The 10 Most Important Prototypes in IMSA History

By appearance and performance, prototypes have long set sports car endurance racing apart from other major forms of racing. Arguably they are the world’s most complicated race cars due to their full bodywork, aerodynamics, and weight—plus the obligation to compete for up to 24 hours.

For IMSA, prototypes have played an important role in the sanctioning body’s success. Which ones were the best? It’s unlikely that fans or journalists will arrive at a consensus about which cars had the most compelling design attributes or simply looked the coolest while winning races.

The goal here is to identify which prototypes express not only winning appeal but also have had a significant influence on IMSA history.

Did we miss your favorite? Start the conversation in the comments below:

Porsche 962 – 1984-1993 (IMSA GTP)

Reason for ranking: The original Grand Touring Prototype class took IMSA to new heights of popularity and the Porsche 962 led the way.

When the Porsche 962 arrived in 1984, it was an instant hit.

Led by the Lowenbrau Porsche of Al Holbert and the privateer teams of Preston Henn, Bruce Leven, Bob Akin, Rob Dyson and Jim Busby, the major endurance victories and championships quickly began to roll in. In addition to being one of the first in a series of GTPs produced by auto manufacturers, the adaption by Norbert Singer of his Group C Porsche 956 to the rules of IMSA became a masterpiece of balanced design.

The 962’s longevity was greatly aided by strong replacement chassis built by Fabcar and Jim Chapman.

Key stat: The final Daytona 24-hour win was registered by Reinhold Joest’s team in 1991—seven years after the factory’s white 962 first appeared at Daytona in the hands of Mario and Michael Andretti.

Notable drivers: Al Holbert, Derek Bell, Bob Wollek.

Audi R8 – 2000-2005 (IMSA/ALMS LMP-1)

Reason for ranking: The Audi R8 almost single-handedly sustained ticket sales for the American Le Mans Series for six seasons, because fans loved the car’s winning ways, its charismatic drivers and didn’t care about relatively small starting fields.

The Audi factory teams of Team Joest and Champion Racing had little opposition from others during the LMP-1 era fostered by the American Le Mans Series, making the Audi R8 the most efficient prototype to compete regularly when it came to winning.

Like the Porsche 962, the R8 was perfected as a second-generation car. It followed the R8R, which was difficult to drive and baked its drivers thanks to a front-mounted radiator for the V8 twin turbo. After some wizardry by designer Tony Southgate resulted in side-mounted radiators, the R8 and its crew of stellar driving talent steamrolled the opposition regularly.

The redoubtable Panoz LMP1 Roadster S, for example, only beat it twice. As with the Porsche 962, the popularity of the R8 was boosted by its success at Le Mans.

Key stat: Won 63 races from 79 starts.

Notable drivers: Tom Kristensen, Allan McNish, Dindo Capello.

Cadillac V-Series.R – 2023 (IMSA GTP hybrids)

Reason for ranking: the best of the new GTP hybrids, which promise to revitalize IMSA like their namesakes from the 1980s and 1990s.Of the four new GTP hybrids from Accura, BMW, Cadillac and Porsche, the V-Series.R was the most consistent. And, the only one with a booming, normally aspirated engine.

The Action Express Racing team won the driver’s title and Cadillac clinched the manufacturer’s championship thanks to winning efforts at Chip Ganassi Racing. The latter’s entry at Le Mans finished third after a solid performance, best of the GTPs.

It remains to be seen how things go at the great French race versus the Hypercars seemingly favored by the WEC. But in IMSA, there’s the most excitement about a new class of prototypes since the Ferrari 333 SP first showed up.

Key stat: Although it crashed on the opening lap at Le Mans, the Cadillac of Action Express did not lose any more laps to the leader once it returned to the track following repairs.

Notable drivers: Pipo Derani, Sebastien Bourdais, Renger van der Zande.

Ferrari 333 SP – 1994-2003 (IMSA World Sports Cars)

Reason for ranking: Ferrari’s customer prototype designed especially for IMSA’s new World Sports Car rules helped save the sanctioning body from a post-GTP depression.

Rival competitors were up in arms when the Ferraris arrived thanks to the WSC rule requiring a production-based engine. But the 333 SP’s screaming V12 was derived from F1. Eventually, the same five-valve, 4.0-liter engine showed up in the Ferrari F50. Meanwhile, it was Ford versus Ferrari redux thanks to the Riley & Scott Mk. III-Fords of Dyson Racing.

The 333 SP’s Italian good looks matched its vibrant sound and there were plenty of buyers for the eventual run of 40 cars. Beyond all this, one of IMSA’s most popular team owner/drivers, Gianpiero Moretti, was a driving force behind the project due to his friendship with Piero Ferrari. Gentleman driver Moretti realized a lifelong dream by winning the Rolex 24 at Daytona on board his MOMO-backed 333 SP in 1998.

Key stat: The 333 SP won all four major endurance races in 1998 – Daytona, Sebring, Watkins Glen and the inaugural Petit Le Mans.

Notable drivers: Max Papis, Gianpiero Moretti, Wayne Taylor.

Nissan GTP ZX-Turbo – 1986-1990 (original IMSA GTP)

Reason for ranking: The Nissan added diversity to Victory Lane in GTP after the early dominance of Porsche and Jaguar – and then won four straight championships.It took several seasons, but in retrospect the combination of racing geniuses behind the Nissan GTP ZX-Turbo were bound to score big.

