Mercedes' performance in Austria was compromised by the fundamental design of its W10 and its cooling system which was very much on the edge in Spielberg's scorching temperatures.
The Silver Arrows squad was inflicted its first defeat of the season last weekend, with Valtteri Bottas and Lewis Hamilton finishing respectively third and fifth at the Red Bull Ring.
In Mercedes' usual post-race Pure Pitwall video, trackside engineering director Andrew Shovlin revealed that the cooling system of its 2019 contender - which Mercedes boss Toto Wolff has called the 'Achilles' heel' of the W10 - had simply "under-delivered" in the hot temperatures.
"Fundamentally the car doesn’t have big enough radiators," said Shovlin. "And that’s something that we were a bit optimistic with how much we could get out of the cooling system.
"It’s under-delivered to what we hoped we could achieve, and it’s meant that we are carrying this issue where in the very hot races we will be struggling to keep everything cool enough – principally to keep the power unit cool enough that we don’t do any damage to it.
“You can increase the amount of cooling you get out of the car by opening up the bodywork exits," Shovlin added.
"In Austria it was 35C degrees, that actually put us at the upper end of what we could achieve just by opening the car up.
"So, we were on limit. When you get to that point you are really limited in your options."
To protect their power unit in the hot environment, Bottas and Hamilton were forced to make extensive of the 'lift-and-coast' process for "around 400 metres per lap", or 10% of the track's layout.
"That is why they were so compromised on performance," Shovlin said.
"You can also turn the engine down a bit, then it will generate less heat, but you’ve got less power and you are slower on the straights. So, it was definitely a significant limitation in Austria."
While Mercedes' cooling issue is linked to the fundamental design of its W10, the German outfit has been working on solutions to alleviate the problem in the future.
"We are working on systems – we were working on them before Austria – to try and improve this problem and we should be in a better position.
"But, it all really goes down to the fundamental design of the car, where in the push for very, very tight packaging, we have ended up being under-cooled overall."
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