Spain's double world champion Fernando Alonso and Brazilian Nelson Piquet joined team boss Flavio Briatore in presenting Renault's R29 car to photographers on a damp and cloudy morning.
The drivers and team officials were due to talk to the media at the end of the day.
Renault, eager to cut costs amid the global financial crisis, had scrapped a planned launch at the Le Castellet circuit in southern France in favour of a simple presentation at a regular test.
Williams also gave their car a low-key debut, rolling the Toyota-powered FW31 out of the garage for a brief photo-call before German test driver Nico Hulkenberg took it out on track for the first installation laps.
The British-based team are hoping major rule changes this season will allow them to climb back up the standings after a disappointing 2008 saw them slip to eighth overall.
McLaren, who will have world champion Lewis Hamilton at the wheel on Wednesday, and Toyota were also testing their new cars at the Portuguese circuit after launches last week.
Switzerland's Sebastien Buemi, the 20-year-old who will be the youngest driver on the starting grid this season, was testing for Toro Rosso after being confirmed by the Ferrari-powered team earlier this month.
Image: Renault Formula One drivers Fernando Alonso and Nelson Piquet unveil the new R39 car with Managing Director of the Renault F1 team Flavio Briatore, at Algarve racetrack
Photograph: Jose Manuel Ribeiro/Reuters