Honda finalising how to use its F1 engine development tokens

As the new power-unit manufacturer on the grid, Honda has been allocated a smaller number of tokens for this season compared to Ferrari, Mercedes and Renault who are now into their second year with the 1.6-litre V6 turbo-charged units.

With only nine at its disposal, Honda has to plan very carefully when and on what to use the tokens to try and improve performance for McLaren.

"We don't have the complete plan yet as to how to use the tokens, which areas and when," said Arai.

"We have already confirmed which areas are the most effective, and I know we are making a plan to apply race-by-race how many tokens we spend.

"One area where we are weak is horsepower - we need more horsepower.

"So one area to use the tokens is combustion, and the MGU-K and MGU-H because energy is a very important part.

"Combustion and energy recovery systems are very important."

Asked as to how that could be achieved, Arai said: "Maybe we need to change the combustion concept, or the turbocharger, or the camshaft, those kind of parts.

"We should try to change the combustion concept because maybe the other power-unit suppliers are always thinking about better combustion characteristics.

"Every day, on the research and development side they are thinking about it, working on or testing a new combustion concept to get more horsepower to immediately apply that.

"Maybe that's the area to use the tokens."

McLaren and Honda enjoyed a relatively successful test at Barcelona on the back of another difficult grand prix weekend in Spain.

Jenson Button described the first 30 laps of the race as 'scary' given the issues he encountered with instability at the rear of the car.

That was at least cured come Button's day in the car on Wednesday, after Oliver Turvey had driven on Tuesday, when he completed exactly 100 laps with no problems, proclaiming there had been a considerable improvement.

Arai confirmed Button and team-mate Fernando Alonso should also experience "more controlled driveability" from the engine for the forthcoming races in Monaco and Canada.