Race charts analysis for the 24 Hours of Le Mans 2015

A couple of weeks ago I tinkered with lap time data for the 24 hours of Ascari; now it is time to do the same with data from the 24 Heures du Mans, the world’s oldest active sports car race in endurance racing.

Le Mans stands for passion; it was in the 1970’s film that Steve McQueen uttered these words:

Lot of people go through life doing things badly. Racing is important to men who do it well. Racing is life. Anything that happens before or after is just waiting.

Here, I will use the data from Al Kamel Systems to get some insight into the 2015 24 Hours of Le Mans.

LM P1

“LE MANS” PROTOTYPE 1 is the premier category with two sub-categories: Hybrid —with energy recovery system (ERS)—, and with no ERS reserved only for privateers. Engine is free except following restrictions:

  • Only Petrol or Diesel 4 stroke engines with reciprocating pistons are permitted.
  • Engine cubic capacity is free for “LM” P1-Hybrid cars
  • Engine cubic capacity must not exceed 5500 cm3 for “LM” P1 cars.

This allows manufacturer teams adopt absolutely different approaches to the race. Porsche opted for a 2.0 litre direct-injected turbocharged V4 engine with lithium-ion battery for energy recovery in mid-mounted longitudinal configuration; Audi has a 4.0 litre V6 turbodiesel, mid-engined, longitudinally mounted; Toyota uses a 3.7 litre 90-degree V8 normally aspirated mid-mounted longitudinal configuration; and Nissan is trying to revolutionize the race car concept with a 3.0 litre direct-injected twin-turbocharged V6 engine in a longitudinal front mid-engine configuration.

Porsche, despite such a small engine block, takes advantage of the 8 MJ class (Watkins, 2015). Why is it an advantage? The FIA limits the released energy and petrol energy per lap by imposing a set of allowances for each of the classes in the 2015 Technical Regulations for LMP1 Prototype. The other manufacturer teams opted for a different subclass each: Nissan, 2 MJ; Audi, 4 MJ; and Toyota, 6 MJ.

  No ERSERS options
Released EnergyMJ/lap02468
Electric Motor Efficiency85%0.01.73.45.16.8
Petrol EnergyMJ/lap157.2147.0143.3139.5138.0
Petrol Efficiency30%47.244.143.041.434.5
Total Useful WorkMJ/lap47.245.846.447.048.2

In the table above I show the energy per lap allowance as well as the estimated useful work out of an electric motor (~85% efficiency) and a petrol engine (~30% efficiency). Thus, although the larger ERS option gets to use less petrol energy per lap, the better efficiency of electric motors amply compensate for the difference so that there is more “estimated” useful work. Apparently, the goal per mega-joule of additional hybrid power is to create a lap time 0.5 seconds advantage at Le Mans. On the other hand, because of the way the balancing works, a 2MJ Diesel is only equivalent “roughly” in terms of lap time/kinetic energy to a 4MJ petrol.

Did this theoretical advantage show on track? Porsche won the race, though closely followed by Audi. Toyota was far from the winning pace; although they improve with respect to last year’s car, it was not enough. And Nissan had lots of trouble with their new race car concept; they didn’t engage the hybrid system for reliability reasons.

The following plot shows difference to the average pace of winning car #19 driven by Bamber, Hülkenberg, and Tandy. A grate fate, considering that none of them is a regular driver at Porsche’s Endurance venture.

This historic deed its first steps during the night. Hülkenberg was the driver behind the steering wheel key in taking the car from 4th to lead through very quick pace and smart strategy during the safety car and barrier repairs in the middle of the night.

The #19 took the lead on lap 129, and after a few reshuffles through pit stops, lead the race from lap 253 to the flag. Although, as in F1, most position changes took place during pit stops, not on track, what does F1 need to learn from WEC?

While the focus was on Hülkenberg, his team mates fared equally well, when not better than the German. The following box plot compares the lap times of all Porsche drivers at the circuit of La Sarthe. Bamber and Dumas were the most consistent drivers; while Webber had to deal with a stop and go penalty and several safety cars tarnishing his plot.

LM P2

“LE MANS” PROTOTYPE 2 (LM P2) is a racing car with no production minimum required destined only to teams independent of manufacturers and/or engine suppliers. This is by far the category with the largest entry list.

Total domination. Team KCMG took hold of the lead from lap 9 onwards; though not exempt of problems, towards the end of the race, their two lap lead evaporated resulting in the battle for second place in class finishing on the same lap as the leader.

But KCMG’s race was not as remarkable as JOTA Sport’s. Having won the LM P2 category in 2014, JOTA finished close runners-up in this year’s gruelling event. That after falling to the last positions during the first hours. A 10 minute gap to the lead shrunk to less than 1 minute thanks to a lightning pace during most of the race.

Thiriet by TDS Racing were the only clear contenders for the victory until an incident with #99 Aston Martin shattered their chances.

LM GTE Pro

The “Le Mans” Grand Touring Endurance car (LM GTE) is a car which can be used perfectly legally on the open road and available for sale such as the Corvette C7.R that won this edition against Porsche and Aston Martin. After starting from P10 in the GTE category, the #64 benefited from issues in the rest of the teams.

It was a close battle with the #51 until the Ferrari succumbed to gearbox issues at lap 309, so close to the finish. Although AF Corse was able to repair the #51, by that point had lost far too much time finishing third in class and 5th of the GTE’s. The sister car, the #71 AF Corse Ferrari, inherited second place five laps behind.

LM GTE Am

In this group only cars having 1 year old or fully in compliance with the specifications of the previous year car are admitted. Another requisite is that a crew of 2 or 3 drivers must include at least 1 Bronze and 1 Bronze or Silver driver.

The Aston Martin #98 was leading the race with a comfortable gap over the second classified until, at just 45 minutes to end the race, Dalla Lana lost control and hit the guardrail in the Ford corners. This gave the victory to Ferrari #72 reminding us all that nothing is decided up until the chequered flag is waved.

The other leading actor in the GTE Am category was the Dempsey-Proton #77. The Porsche took 2nd in class after winning the battle with the Ferrari #62 of Scuderia Corsa. The battle for third in GTE Am was a back-and-forth affair between Townsend Bell for Scuderia Corsa and Patrick Dempsey for Dempsey-Proton Racing, with either Bell or Dempsey holding third depending on when they were due to pit. Ultimately, the battle was decided in the final hours when Bell spun at Mulsanne Corner while on a par with the Porsche.

Competition is tough; and in the 24 Hours of Le Mans, more than anywhere else.