The Austrian Grand Prix turned out to be an extremely difficult one for all Renault powered runners, bringing to light more public frustration from Red Bull Racing's team principal Christian Horner. But is there really a problem with the Renault engine?
It's particularly interesting to observe that at a fairly similar power track that is Circuit Gilles Villeneuve, it was exactly Red Bull Racing that took the top step of the podium. There, Daniel Ricciardo seemingly had no trouble finding pace and clearly confirmed the trend that Red Bull Racing was becoming the best team behind the Mercedes works team.
Renault introduced several new parts in Canada albeit most of them aimed at improving reliability, introducing software and improvements to their diagnostics to prevent issues like the MGU-H and exhaust failures that happened in Monaco. They were well needed, knowing that Montreal was the toughest challenge on the engines so far this season. The company also mentioned that energy recovery from the MGU-K is limited at Montreal, hence focusing on the MGU-H to recover energy through the exhaust gases.
Arriving in Austria, teams had much less accurate simulation data following a string of 11 years without an Austrian GP on the calendar. The track near Spielberg is however known to be power sensitive with around 50% full throttle on a lap. The small number of corners again made it difficult to get a lot of energy recovery under braking, hence also requiring engine suppliers to focus on the MGU-H to charge the batteries.
Even despite all these similarities, all Renault runners had considerable trouble keeping up with the Mercedes cars and were also comfortably beaten by Alonso, the fastest of the Ferrari powered cars in Austria.
But is it down to Renault?
It is, but it's unlikely to be the only reason. Focusing on power, it's good to have a look at the top speeds at the end of each sector, showing clearly that the Mercedes runners had an advantage - as well as in Canada.
Averaging the top speeds of the two fastest cars for each engine supplier, we get the following result (in km/h).
Note that S1 is the point on the straight between turns 1 and 2, just before braking for turn 2. S2 lies halfway between turns 5 and 6, a slower section of the track emphasizing grip and aerodynamic downforce. S3 is obviously the finish line. T is the speed at the speedtrap, located just ahead of braking for turn 3, recorded during qualifying.
It's immediately obvious that Ferrari and Renault are very closely matched when it comes to top speeds while Mercedes is quite a bit ahead. At S1, the difference is around 3.7% and at the speed trap 2.2%.
So what was so different in Austria that made Renault struggle more?
The first important difference to consider between Canada and Austria is the nature and the number of the corners. The Montreal circuit features several medium quick chicanes, allowing Red Bull to make use of its apparently strong chassis and aerodynamic properties to stay ahead of the pack. Spielberg, in contrast is notorious for being less of an aerodynamic differentiator and instead puts an even stronger emphasis on traction out of slow corners. This obviously plays into the hand of stronger drivetrains.
Secondly, both Renault and Mercedes have said that MGU-K energy recovery at Spielberg is more limited than in Canada. With such limitation, we can assume that each power has the potential to regenerate a similar amount of energy from braking during a lap around the Red Bull Ring. Needless to say, the difference in potential power - depending on the exact power unit mapping - then comes from either the internal combustion engine, its turbo, or the efficiency of the MGU-H.
Clearly, the turbo is playing a considerable role here, especially because Spielberg is about 700m higher above sea level than Montreal. This means that, while the engine itself does not really suffer, the turbo spins at a much higher rate to compensate for the low ambient pressure – very close to the hardware limit.
Whatever the truth, and surely the engine developers have figured it out for a long time already, the Austrian Grand Prix may well have exposed the weakness of Ferrari and especially Renault in that their turbochargers may be less conveniently sized than the ever so dominant Mercedes power unit. Sadly for them, if hardware really is the issue, there's little to do but to start investigating how to have a better unit next year, as changing to a different turbocharger only for performance reasons is not allowed during a running season.