Green’s Dictionary of Slang

1. (US) of a car engine, customized.

1954		R. Fabian London After Dark 83: One [car] was registered in his name [...] the other was provincially registered and hidden. This was the ‘hotted-up’ job.
1956		‘Charles Raven’ Und. Nights 12: He heard a door slam and soon after the engine note of a hotted-up sports car.
1979		Lette & Carey Puberty Blues 54: She came over to say goodbye, glancing in the back of his hotted-up panel van.
1988		A. Payne ‘The Last Video Show’ in Minder [TV script] 32: He drives around in this hotted up car that does about a mile to the gallon.
1993		Smith & Noble Neddy (1998) 108: As soon as I left home, I realised that I was being followed. Several hotted-up cars kept right behind me.
2019		C. Hammer Silver [ebook] Jasper and his hotted-up Mazda [...] Fanging along Dunes Road, shattering the speed limit.

2. excited.

2011

J.J. Connolly Viva La Madness 252: Giles is getting hotted-up ... he loosens his tie, undoes his top button.