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WEC Silverstone/Spa Review, Le Mans Preview

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The casual observer may be tempted to look at the results of the two six-hour races held this season ahead of the Le Mans 24-hour race and conclude that Audi will stroll to victory there once again. The reality, of course, is not so simple. Why not? Well, let us look at those two races in a bit more detail and see what conclusions can be drawn.

Having won the 2014 World Endurance championship and retiring from a strong lead at Le Mans last year, many expected Toyota to start as favourites for the 2015 season. However, two races in, it is clear that the Japanese manufacturer will arrive at Le Mans as something of an underdog.

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Toyota’s engineers were not idle over the winter, however. Developments were made which led to improvements in lap times both at the Prologue at Paul Ricard and also at Silverstone. Despite the decision to remain in the 6MJ category, those improvements were of the order of 2%, around 2.3 seconds per lap at Silverstone compared to 2014.

Out of the 377 racing laps at Silverstone and Spa, Porsche has led more than any other car: a total of 191 laps. The fact that such dominance has not been converted into a win (yet) must surely sting, and yet the Weissach engineers are learning fast. A podium at Silverstone in 2014, and a win at Interlagos at the end of their comeback year have raised expectations for 2015 to a very high level.

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Meanwhile at Ingolstadt (or should that be Neuburg, now that Audi has installed the Joest Racing Audi Sport part of the operation down the road a few kilometres), the midnight oil has been burned throughout the winter developing the R18 e-tron quattro into a lighter, more agile beast, using an upgraded hybrid system.

The main talking point following two rounds of the 2015 World Endurance Championship has been the improvement in lap times since last year. With no fundamental change in the regulations, it really is remarkable how much progress has been made in just twelve months. Here is the data from Silverstone and Spa:

Silverstone 2014
Manufacturer Sector 1 Sector 2 Sector 3 Lap Top Speed
Audi 31.851s 43.693s 29.028s 1m 44.572s 278km/h
Porsche 31.869s 44.826s 29.232s 1m 45.927s 297km/h
Toyota 31.622s 44.252s 29.002s 1m 44.876s  288km/h

 

Silverstone 2015
Manufacturer Sector 1 Sector 2 Sector 3 Lap Top Speed
Audi 31.290s 42.225s 27.954s 1m 41.469s 273km/h
Porsche 31.538s 42.724s 28.119s 1m 42.381s 295km/h
Toyota 31.486s 42.851s 28.213s 1m 42.550s  281km/h

 

Spa-Francorchamps 2014
Manufacturer Sector 1 Sector 2 Sector 3 Lap Top Speed
Audi 34.661s 56.192s 31.539s 2m 02.382s 302km/h
Porsche 34.057s 57.559s 30.717s 2m 02.333s 310km/h
Toyota 34.158s 57.030s 30.973s 2m 02.161s  304km/h

 

Spa-Francorchamps 2015
Manufacturer Sector 1 Sector 2 Sector 3 Lap Top Speed
Audi 33.681s 54.588s 30.398s 1m 58.667s 304km/h
Porsche 32.934s 55.387s 30.125s 1m 58.446s 314km/h
Toyota 33.926s 55.655s 30.697s 2m 00.278s  300km/h

 

The data here is derived from taking the average best 20% of race times for all cars competing from each manufacturer, which is the fairest way that I could think of doing it, removing the effect of different drivers, weather conditions, numbers of cars in a team and the configuration of those cars. If one then takes an average of all the averages (always a bad thing, as my maths teacher used to tell me), then you get the overall result that Audi has improved by 3.0%, Toyota by 1.7% and Porsche by 3.1%.

Perhaps equally interesting though is the lack of an equivalent increase in the top speeds: note that the basis of these is to take the average of the top ten speeds recorded. It would seem that the claim of many of the manufacturers that they have been striving to reduce drag is not backed up by the evidence. Better laptimes come from increased downforce and that leads to more drag.

Another view of this is that fuel consumption is so critical, that the engines simply drink more fuel as they are pushed faster, so that the restriction on fuel flow merely places a cap on the top speed. In the overall scheme of things, this is probably not a bad thing.

Talking of fuel consumption brings me on to consider the fuelling strategy that we might expect at Le Mans. The regulations are written in such a way as to define a minimum consumption that each of the LMP1 hybrids must achieve. As a consequence, the stipulation of the fuel tank size (68.3 litres petrol, 54.2 litres of diesel) defines an expected number of laps that each car will achieve.

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The problem in working this out, is that in real life, there is always a little unused fuel in the tank, due to fuel pumping issues and the length of the fuel feed pipes: minimising this volume is one of the dark arts of endurance racing. However, by making assumptions, it seems clear that Porsche will be able to do 14 laps between fuel stops, and Audi and Nissan only 13. Toyota, I reckon, is right on the edge of 14.

This raises the strategic question of how critical being able to go that extra lap is. In fact, if you can lap at anything over about half a second per lap quicker, then by pitting every thirteen laps, you’ll get to the finish before someone who is pitting every fourteen laps, but at a slightly slower pace. So if Toyota is unable to get the last litre(s) of fuel to make fourteen laps, it won’t be the end of the world for them

The key factor in Audi’s win in the Six Hours of Spa-Francorchamps was its ability to use the six sets of tyres allocated more effectively than Porsche. The pace at Spa was so fast, that seven pit stops were required to get to the flag. That meant that two of the stints need to be on used tyres; and having been subjected to the strain of being on a 919 Hybrid for more than three-quarters of an hour, Porsche’s Michelins would not provide sufficient grip for their drivers to maintain their lap times.

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At Le Mans, in contrast, there is no restriction on the number of tyres used, so if Porsche is hungrier than Audi for tyres, it will not be so serious. It is a similar dilemma to the one facing Toyota on fuel: do Porsche go faster and change tyres more often? Or drive more carefully to make the tyres go further?

Even though the track surface at Spa is very different from Le Mans, the evidence from Belgium suggests that Audi will quadruple stint tyres at Le Mans. Even if Porsche can only double stint theirs, if they can lap just three-quarters of a second per lap faster than Audi, then Porsche will have time to change tyres and still complete the greater distance over 24 hours, assuming that all else is equal.

Ahead of Sunday’s test on the full 13.629 km circuit, the focus will therefore be on the relative lap times as well as the absolute. Not just over a single lap, but over a whole stint. What will be difficult to ascertain is when worn tyres are being used.

Back in 1971, Pedro Rodriguez put the Gulf-sponsored Porsche 917 (with a number 18 on the side) on pole position at Le Mans with a time of 3m 13.9s.

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This compared to the pole position time from the previous year of 3m 19.8s. Last year, pole position was two seconds slower than that – and frankly, I think that Rodriguez’ record is safe. However, in 2008, Stéphane Sarrazin took pole position for Peugeot in a time that was 7.8s faster than the previous year. If a Porsche can manage that kind of improvement this year, then I might yet be proved wrong.

One final thing to look out for during the test day: all of this analysis assumes that on track, the cars won’t get in each other’s way. Being able to negotiate traffic and overtaking rivals will be critical to winning this year’s race, so it will be interesting to watch the track action – even though it is only a test!

Paul Truswell