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Le Mans Prototype

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The Le Mans Prototype (abbreviated to LMP), is a class of sports car racing vehicles specifically designed for endurance racing. The most representative LMP race is the Le Mans 24 Hours. These cars rely heavily on aerodynamic devices such as diffusers and rear wings to achieve their intended corner speeds. Except for Formula One, these cars themselves are considered to be the most expensive in the world as they incorporate an array of cutting-edge technology. Estimates of the cost to design, develop and manufacturer these cars have run into millions of dollars. LMPs have no pretense of being related directly to any road going car, they are pure-bred race cars differentiating themselves in this way from the GT subclasses.

Contents

History of the LMP Class


The current LMP class was introduced in 1995 as the successor to the Group C class that had emerged in the 1980s. The "C" in "Group C" might as well have stood for "Consumption", as performance was primarily regulated by fuel consumption. The method used was to limit onboard fuel capacity to 100 liters and restrict cars to 5 pitstops for 1000 kilometer events and 25 pitstops for 24 hour events. Unlike the LMP cars, Group C cars were less heavily regulated: aerodynamic and engine development were virtually unlimited. Group C cars are still faster than even the most advanced LMP cars, but their extreme speeds became dangerous for drivers as developments continued.

The 1989 Sauber C9-Mercedes reached a top speed of about 400 km/h (250 mph), prompting ACO to add two chicanes on the Le Mans straight to lower top speed and subsequently replacing the Group C class with World Sports Cars. A former Group C car could win in Le Mans in 1994 again, with victory going to a Dauer-Porsche 962LM which was modified for road use and entered as a GT. As of 2005, no international races allow Group C cars, but the Group C formula and its North American counterpart, the IMSA Grand Touring Prototype (GTP) class remains a popular presence at councours and vintage racing events.

Top speed plays an important, but not decisive role in victory at Le Mans. Throughout Le Mans' long history, the winners have not always been the fastest machines. In the 1960s, for example, the first Ford GT40s were designed to be fast but soon after, Ford realized that speed could not compensate for a lack of reliability. These cars were forced to retire after just 3 hours of racing. The revised Le Mans-winning Ford GT40s were built for reliability and speed. Similarly, the Audi R8, which won many Le Mans in recent year was typically not the fastest car on the track from a top speed standpoint, though its lap times were the envy of all. Part of the R8's success stemmed from its modular "Lego" design that allowed parts (namely the entire rear end) to be quickly changed. Starting in 2005 the ACO wrote regulations to dissuade that trend with rules stating that the original gearbox must remain the same throughout the race.

LMP Subclasses

There are, today, two subclasses within the LMP class:

  • LMP1: Large, open and closed prototypes with room for two seats and a minimum weight of 925 kg (1982 lb); engine displacement is limited to 6000 cc for naturally aspirated engines and 4000 cc for supercharged or turbo-charged gasoline engines and 5500 cc for supercharged or turbocharged diesel engines. The number of cylinders in the engine is not governed. Vehicles in this class are considered the most advanced in Le Mans, and thus in the world of sport cars. Every overall Le Mans winner since the introduction of the LMP, prototype or sportscar classes in the 1960s has been a member of these classes except the 1979 winner Porsche 935 which was a Group 5 (racing) GT based on the road legal Porsche 911
  • LMP2: This class shares many specifications with the LMP1 class. However, the minimum weight allowed is 775 kg (1652 lb), (the previous minimum was 675 kg (1487 lbs)), and the engine displacement is limited to 3400 cc for naturally aspirated and 2000 cc for turbocharged engines. The number of cylinders is limited to 8. Theoretically, the lower power of the LMP2 cars is negated by the lower weight minimum and they can therefore perform, depending on the circuit, similarly to LMP1 cars. This however has not been the case in recent years due to reliability issues from nearly all LMP2 entries.

For the 2007 season, the ACO has mandated a 1.5% performance advantage of LMP1s over LMP2s and reserves the right make changes to the regulations to ensure that this is the case[1].

Former LMP subclasses included LMP900, LMP675 and LMGTP.


Future developments

However, LMP cars haven't been without their incidents. At Le Mans in 1999, the Mercedes-Benz CLR "took off" and crashed in three separate incidents due to aerodynamic flaws, and the front wheels of a Porsche 911 GT1-98 and a BMW V12 came off the ground at Road Atlanta in 1998 and 2000 respectively. In response to this the ACO introduced regulation changes in 2000 to reduce the prospects of these incidents occurring again. In 2004 the ACO went even further by rewriting the aerodynamic regulations concerning the LMP 1 and 2 category eliminating the flat-bottom aerodynamic regulations for the prior LMP900/LMP675 category and replacing it with a near-spec ground effects tunnel underfloor. The idea was to reduce downforce generated outside of the car's wheelbase. With the old flat bottom/diffuser combination, the rear diffuser started at the rear wheel centerline. Starting in '04 the rear tunnels began 1000 mm in front of the rear wheels. Therefore the primary suction peak generated by the tunnels is well within the car's wheel base and not at the rear axle centerline. This, coupled with a unique "chamfered underflor" which reduces yaw instability, as well as the reduction in rear overhang (to a maximum of 750 mm) and an increase in front overhang (to a maximum of 1000 mm) has reduced the pitch sensitivity of the cars and greatly minimized the chance of a blow-over type accident. And indeed, in 2005 at Monza, Jean-Christophe Boullion's Pescarolo Courage C60 Hybrid spun at high speed following a rear suspension failure with the car subsequently getting backwards. The Pescarolo Courage stayed planted throughout the event without any hint of getting airborne and was an excellent validation test of the revised aerodynamics regulations.

Diesel has become a viable alternative fuel with Audi winning both the 2006 12 Hours of Sebring and 2006 24 Hours of Le Mans with their R10 LMP1. Meanwhile Peugeot will enter their own diesel powered competitor in 2007, the 908.

The ACO announced during the 2006 24 Hours of Le Mans that the regulations for LMP1 will be changed in 2010, to mandate that all LMP1s will be required to have closed cockpits, eliminating the traditional open cockpit design. The LMP1s will also feature smaller rear wings in an attempt to slow the cars down. A key element of the 2010 LMP1 regulations is that the cars will have to feature design cues borrowed from a manufacturer's production cars, thus eliminating privateers and leaving LMP1 to be purely a manufacturers battle.

LMP2s will remain largely the same, with both open and closed cockpit cars being allowed. LMP2 class will also become strictly privateer, which the ACO had original envisioned when it created the LMP1 and LMP2 classes.

List of Le Mans Prototypes

(Note: Some car chassis may have raced in multiple LMP classes through its lifetime or through different setups by teams. These cars are listed in every class they participated in.)

WSC/LMP900/LMP1

LMP675/LMP2

LMGTP

References

  1. 2007 ACO LMP Regulations

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