Thu 20 Jan 2022 08:43:05 CET

FIXME Chapter Editor:Aricus654 has done the 2016 update, this chapter is now ready for proof-reading.

War of the classes

Le Mans isn't just about winning the race overall - it comprises four main separate classes, each entrant fighting for the honours in their respective class, and the competition within each often as fierce as that for the overall victor. The prototype classes - LMP1 and LMP2 - are for cars specially developed for the track only, and the GTE classes - GTE-PRO and GTE-AM - are essentially road cars modified for the track.

LMP1 - Le Mans Prototypes Class 1: a new era - It’s all about the energy consumed

For many years, in order to prevent excessive power development, the rule makers for Le Mans and almost every other motor race on the planet have restricted engine output by limiting the cubic capacity or the number of cylinders, by modifying the size of air restrictors or restricting turbo boost, thus limiting the amount of air (and thus fuel) which could be fed into the engine.

From 2014 in the LMP1 category, these fundamentals radically changed in that the energy consumption of the engine becomes the key factor. Manufacturers can largely build what they want.

There are minimal restrictions on engine size number and turbo boost and in addition the regulations permit up to two energy recovery systems (ERS) per car. These systems recover what would otherwise have been lost energy and allow it to be used to power the car.

However, what the regulations have done is give with one hand and take away with the other.

Depending on the level of energy that a car can recover and use, it is placed into a category that determines how much fuel it is allowed to consume. Fuel flow meters measure the flow and relay the information back to the authorities.

In simple terms, the new regulations challenges entrants to make the best use of a prescribed amount of energy in order to cover the longest distance within a given time – such as 24 hours at Le Mans. This makes the challenge for the cars to be both fast and energy efficient.

Old hands among the fans remember that this concept is not really brand new: in the glorious days of Group C sports car racing there was a regulation which limited energy consumption, everyone got an allowance of 2,140 litres of petrol for the whole of the 24h of Le Mans. Engine constructors had complete freedom, in those days Porsche raced a 6 cyl. flat 3.0 litre Turbo, Jaguar used 7.0 litre V12 normally-aspirated engines, the folks at Mercedes built a 5.0 Litre V8 Turbo and Mazda used a rotary engine. Despite these very different concepts the performance of the competitors was close to each other, competition was fierce and the races were interesting to watch. However, in the Group C days there were no energy recovery systems around and diesel was only used for team trucks, so this rather simple approach worked fine.

From 2015, the differences between manufacturers and privateers has been abolished, and the class is now divided into LMP1 Hybrid (for cars with ERS) and LMP1 non Hybrid (for those without ERS).

Hybrid cars are categorised into four different performance classes, and a maximum amount of energy able to be used is defined for each of these classes. The energy chart below shows the amount of energy allocated to each power train concept, and the associated fuel flow allowed.

LMP1 LMP1 Hybrid
Energy recovery (Megajoule)0<2<4<6<8
Minumim weight855 kg875 kg
Max fuel flow Kg/h (petrol)100.994.391.989.588.5
Max fuel flow Kg/h (diesel)

What this boils down to is that entrants must have optimum control of the car’s fuel consumption, be able to approach the permissible energy limit as closely as possible, and the drivers must exercise an efficient driving style. If the amount of energy available per lap is not fully consumed, it cannot be carried over to subsequent laps and will therefore be lost. Should the prescribed maximum levels be exceeded, the excess consumption must be compensated for within three laps, otherwise penalties like stop-and-go may be imposed.

So effectively, the manufacturer with the most efficient power train being driven by drivers with an efficient driving style will win the race.

All this means that on-board loggers and computers constantly monitor the fuel flow and output of the energy recovery systems, and data is sent real-time to ACO computer equipment which flags any discrepancy to the stewards. What this means is that the teams monitor the car's fuel consumption and if it goes over that allowed in the their hybrid category, then the driver is instructed to recover the discrepancy, by for example, slowing down.

Today’s LMP1 constructors have each taken a different view on what might be the best solution, so similarly to the old Group C we see a variety of extremely different engines and hybrid systems.

Toyota (8Mj category), after winning the the WEC in 2014 and having a very mixed 2015, Toyota have introduced an all new car and gone from 6Mj to 8mj and changed from a 3.4 ltr. V8 normally aspirated petrol engine to twin turbo 2.7 ltr V6 driving the rear wheels together with a hybrid system using energy recovery from the front axle, energy storage is now lithium ion instead of a supercapacitor and drive electric motors on the front and rear axles.

Audi (6Mj category), employ a 4.0 ltr. V6-Turbo Diesel together with a hybrid system recovering energy from the front axle together with lithium ion storage driving electric motors on the front axle.

Porsche (8Mj) have the smallest engine with a 2.0 Ltr. 4-cyl-Turbo petrol engine driving the rear axle in addition to a hybrid system recovering front axle and exhaust energy, which is stored using a lithium ion battery and drives electric motors on the front axle.

