for the variable compression nozzles by Commander Charles Tucker III, stating that the nozzles "would do wonders for our engines." Shran was initially apprehensive, calling the nozzles "a sensitive piece of information," but eventually agreed. (ENT: "Proving Ground")