Honda is running a revised final 2016-specification Formula 1 engine at this week's second pre-season Barcelona test – with McLaren set to evaluate tweaked bodywork to help improve cooling too.
Having trialled several components during the opening test last week, and subsequently completed two filming days, Honda has settled on the configuration that is undergoing this week's FIA homologation process.
That version of the power unit will be run at Barcelona this week, and features different parts to the experimental components evaluated during the first test.
As part of a winter effort to make its compressor and turbo larger, Honda's 2016 power unit is slightly taller than last year's version – although retains as much of the compact packaging as possible.
However, in a bid to help improve the cooling characteristics of the internal combustion engine and energy recovery components, McLaren is evaluating a tweaked engine cover solution to improve airflow.
Although this move would appear to go against the famous 'size zero' concept that McLaren has long favoured, the team has also insisted that its aerodynamic preference would never force Honda to compromise its engine demands.
Speaking last week about the 'size zero' concept, racing director Eric Boullier said: “The size zero concept is to give the aerodynamicists of McLaren as much space as possible to create and to invent downforce.
“We never ever impose anything on Honda. They do what they want.
“If they come with an engine [that is bigger] we have to accommodate this in our size zero – which will not be a size zero anymore.
“There is absolutely no constraint, and if we keep this concept because we are happy with it, we believe it is a concept that will allow us to catch up faster than others.”