Last updated on .From the section Formula 1

Force India were fourth in last year's constructors' championship

Force India and Toro Rosso became the final two teams to unveil their 2018 cars before the start of pre-season testing on Monday.

Both teams showed off their cars in the pit lane at Spain's Circuit de Barcelona-Catalunya about an hour before running started at 0800 GMT.

Force India's appears an evolution of last year's car, which finished fourth in the constructors' championship.

Toro Rosso are embarking on their first season with new engine partner Honda.

The Japanese manufacturer split from factory partner McLaren last year, just three years into an arrangement that was expected to last nearly a decade, after regularly poor performance and reliability.

Red Bull has taken on Honda with its junior team to give it options with the senior team in the future.

This is effectively a year when Red Bull will decide whether to switch from Renault engines for 2019, following years of coolness in their relationship as a result of the French company's inability to match standard-setters Mercedes' one engine performance.

New Zealander Brendon Hartley will drive the Toro Rosso on the first day of this week's four-day test.

At Force India, development driver Nikita Mazepin will run on Monday. Race drivers Esteban Ocon and Sergio Perez will drive over the rest of the week.

Force India have set themselves the target of maintaining their fourth-place finish this season, despite what is expected to be a greater threat from McLaren and the factory Renault team.

The team also revealed that there was a "greater than 50% probability" that they will change their name before the start of the season in Australia next month.

Chief operating officer Otmar Sazfanauer said: "We haven't quite decided (the name) and it also needs to go through the formal approval progress. There is a probability it will change before the first race."