The ACO, in their perennial quest to have all cars in a given category going round the circuit with exactly the same lap times (fortunately they have not yet achieved this!!), have defined the principle of “Equivalence of Technology”, and this gives them the ability to balance out the performance between the hybrids and non-hybrids by increasing the performance of the non-hybrids. This EoT is calculated on historical data collected from the fastest car(s) in each technology.

Manufactures must balance all the compromises in their design – the conventional fuel driveline together with the hybrid components including the systems to recover the energy, the storage, and the hybrid drive method and the overall impact these have on the car’s weight as well as packaging and reliability. Conventional wisdom appears to suggest that the more hybrid capability a car has, the faster it is, despite the best intentions of the regulations. In addition, the more efficient the car is, the less refuelling it has to have, so the longer it can stay out on track.

2016 has seen minor changes for LMP1 and 2, many safety related, a few of which are aimed at slowing LMP1 cars and some are in preparation for major LMP2 changes in 2017.

Key 2016 changes:

  • the outlawing of elastic cords attached to the harness shoulder straps
  • the number of rear “Rain/Fog” lamps doubled from two to four
  • wheel attachments are also changing to a system which includes an automatic safety retain of the nut to prevent the wheel from coming off accidentally
  • the minimum weight of the cars is up 5Kg to 875kg for LMP1 Hybrid and 855kg for LMP1
  • a reduction in fuel tank sizes; petrol 62.5 litres with ERS (from 68.3), 67.4 litres with no ERS, Diesel 49.9 litres with ERS (from 54.2), 53.7 litres with no ERS
  • a reduction of energy by 10Mj/lap, (representing a reduction of 7.5% for the faster cars)
  • instantaneous fuel flow reduced by the same proportions
  • ERS output limited to 300Kw for Le Mans
  • additional head protection padding for the driver
  • three different homologated bodywork iterations will be allowed during the season, reducing to two in 2017

The overall aim of the 2016 energy changes are to slow the LMP1 cars by as much as three and four seconds a lap at Le Mans in comparison to the times that we saw in 2015, however, it is likely that the three LMP1 hybrid manufacturers of Audi, Porsche and Toyota may be able to make up some or all of this time by June 2016.

LMP2 - Affordable Competitive Prototype Racing

LMP2 aims to provide relatively affordable sports prototype racing. It is aimed at privateer teams and not manufactures and is becoming very popular. Manufacturers are actively discouraged – “The ACO do not wish to encourage the Manufacturers to invest in LMP2 in any developments which improve the performance of the cars. The main objectives for these cars must be reliability, safety and a low maintenance cost.”

Cars can be open or closed-cockpit designs, and must have fins on the rear bodywork, and have a space for a passenger seat, usually occupied by electronic devices and cooling equipment. Engines are production-based and can be petrol or diesel, either normally aspirated 5.0 ltr petrol or Turbo/ supercharged petrol: 3200cc 6 cylinders maximum.

LMP1 is reserved for professional drivers, and Bronze drivers are not eligible, however in LMP2 the emphasis is on amateur drivers and at least one member of driver crew must be a Silver or Bronze category driver.

Open prototypes are still allowed in this class. LMP2 cars are also heavier than the faster LMP1 category, with a minimum weight of 900kg.

LMP2 - Balance of Performance

The Balance of Performance exists to adjust the relative performance between different cars to maintain competitiveness - in other words, if your car performs consistently better than others in the class, your car will be slowed down by reducing engine power, having additional ballast or by reducing fuel tank size.

2016 Changes

Ahead of major changes being introduced in 2017 (an additional 150 hp and an anticipated four-second decrease in lap time at Le Mans and locked down until 2017), changes for 2016 are mainly limited to reducing cost.

  • The selling price of a new open car must now not exceed €388,500; for a closed car, the maximum figure is €463,500
  • The engine purchase price must not top €86,778, or its rebuilt price €40,500
  • If the engine is leased, the hourly operating cost must be no more than €1,402

The GT cars

The Le Mans GTE class is for production-based cars. The car must have “an aptitude for sport with 2 doors, 2 or 2+2 seats, opened or closed, which can be used perfectly legally on the open road and available for sale.”

The ACO caters for both small and large manufacturers, and differentiates between them. Small manufacturers are those making less than 2000 per year, and one car per month. Their cars are eligible to race once 25 have been made. Large manufacturers must produce at least one car a week and their cars are eligible to race after 100 have been made.

The engine must be used in a production car; while this is usually the engine from the same model road car, the ACO can grant exceptions for the use of engines from other models. With exception for carbon cockpits (not attached to the suspension directly), exotic materials such as carbon fibre, titanium and magnesium are not allowed except for special parts like spoilers or wheels. Engine displacement is limited to 5.5L naturally aspirated or 4.0L turbo/supercharged. (The ACO has previously granted special waivers for Vipers to 8.0L.) The minimum weight is 1245 kg. Cars must have working lights and windshield wipers, in addition to rear-view cameras and use yellow headlights. Four-wheel drive is not allowed, however traction control is.

