Mercedes' cooling "Achilles' heel" explained

Mercedes was unable to fight for victory in the Austrian Grand Prix because of cooling limitations, which were the results of the compromises implicit in designing modern Formula 1 cars.

Beyond the regulations themselves, cooling has a significant impact on the aerodynamic package, so designs are not only defined by maximising the airflow to radiators.

A lot of the impact rests in the cooling requirements of the powertrain. All powertrain components are designed to work at optimum levels within a certain temperature range. If it's too cold, then the components cannot move as perhaps they should do; lubricants won't be at the right viscosity, and any expected thermal expansion isn't there.

But if it's running too hot, then those components aren't working as efficiently as expected. Furthermore, the materials from which the components are made begin to weaken, and this puts a lot of stress upon them.

For both reliability and efficiency reasons, maintaining the right amount of cooling is paramount.

Inside the car, there are radiators cooling all the powertrain components, lubricants and liquids. To bring them within the working temperature range, teams must delve into the world of thermodynamics to settle on the right mass flow rate of air drawn through the intake systems. Teams must also ship the resulting hot air out the back of their cars once the heat has been exchanged to ensure the high temperatures don't linger within the confines of the bodywork.

This explains the rationale in opening up the rear of the cars when F1 goes to tackle the hotter circuits on the calendar. But few expected Austria to be quite so swelteringly hot; indeed, Mercedes really began to struggle heavily with the conditions last weekend.

Even cracking open the vents either side of the drivers' cockpits didn't quite alleviate the concerns. Mercedes knew that overheating was an inherent issue of the W10, but didn't possess the wider-exit bodywork in Austria as it was blindsided by the conditions.

It emerged that Mercedes didn't have large enough radiators and, although it's a situation that the team has managed to work around, the high temperatures were sufficient enough to demand that the power units be turned down to reduce the heat under the bodywork.

"We knew that it was our Achilles' heel, and we were carrying the problem since the beginning of the season," said Mercedes team boss Toto Wolff after the race.

"We tried to work on mitigating the performance loss, but at the end, it was really painful to watch - cruising and not being able to defend or attack. I think when you look at the positives - we had the car pace, we were running the engine turned way down, lifting and coasting for up to 400m, that's almost having no throttle rolling downwards. And still able to pull in some decent lap times. I think we would have [had] a chance to fight for the win, but we were limited by the cooling problems.

"It was a surprise to see Mercedes struggling with overheating problems. You would have thought that it would have the data, and in turn components, required to be on top of any situation" Gary Anderson

"The next step would have been to remove all the bodywork. So, that was not really an option, because the sponsors wouldn't have liked it! [We were] right on the limit, we couldn't do anything anymore. It was already very damaging for performance, what we did. There was no step left anymore."

Although a fix is being worked on and was already in the works before Austria, Mercedes has scheduled that in for the latter half of the season - where high-temperature venues are more prevalent.

"First of all, I'm really hoping for the typical English weather in Silverstone," added Wolff, "so we can gain a little bit of time to sort our problems out.

"But then there is no question, there is no alternative than to fix our problems for the coming hot European races - Hockenheim and Budapest. There is just no other option."

Gary Anderson says...

It was a surprise to see Mercedes struggling with overheating problems in the Austrian Grand Prix and not have the required bits of kit available to react to this eventuality.

During the aerodynamic research and development programme for a car, the cooling would normally be set at an average of what was required over the past couple of seasons.

If, for example, the average ambient was 30C then your cooling calculations would be based on that as it is a waste of time to finalise your car package with only enough cooling to cope with something like 25C.

It's not as simple as just stuffing in a bigger radiator as the current cars are full of coolers for a wide range of demands - cooling engine water and oil, gearbox oil, hydraulic oil, the MGU-K, engine charge and the battery pack - so there's not much space to add in something bigger.

And bigger is not always better, as designers want to use as little airflow as possible to cool the car. Airflow used to cool the car is wasted for producing downforce, but teams need to be honest and not put themselves at a disadvantage even before the season kicks off.

If the standard aerodynamic package will cope with the cooling requirements for 30C, it's common to also introduce intakes - or more likely exit ducts - to cope with 35C or perhaps even more. These extra ducts will compromise the downforce level, but they will at least ensure you can go racing.

The opposite will also be required if it is a chilly day at Spa, or even Silverstone, so smaller ducts to get the temperatures high enough will be required.

With all of this it is about finding the most efficient way to get the cooling required for temperatures between 20C and 35C+, and then that's the downforce level that a team is left with.

Mercedes has coped with many scenarios over the last six seasons, ever since the introduction of the hybrid power units, so you would have thought that it would have the data, and in turn components, required to be on top of any situation thrown at the team.

Austria proves that Mercedes is capable of getting caught short, and this will give Ferrari and Red Bull encouragement as their engineers will know that for Mercedes to get that extra bit of cooling, it will come at the cost of a small amount of performance.