Honda motorsport boss Yasuhisa Arai tells F1i “we need a bigger size of turbocharger”, but adds that the Japanese manufacturer intends to keep a compact engine package overall.

Honda and supplied team McLaren experienced a dismal 2015 campaign in the light of poor power unit reliability and performance.

Part of the issues stem from the constructor’s radical split-turbo design, which has the turbine at the back and the compressor sitting within the ‘Vee’ of the engine. In order to be in concordance with McLaren’s “size zero” philosophy, both components were downsized as much as possible.

The problem is that a smaller turbine generates less power and more back pressure, which ends up penalising the internal combustion engine (ICE) in the higher RPMs. As a result, the MGU-H absorbs less power from the turbine shaft, and is not capable of charging the battery and supplementing the MGU-K.

“The size led to the inefficiency,” Arai confessed to F1i's Chris Medland in an exclusive interview. “The size is small so the engine needed high pressure air. So that means the high rotation - 120,000rpm - is the limitation.”

Asked whether Honda was going to change the layout of the Vee to fit a bigger turbo, the motorsport boss added: “There won’t be such a big change. We’ll still have a compact layout, but I know that we need a bigger size of turbocharger. So keeping the concept but changing the inside of the chamber or making any part smaller is a big target.”

Honda and the other three engine suppliers were initially supposed to have fewer tokens to upgrade their power unit design this season, but a change to the system was ratified following a meeting of the World Motor Sport Council [WMSC] last December.

The rationale behind the decision was to help struggling manufacturers – namely Honda and Renault – make up for lost ground. Arai believes the 32-token allocation gives the Japanese manufacturer enough scope and leeway to turn things around.

“The token system is a good system to reduce the cost because the areas for development are limited. But if you have a big gap it is very difficult to catch up.

“We discussed it with other suppliers and the FIA so this year we have the same number of tokens. I think that's enough for everyone. So now it’s not so difficult to change big items.”

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