McLaren has successfully fired up the Mercedes engine in its 2021 Formula 1 car for the first time.

Having agreed a deal to switch from Renault to revive its former engine partnership with Mercedes, McLaren is the only team changing power units over the winter ahead of the 2021 F1 season, creating added significance to its fire-up event.

The MCL35M was brought to life on Tuesday at McLaren’s factory in Woking, with the team sharing a video of the process via its social media channels on Wednesday.

Despite teams carrying over their 2020 chassis into the upcoming campaign, McLaren’s switch to Mercedes engines means it has had to design “essentially a new car” for 2021, having been forced to use both its permitted development tokens on the major change.

"Whereas every other team will carry over most of its car from last year into this year, our switch to the Mercedes power unit means that's not the case for us," McLaren production director Piers Thynne explained.

"It's driven a huge amount of change and, essentially, we've been building a new car. The number of new parts on the MCL35M is about the same as when we built the MCL35.

"The back of the chassis and gearbox bell housing around the engine have changed significantly to adapt to the new power unit.

"Changing power unit greatly alters the architecture of the car and the way everything is packaged, so the entire cooling layout and all the pipework, be that for fluid or air, has changed, along with all electrical harnessing and control boxes.

"There are some significant elements of carryover as we enter the cost cap,” he added.

"The FIA created a list of Transitional Carry Over (TCO) components that are outside of this year's cost cap. These are parts that can be used in 2021 if they were run on last year's car.

"We've pushed these TCO regulations to the absolute maximum to allow us to carry over as much as possible, such as gearbox internals and some suspension components, and therefore not have to use a portion of our 2021 budget on their design and production.”

McLaren will field a revised driver line-up consisting of Lando Norris and Daniel Ricciardo for the 2021 F1 season. Pre-season testing taking place on 12-14 in Bahrain, two weeks before the season-opener in Sakhir.

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