A Bulls man has appeared in court this morning to face a manslaughter charge after the violent death of a teenager in downtown Auckland.

Eli Francis Holtz, 18, was assaulted at the intersection of Wellesley St West and Queen St early on Saturday morning.

He died in hospital on Sunday evening.

Holtz was a passenger in a car that stopped at the intersection's traffic lights at 3.15am, police said yesterday.

The 30-year-old man accused of manslaughter after the assault appeared briefly this morning in the Auckland District Court.

Judge Nicola Mathers remanded him without plea to reappear in the High Court at Auckland next month.

She also granted him interim name suppression to protect his fair trial rights.

The alleged offender was initially charged with wounding with intent to cause grievous bodily harm before the charge was upgraded to manslaughter this morning.

Police withdrew the grievous bodily harm charge.

Holtz was from Whangarei and plans were being made to return the teen's body to Northland. It is understood he had previously attended Bay of Islands College in Kawakawa.

An autopsy on Holtz's body was done yesterday and detectives were reviewing CCTV footage, Detective Inspector Scott Beard said.

Police also want to speak to the occupants of a white Toyota Prius that was behind the victim's vehicle at the time of the assault.