Electronics engine control maestro Don Devendorf combined with his Electramotive Engineering team co-owner/engine man John Knepp to produce gobs of horsepower that arrived quickly and smoothly. Chassis guru Trevor Harris got the power to the ground. All of this was properly managed by Kas Kastner once he arrived in the front office.

And then there was the genius behind the wheel, Geoff Brabham, who won four straight championships despite in-house competition from Chip Robinson and a slew of never-ending TWR Jaguars. The Achilles heel? The combination was perfect for the 12 hours of Sebring, where it won three times. But the V-6 single turbo was no match for the 24 hours of Daytona.

Key stat: Geoff Brabham won or co-drove to eight straight victories in 1988.

Notable drivers: Geoff Brabham, Chip Robinson, John Morton.

Jaguar XJR-9 – 1988-1989 (original IMSA GTP)

Reason for ranking: The arrival of the Tom Walkinshaw Racing team, initially led by the XJR-9, put the always popular Jaguars in the thick of the hunt at every GTP race until the series’ conclusion in 1993.The Jaguar XJR-9 won its inaugural appearance at the Rolex 24 of Daytona in 1988 and set the tone for a series of XJR racers that followed. The initial 7.0-liter V12 models, including the XJR-12, sounded fabulous and because of the big engines in the back had very distinctive designs.

Like its predecessor two years earlier, the XJR-12 won Daytona and Le Mans in 1990. The XJR-10, powered by a 3.0-liter V6 twin turbo, was used in sprint races and was followed by the bad-ass XJR-16. The succeeding XJR-14 was powered by a 3.5-liter Cosworth and arrived in IMSA after initially being built for the World SportsCar Championship. Despite often winning efforts under team manager Tony Dowe, Jaguar never won a Camel GT championship.

Key stat: TWR ended Porsche’s winning streak at Le Mans in 1988 by tuning up with a victory by its XJR-9 at Daytona.

Notable drivers: Martin Brundle, Jan Lammers, Davy Jones.

Riley & Scott Mk. III – 1995-2002 (IMSA World Sports Cars)

Reason for ranking: The Mk. III customer car was a solid ride for a variety of teams, which helped sustain the WSC category and then helped launch the Grand-Am series.With Dyson Racing’s Ford V8’s in the back, the R&S Mk. III versus Ferrari battles were epic—and a joy to behold thanks to open cockpits. According to the Riley Technology records, the Mk. III had a one-race victory edge in those matchups.

The car’s designer, Bob Riley, is acknowledged as a race car design genius—except in his own mind. Riley says almost every car he ever drew up in an illustrious career always had at least a couple elements he would have done over.

The only car that did not inspire different interpretations from his own mind was the Riley & Scott Mk. III. The car was unique in origin as well since it was the first prototype drawn up using computational fluid dynamics. Front-mounted radiators are often vulnerable and problematic due to heat. But Riley’s Mk. III design proved durable and worthy.

Key stat: 47 career victories.

Notable drivers: James Weaver, Butch Leitzinger, John Paul Jr.

Toyota Eagle MKIII – 1991-1993 (original IMSA GTP)

Reason for ranking: The MKIII dominated the final two seasons of the IMSA GTP.The MKIII was the third time around charm for Dan Gurney’s All American Racers team in its quest to bring Toyota success in the GTP ranks. But because of a relative lack of cars as the GTP era wound to a close, the MKIII’s ranking gets dinged a bit.

The car’s four-cylinder turbo was severely challenged by an air restrictor, which team owner Gurney likened to the size of “a hummingbird’s asshole.” But the little 2.1-liter engine produced 800 hp. The MKIII dominated the final two years of GTP, generating 10,000 pounds of downforce at the top speed of 200 mph. The car was known inhouse as the “WFO.” Officially, that was for designer John Ward, aerodynamicist Hiro Fujimora and Others.

Key stat: the MKIII won 21 of 27 races, including the 1993 Rolex 24 at Daytona. At one point, the Gurney team won 14 straight races.

Notable drivers: Juan Manuel Fangio II, P.J. Jones, Rocky Moran.

Porsche RS Spyder LMP2 – 2005-2010 (IMSA/ALMS LMP2)

Reason for ranking: One of the few cars that could keep Audi’s factory teams out of Victory Lane.

The RS Spyder was certain to be a winner because Team Penske helped design it along with Porsche engineers and then ran it as an LMP2 entrant.

Later, Dyson Racing entered in LMP2 as well. This often insured a class victory. But due to lighter weight than the Audis, good fuel mileage and efficient pit stops, the RS Spyder LMP2 regularly contested for the overall victory.

Key stat: The Porsche Spyder of Penske beat Audi and Acura to win the Sebring 12 hours overall in 2008.

Notable drivers: Sascha Maassen, Lucas Luhr, Romain Dumas.

Kudzu DLM – 1996-1998 (World Sports Cars; Le Mans LMP-2)

Reason for ranking: Constructed by Jim Downing, the DLM was the only American-built prototype driven to a class victory at Le Mans by its builder. This Kudzu chassis ran regularly in IMSA, but was best known for its exploit at Le Mans, where it scored an LMP2 class victory in 1996.

No American-built prototype has won at Le Mans since. Jim Downing, whose Downing/Atlanta shops built the Kudzus, Franck Freon and Yojiro Terada did the driving. Powered by three-rotor Mazdas built by the late Rick Engman, the Kudzu scored a podium at Daytona prior to being shipped to Le Mans. The car later appeared with a four-rotor Mazda and was known as the DLM-4.

Key stat: Competed in 34 IMSA races in addition to Le Mans.

Notable drivers: Jim Downing, Tim McAdam, Rich Grupp.