Tech analysis: Why cooling became Mercedes' Achilles heel in Russia

Both Mercedes cars struggled noticeably with overheating issues during the Russian Grand Prix. And although Valtteri Bottas was able to take the win thanks to being in clean air at the front, Lewis Hamilton's woes showed it could have been a different story if Ferrari had been ahead from the start.

The Mercedes situation was not helped by race day being hotter than forecasts had predicted. The temperature swing was enough to tip Mercedes out of its comfort zone, but if the team had not been in such a close battle with Ferrari, would the Brackley-based outfit have been more reserved in its choices?

After all, teams have numerous cooling packages available to them throughout the year, each configuration a compromise based on circuit specificity and temperature fluctuations between qualifying and the race.

Each of these packages comes with its own cooling advantages and aerodynamic drawbacks, as the more you open up the bodywork, the less efficient it becomes - especially at higher speeds.

The rear end cooling package ran by Mercedes in Russia utilised a perforated gurney flap on the trailing edge of the cooling outlets (arrowed).

These gurney flaps are used to help the region create a little more downforce, of which the perforation is present to allow some of the high pressure of the upper surface to bleed into the low pressure region behind, allowing it to operate at a wider angle of attack.

The acceleration of this airflow around the trailing edge of the cooling outlet should also result in a suction effect on the air flowing through the cover, improving the car's overall cooling efficiency.

Mercedes W08 rear end comparison

Photo by: Giorgio Piola

This is with all things being equal though, with this configuration optimised for a certain cooling threshold before being superseded by a larger cooling outlet, such as the one used in Australia and Bahrain.

This larger cooling outlet comprises a revised upper section to the engine cover with cutouts around the upper wishbones and a larger hood over the exhaust - albeit it can be run without the hood, as Hamilton did so in Australia.

Mercedes F1 W08, T-wing

Photo by: Giorgio Piola

The other major cooling solution we’ve seen Mercedes introduce this season is its shark fin cooling chimney (above), which was used in Australia and Bahrain but replaced with a normal shark fin engine cover for China and Russia.

Heat created under the cover is released out the top of the chimney in unison with the rearward cooling outlet, giving much more scope for heat rejection.

Heat soak

Temperature miscalculations aside, there are two other question marks over Mercedes performance in Russia that can be answered by other scenarios that unfolded.

Firstly, we know both Mercedes drivers were said to be struggling with temperature management but it appeared that Hamilton suffered a little more.

This can be partly put down to the Brit running behind the Ferrari cars, whilst Bottas moved along in free air, with the SF70H of Raikkonen creating turbulent airflow that becomes less effective as it passes around and through the W08.

This is a problem that is exacerbated by the 2017 regulations, with the point at which the wake affects a trailing car moved rearward. It's something we’ve noted by the drivers' comments of the cars being less aerodynamically stable as they approach another competitor.

The other issue was the aborted start, prompted by Fernando Alonso’s early withdrawal from the race, which meant car temperatures increased as the Mercedes cars sat soaking it up, waiting for the rest of the grid to form up behind them before doing a second formation lap.

You might argue that this surely affected Ferrari just as much, given its front row lockout, but it appears that the team didn’t suffer from the same cooling miscalculation.