rev vs rev up

rev is a noun but rev up is not a noun.

Word	Noun	Adjective	Verb	Adverb
rev	Yes	No	Yes	No
rev up	No	No	Yes	No

As verbs, rev and rev up are synonyms defined as:

rev (noun)	rev up (noun)
rate of revolution of a motor

rev (verb)	rev up (verb)
increase the number of rotations per minute	increase the number of rotations per minute
	speed up