The Japanese manufacturer used up its remaining development tokens at the Russian Grand Prix to trial some new updates in first free practice.

Those improvements were encouraging, with sources suggesting that they delivered a step of 20bhp and should produce even more power once mapping has been optimised.

Describing the Russia upgrade as "very positive", McLaren racing director Eric Boullier said: "All the expectations we could have picked on the data and dyno measure worked as planned.

"So we introduced this engine for this track layout that is not suiting our package this year, and will save the mileage for the USA.”

Deployment key

Honda's focus for the winter will now be on improving energy storage and deployment – which remains the area where the biggest performance deficit is.

Honda motorsport boss Yasuhisa Arai told Motorsport.com: “Regarding the internal combustion engine, we feel there has been good progress – but on the track it is still hard to see.

“Still we have the deployment issue, so total car performance is not enough.”

160bhp recovery

The current regulations mean that engines can produce up to 160bhp through energy recovery on the straights.

Honda's power unit is not yet capable of delivering it for a full lap at all tracks – which means there are often times when its drivers face a big dip in horsepower before the braking zone.

Fernando Alonso and Jenson Button have both been clear that it is the area of biggest concern for them, and Honda knows where its improvement focus must be.

“It is the priority above everything else to fix that, but we cannot really say how much we will improve,” said Arai.