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McLaren boss Ron Dennis said it would have been impossible for McLaren to be compete for world championships if it had decided to stick with Mercedes power units going into the future.

McLaren will have exclusive use of Honda power units next year as part of a works deal that will see the team end a 20-year engine partnership with Mercedes. With power units - including the engine, energy recovery systems and energy store (batteries) - now such a major part of a car's performance, Dennis said McLaren could never hope to compete with the dominant Mercedes works team using the same engines.

"The one thing that jumps at you if you look at all the qualifications that we've had this year is the difference between the Mercedes works team and the other teams," he said. "By and large it's always a second and that's putting aside the pace they can generate in a grand prix when they're on the back foot. What that means, in my opinion - an opinion held by many people in our organisation - is you have no chance of winning a world championship if you are not receiving the best engines from whoever is manufacturing your engine.

"A modern grand prix engine at this moment in time is not just about sheer power; it's about how you harvest the energy, store the energy and effectively if you don't have control of that process - meaning access to source code - then you are not going to be able to stabilise your car in the entry to corners, for instance, and you lose lots of lap time. So even though you have the same brand of engine you do not have the ability to optimise the engine."

Dennis revealed that McLaren already has a chassis designed to accommodate the new Honda power unit, but it will not hit the track before the end of the year.

"We are well advanced in a programme that will see us build - it's designed already - and run an MP4-29H, which is a completely dedicated systems development car for the Honda engine. We will be able to do that any time after Abu Dhabi. We don't know when it's going to be, but out of respect for Mercedes it will be after that date."

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