GTE - Balance of Performance

As with LMP2 cars, to cope with the different makes and models, the Endurance Committee of the ACO uses the Balance of Performance (BoP) which allows changes to be implemented to cars through adjusting the weight, fuel tank sizes engine, aerodynamics and restrictors to ensure that competing cars are within the same performance envelope. As a result of the overwhelming performance of the new Ferrari 488 in the first 2 rounds of the WEC, competitors Ford and Aston Martin have received weight breaks of 20 kg while Ferrari has been given a 10kg increase in minimum weight.

GTE Categories

GTE is divided into two categories: GTE-Pro and GTE-Am which for 2016 will have different technical specifications.

  • LMGTE-PRO - designed exclusively for professional drivers. Cars are current year, or updated to the current GTE Pro regulations.
  • LMGTE-AM - drivers must include amateurs, but can be backed up by up to one professional driver, so a Platinum or Gold driver can be included with one two Bronze or a Bronze and Silver in each line-up. Cars are at least one year old. This was designed to create a second-user market for GT cars. The crew is limited to only one professional driver. The timed laps in qualifying must be made by a bronze driver.

Changes for 2016

2016 will be a transition period with the introduction of new regulations which apply only to LMGTE-Pro cars this year, before being extended to LMGTE-Am in 2017.

The key objective of the new regulations is to increase the performance of the cars relative to the GT3 cars that they compete against in some race series, to reduce cost and improve safety of the cars. Safety is increased through the introduction of a driver escape hatch.

The ACO has introduced a new Balance of Performance envelope for 2016. Manufacturer are allowed to modify aspects of the previously highly regulated production-based aerodynamics in order to fit into the newly defined performance window. Together these changes are likely to result in approximately 20 horsepower increase and 15 kg weight reduction, and better aerodynamics resulting in a two-second per lap decrease in times at Le Mans.

On track, GTE-PRO cars are likely to be noticeable by changes brought about through the freedom of bodywork styling, and their stronger performance.

The 4 classes - overview

The following overview gives just the most basic facts, the exact regulations are very extensive with lots of technical stuff, e.g. numbers about the minimum of road cars produced for the GT classes, size of the wings and others. The complete rulebook can be downloaded from the website. All figures mentioned are maximum values, except the car’s weight of course…

LMP1 Hybrid and LMP1

  • Closed roof sports cars with room for 2 seats
  • 4.65 m length, between 1.8 to 1.9 m width, 1.05 m height
  • Engine size is free for LMP1 hybrid, max 5.5 litres for LMP1; reciprocating pistons only
  • Minimum weight of 875Kg for P1 hybrid, 855Kg for P1
  • Maximum fuel tank sizes: petrol 62.5 litres with ERS, 67.4 litres with no ERS, diesel 49.9 litres with ERS, 53.7 litres with no ERS.
  • Headlights with white beam
  • 14” wheel width, 28” diameter
  • Race numbers in white digits on red background
  • Bronze drivers are not accepted.


  • Open or closed roof sports cars with room for 2 seats
  • Production based engines: 5.0 ltr. atmo engine (max 8 cyl) or 3.2 ltr. Turbo/supercharged (max. 6 cyl)
  • 4.65 m length, 2.00 m width, 1.03 m height (or 1.05 for 2014-spec cars)
  • 900 kg minimum weight
  • 75 litres fuel tank
  • Headlights with white beam
  • 14” wheel width, 28” diameter
  • Race numbers in white digits on blue background
  • Must include a minimum of one Silver or Bronze driver


  • “Professional” GTE sports cars
  • Minimum weight 1245Kg
  • 4.8m length, 2.05m width (excluding rear-view mirrors)
  • 5.5 ltr. atmo engine or 4 ltr. Turbo
  • 90 litres fuel tank
  • Headlights with yellow beam
  • 14” wheel width, 28” diameter
  • Carbon brake discs
  • Race numbers in white digits on green background
  • The driver line up is free


  • “Amateur” GTE sports cars
  • Specification same as old GTE-PRO
  • The car must be at least one year old
  • Race numbers in white digits on orange background
  • At least one bronze and one silver or bronze rated driver in the team, only one professional driver from Platinum or Gold class

Leader Lights

Leader lights at the Rollcentre PescaroloIn 2007 the A.C.O. introduced the “leader lights” system. Each car must have 3 LED lights mounted on both sides; these lights have different colours for each class:

  • LMP1: red lights
  • LMP2: blue lights
  • LMGTE-PRO: green lights
  • LMGTE-AM: yellow lights

The leading car of each class will show one light switched on, the second place car two lights, the third place car 3 lights; if no lights are burning then the car is fourth or further down the order. These “Leader Lights” will help trackside spectators follow the progress of the race, especially at night or in poor visibility. This system was developed and first introduced by the organizers of the American Le Mans Series in 2002 with the original idea coming from an American race fan. It reloads at the timing line so it is basically the previous lap position that one is viewing.

ca_guide/war_of_the_classes.txt · Last modified: 2016/06/05 10:58 by werner

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