Accelerate an engine can be replaced with a number of synonyms that serve the same purpose. Some of the commonly used synonyms include rev up the engine, give the engine some gas, step on the pedal, press the accelerator, put the foot down, and speed up. All these phrases imply the same action of increasing the engine's speed and power output. These synonyms may be used in different situations and contexts, but they all convey the same intention of pushing the engine to deliver more power. It is essential to note that some of these phrases may be colloquial or informal, and it is crucial to use them appropriately.