A cooling issue would be the origine of the lack of pace of the new Mercedes car.
Ross Brawn ensures he understands the current performance limitation and his team is working on solving it.
"The biggest challenge for us so far has been a cooling problem," said Ross Brawn.
"The short-term modifications that we made to the launch-specification car cost a reasonable amount of performance.
"The solution has been incorporated into the bodywork design for our upgrade package and will recover that performance before the first race."
The director added that the new car was meant to be significantly improved before the beginning of the season.
"Our intention was always to launch the car in a fairly basic specification to allow more time to focus on the upgrade package. This inevitably means that we look further off the pace than people might expect."
Ross Brawn ensures he understands the current performance limitation and his team is working on solving it.
"The biggest challenge for us so far has been a cooling problem," said Ross Brawn.
"The short-term modifications that we made to the launch-specification car cost a reasonable amount of performance.
"The solution has been incorporated into the bodywork design for our upgrade package and will recover that performance before the first race."
The director added that the new car was meant to be significantly improved before the beginning of the season.
"Our intention was always to launch the car in a fairly basic specification to allow more time to focus on the upgrade package. This inevitably means that we look further off the pace than people might expect."