Toyota’s racing history stretches back nearly 70 years, starting with the company’s rallying start in 1957. Since then, Toyota has built a motorsport dynasty with five Le Mans wins, eight World Rally Championship manufacturers’ titles, 53 IMSA victories and eleven GT500 team wins under the company’s belt. Many of Toyota’s most celebrated racing successes have one thing in common: the 503E inline-four engine.

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Toyota’s 503E engine was born out of Toyota’s desire to dominate all forms of motorsport. During the 1980s, Toyota was taking its motorsport efforts very seriously, especially Le Mans prototype racing and IMSA. Toyota had a 2.1-liter four-cylinder engine known as the 4T-GT in the early years of its Le Mans efforts, but it was underpowered and unreliable. Therefore, Toyota introduced a new 2.1-liter turbocharged twin-cam four-cylinder engine instead.

The new engine was known by many names. Internally, the new engine was called the 503E; however, it was also commonly referred to as the 3S-GT and 3S-G. The 503E received a significant boost and horsepower increase over the 4T-GT, producing between 500 and 850 horsepower in many motorsport applications. Over the next decade, the 503E proved to be a dominant racing engine, powering some of Toyota’s most iconic vehicles to victory in many disciplines of motorsport.

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Toyota entered the 24 Hours of Le Mans for the first time in 1985 with the 85C prototype. This prototype was a collaboration between the TOMs racing team, the Dome chassis manufacturer and Toyota’s TRD Racing Division. The 85C chassis was powered by a turbocharged 2.1-liter Toyota twin-cam four-cylinder engine, known internally as the 4T-GT. Unfortunately, the estimated 500 horsepower 4T-GT was not powerful enough for the 85C to compete with the best in the field, resulting in a 12th place overall finish in the race. Despite returning in 1986 with a completely redesigned chassis, the 4T-GT was once again the downfall of the 86C car that year, as both factory entries were withdrawn from the race due to engine reliability issues.

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For 1987, Toyota was determined to give it a more serious fight. As an evolution of the previous model, the 1987 87C was built on a revised 86C chassis. However, under the skin of the 87C, there was a major upgrade. Toyota decided to replace the lethargic 4T-GT with the race-proven 503E 2.1-liter turbocharged inline-four engine that had already been destroying the competition in the All Japan Sports Prototype Car Endurance Championship. In the 87C, the 503E produced 680 horsepower, 180 more than the old 4T-GT. The 503E-powered 87C won both the Fuji 1000 km and Suzuka that year, but failed to finish the 24 Hours of Le Mans. The 503E was used again in the Toyota 88C in 1988, finishing 12th in the 1988 Le Mans 24 Hours race despite stiff competition.

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IMSA, or the International Motor Sports Association, was founded in 1969 as an American sports car series that offered professional organization on par with NASCAR. By the 1980s, IMSA had become a major player in international motorsports, drawing entries from around the world. In 1983, the All-American Racers team, led by decorated driver Dan Gurney and known for developing Formula One cars in the mid-1960s, teamed up with Toyota to make the IMSA Celica a threat on the racetrack. This effort paid off in 1987 when the AAR-Toyota Celica GTO won the IMSA GTO Manufacturers’ Championship with a 4T-GTE inline-four under the hood.

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After AAR-Toyota’s victory in the GTO category, the logical next step was the more extreme grand touring prototype (or GTP) class. In 1989, to compete in the GTP class, AAR and Toyota entered a new model developed from the Toyota 88C Le Mans prototype car. The new AAR-Toyota HF89 (also known as the Eagle Mk II) featured a rigid aluminum monocoque chassis and a separate rear subframe housing the famous 503E inline-four, producing 630 horsepower in IMSA trim. While the 1989 season was used to fix reliability issues, the HF89 won four races in the 1990 IMSA season and finished second overall.

The next version of the AAR-Toyota GTP car, the Eagle MkIII, was introduced in late 1991 for the 1992 IMSA season. It solved many of the aerodynamic problems encountered by the Eagle Mk II and used a refined version of the 503E, boosted to a full 750 horsepower. What followed was complete dominance, with the Eagle Mk III winning 21 or 27 IMSA races between 1991 and 1993.

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The All Japan Grand Touring Car Championship, known simply as JGTC, was a GT racing series that ran in Japan between 1993 and 2004, later renamed Super GT and continuing to this day. The JGTC consisted of two classes, the lower-spec GT2 class and the fire-breathing, 500 horsepower GT1 class.

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The Nissan R32 GTR dominated every race series it competed in, especially the Japanese Touring Car Championship. The R32 won every Japanese Touring Car Championship race it competed in between 1990 and 1993 (even before the JGTC was formed), totaling 29 wins. This dominance carried over to the JGTC, with the Skyline winning the 1993 and 1994 seasons. Toyota responded by entering the two-year-old Mk IV Supra into the JGTC for the 1995 season. While the 2JZ-GTE was a very special engine in the road car, it was too heavy and inefficient for GT racing. Therefore, Toyota replaced the factory 2JZ-GTE with the 503E, which was tuned from its IMSA counterpart to meet the GT1 spec horsepower limit.

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The Supra lost out to the R32 once again that year and was embarrassed by the dominant McLaren F1 the following year, but 1997 was a watershed year for the 503E-powered Supra. The factory-backed TOMs team battled the SARD team tooth and nail throughout the season and also fielded a 503E Supra, eventually drawing in the final race at Sugo. Due to positive results early in the season, Toyota Team TOMs took the Supra to its first JGTC GT500 victory in 1997. The greatest Supra in racing history went on to win three more championships, largely thanks to the 503E.

(Featured image by Mytho88 via Wikimedia Commons | Cropped and scaled | CC BY 3.0)

The Pikes Peak International Hill Climb is one of the most dangerous and challenging motorsport events in the world. Started in 1916, the PPHC is also the second oldest automotive race in the United States and has attracted the bold and daring manufacturers from the very beginning. While there have been some fast records in the hill climb’s 100+ year history, Rod Millen’s 1994 record behind the wheel of a specially built 503E-powered Toyota Celica is one of the greatest of all time.

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By 1994, racing legend Rod Millen had already competed in IMSA, SCCA PRO Rally, and even the Pikes Peak Hill Climb. However, he wanted his 1994 race to be legendary. Millen decided to partner with Toyota for the 1994 attempt for a few reasons. He thought the new Toyota Celica would be a good platform to start with because its all-wheel drive capabilities would make it good on dirt tracks, and Toyota also agreed to give him some of Dan Gurney’s spare 503E engines from the recently concluded AAP-Toyota IMSA project. Millen set to work adapting the Celica chassis for the hill climb, which used a basic tubular chassis and carbon fiber body. It featured an aggressive aero package and used ground-effect aerodynamics to keep it stuck to the ground. In the hill climb feature, the 503E produced a whopping 850 horsepower.

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In the hill climb, Rod Millen completed the 12.42-mile course in just 10:04.06. With no safety measures to prevent a 5,000-foot tumble down the mountain, Millen negotiated 156 switchbacks and set a new Pikes Peak International Hill Climb record by 40 seconds. Set in a 503E-powered Celica, the record stood for 13 years.