Last month, Audi was beaten to victory in the Le Mans 24 Hours for the first time in six years. Motorsport.com's Sam Smith spoke exclusively to Audi's leading engineer Leena Gade.
A combination of circumstances contrived to blunt Audi's attempt at a sixth consecutive Le Mans 24 Hours victory last month.
That is the opinion of Leena Gade, engineer of the No.7 Audi Sport Team Joest entry which initially appeared to be the key contender to challenge the victorious No.19 Porsche 919 Hybrid.
Speaking exclusively to Motorsport.com, Gade – who engineered victories for Audi in 2011, 2012 and 2014 – catalogued the challenges faced by Audi from the start of the 83rd Le Mans 24 Hours, a race in which it knew that only perfect reliability and its famed strategic nous would harness a win.
Temperatures were key to victory
Quirky temperatures at Le Mans this year laid favourable foundations for Porsche to ward off an Audi attack as the dusk to dawn portion of the race played out.
Audi, like all of the manufacturer teams, get detailed forecasting of the track and ambient temperatures from Michelin ahead of the race. This information is then processed by the team in order to pick the best tyre compounds for the event.
A broad band of temperature is always accommodated for at Le Mans, but this year's race turned out to be warmer than initially forecast triggering fluctuating conditions for the tyres and the energy retrieval systems.
"When darkness fell it was warmer than previous years and what we thought it would be before we got there. It never really went below 17 or 18 degrees," said Gade.
"It took us a little bit by surprise and we were expecting it to get a little cooler. We have a cross-over temperature for a different compound of tyre but it just didn't get cold enough for us to use this. It was clear we had to stay on the compound we started the race on."
The Audi's got slower compared to the Porsches as the sun went down and even though they were comfortably quadruple stinting their Michelins, there was no answer to the pace of the Porsches, particularly the No.19 car in the hands of Nico Hulkenberg, Nick Tandy and Earl Bamber.
"Ideally we wanted to go for five stints on the tyres but it was not always an option," continued Gade.
"You have to weigh-up the degradation of the last (fifth) stint versus the time for a tire change."
The warmer than anticipated temperatures may also have factored in to as yet un-diagnosed issues that could have affected the Audis power. It was noticeable that all of the Audi's pace dropped off in the night running, especially in sector two which comprises the Mulsanne Straight, where power is everything.
"We have done a lot of performance analysis since the end of the race and it is still an open-ended question," Gade said at the time of this interview (held on June 25).
"We need to still bottom-out what we were affected by, as it was clear the Porsches didn't get slower in the same bracket that we did. Everyone got slower at night but our delta was bigger. There is more than one factor; temperature is only one part of it. We have an idea of where the rest could lie but we need to look at the data more to find it."
Porsche fuel strategy surprised Audi
Porsche's initial strategy of going 13 laps on fuel surprised Audi, who believed that their rivals would choose to go 14 laps of the La Sarthe track on a tank of fuel.
Porsche went for 13 laps to save weight and also to save refuelling time at the pitstops.
"We could only ever do 13 laps because that is how we have been engineered by the regulations," said Gade. "We don't have a choice and you don't go for twelve unless you have a massive advantage. It originally surprised us that they didn't go for 14 laps but you can see why they opted for this approach."
The decisive period between 11pm and 5am saw Porsche take the initiative, and it soon became evident that their stint pace was better in relation to the Audi R18 e-tron quattros.
"What was apparent through the night was that if you look at the lap times of the Porsches, the lap times were not massively off what they had been doing in the daytime, while we were a good chunk off ours." said Gade.
"We're not really certain why, it could be temperature or grip related, we can see some trends but nothing definite. We also had differences between our three cars."
Motorsport.com understands that Audi has an initial and preliminary report on its performance via data sensors, TV footage and driver feedback completed. A more detailed summary is also being considered and evaluated at its headquarters in Neuberg, Germany.
Engine cover problem had major repercussions
The No.7 Audi had early setbacks in the race including a puncture suffered by Andre Lotterer and then a drive-through penalty incurred by Marcel Fassler for a Slow Zone infringement.
A slight excursion for Benoit Treluyer, at the exit of the Esses before Tertre Rouge lost little time, but added to the difficult start.
As ever though, Audi was still in the hunt on Sunday morning. But any late race challenge on Porsche ended at just after 7am. The loss of part of the No.7 Audi R18 etron quattro engine cover on the exit of the Porsche Curves ceased any notion of catching their competitors.
"We are still investigating it," confirmed Gade. "It wasn't just a simple case of the engine cover failing, it caused us other problems and we were stopped for seven minutes.
"Ultimately any problem like this is going to put you out of contention, except for last year when everyone had issues and were in the pits. When the lead car doesn't have a problem, you are not going to win the race."
The general feeling, even within the Porsche camp was that the 919 Hybrids would at least hit one time-consuming problem. They didn't.
This, combined with the 11pm-5pm pace of the No.19 car, ensured Porsche returned to the winners' circle, as a factory entity, for the first time since 1998.
For Audi, the debriefs will go on, to ensure maximum understanding and prevention of the issues it faced and to set it motion the best possible chance of a 14th victory next year.