You can watch a heart-stopping car race, filled with excitement.
In the sentence, is the phrase "filled with excitement" an adverb phrase or adjective phrase?
If it is an adjective phrase, does it need a comma in front? Thanks a lot.
Yes, it's an adjective phrase functioning as a 'predicative adjunct': 'predicative' because it relates to a predicand (the subject "you"), and 'adjunct' because it's an optional element. Compare:
(1) "You are filled with excitement". [Predicative complement]
(2) "You can watch a heart-stopping race, filled with excitement". [Predicative adjunct]
In both those examples, the property of being filled with excitement applies to the subject "you", hence 'predicative'. But in (1) the AdjP is a complement, an obligatory element, whereas in (2) it's an adjunct, not of the modifying kind, but a loosely attached element set off with a comma, sometimes called a 'supplement'.