This IMSA GTO homage brings back the flamethrower

By Johan Dillen
Dec 3, 2023 | Audi, IMSA, IMSA GTO, Audi 90 | Posted in Features | From the Aug. 2018 issue | Never miss an article

Photography by Dirk de Jager

This is the flame-spitting silhouette that sent shivers down the spines of those on IMSA grids during the 1989 season. It was designed to erase the image problems Audi had been experiencing in the U.S. for the past couple of years, and in that respect it succeeded. 

The team didn’t win the championship that year–they missed the first two races of the season–but the program made a lasting impression: You don’t mess with Audi. 

In an age when motorsport is becoming ever more silent, our visit with this nearly perfect recreation of Audi’s GTO machine reminds us of how racing was back then: loud, spectacular and with accompanying fireworks. What good is having 700 horsepower if you can’t clearly convey that fact to the audience?

This machine recalls a thrilling chapter in Audi Sport’s long history, since the genuine article formed the link between Audi’s triumph in the World Rally Championship and its successes in circuit racing. Both venues showcased four-wheel drive and a small yet heavily turbocharged engine.

The man behind this recreation was also an instrumental part of Audi Sport’s history. Karl Hasenbichler worked on Audi’s racing engines from the rally days all the way through the LeMans period. 

I started in 1983 and retired in 2015,” the Austrian-born engineer said. “But retirement is not really my style, so I try to keep busy. Since I have been around for most of Audi’s racing and rallying history, people tend to find me. I have just finished restoring an original V8 DTM car, for example.”

Racing Pedigree

Hasenbichler was not just an engineer; he was also a more than decent racing driver in his day. The chassis used for this recreation actually raced in South Africa, Germany and Belgium, sometimes with Hasenbichler himself behind the wheel. 

“This car was originally an Audi 80 Competition that Finnish driver Pertti Kuismanen bought to race in the ’90s,” Hasenbichler explained. Kuismanen also owned an Audi S4 GTO, which was basically an IMSA-spec car built after Audi Sport dropped that program. 

Kuismanen drove that S4 GTO to 1996 and 1997 German touring car championships. Then series organizers outlawed the car.

“I took care of his engine at the time, and we started wondering what the next step might be,” Hasenbichler continued. “So we decided to do something spectacular.” They completely stripped the 1994 Audi 80 Competition shell and filled it with the IMSA-spec drivetrain from the S4 GTO.

At the time, the Belgian championship welcomed both GT and touring cars. “It had a fairly liberal set of rules, so we were able to enter the car,” Hasenbichler noted. “It was an endurance championship, so Pertti asked me to join him for driver duties. I have always raced, but on a minimal budget–I did quite well in the Interseries, for instance. It was my choice to do it this way: I enjoyed racing on a small budget for fun, and then going back to the ever bigger works operation for a living.”

Hasenbichler also had more experience than most others: “I am the only guy who drove all the racing Audis. If something needed to be tested like ‘right now,’ I was often the one behind the wheel.”

The duo was quite successful with the car, winning the 2001 overall championship. “And we won a six-hour race at Spa outright amongst a field of Vipers and Porsche 996 bi-turbos,” Hasenbichler added. “It started to rain during the race, but I opted to stay out on slicks. Everybody was struggling and came back to the pits for rain tires. I could cope with the conditions thanks to our four-wheel-drive system. It has worked wonders for Audi all through our history.”

“I Just Love My Audis”

Soon after a third-place finish at the Nürburgring, in 2002 Kuismanen retired the Audi 80. He switched to a Viper.

A few years later, German Audi enthusiast Rainer Bonetsmüller was able to buy Kuismanen’s S4 GTO and Audi 80 Competition. “I just love my Audis,” the German explained with the biggest of grins. 

“The IMSA history has so much going for itself,” Bonetsmüller observed. “I just wanted to have a part of it. We see so little of it nowadays. Audi has the original No. 4 car in its museum, but only takes it out for occasional displays and limited runs. According to them, the car has become difficult to operate.”

So Bonetsmüller had an idea: Why not create a replica of the original GTO car? “We asked if they would object to this recreation, and they wholeheartedly supported our idea,” he reported.

Rainer Bonetsmüller, above, believed that one of the most evocative Audis ever built should be spitting fire, not confined to life in a museum. He couldn’t buy one of the famed IMSA racers, so he built his own with help from Karl Hasenbichler, long associated with Audi’s factory motorsports programs.

This would be a tribute, though, not a race car. Although Bonetsmüller enjoyed a fairly substantial racing career himself, with outings in the FIA GT championship among them, his racing days are over. “I only drive for my enjoyment nowadays,” he said. “I don’t want to take too many risks anymore.” He’s simply after some fun with his cars.

The GTO tribute car would be based on the Audi 80, since it already had the IMSA-spec engine. “The roof of the Audi 80 is identical to that of the Audi 90 that we used for the real IMSA car,” Hasenbichler explained. “The rest is tubular-frame technology, as it was in the day.”

Like the original, this car’s flares are formed in Kevlar. The graphics are also spot-on. Unlike the original, though, this one won’t be parked in a museum. After running its shakedown laps at Autodrom Most in the Czech Republic, Bonetsmüller hopes to put the car on tour. 

Hasenbichler set out to build an almost identical copy. “I went out and found the original plans for the body panels in the U.S.,” he reported. “We decided to make them out of Kevlar, as we used them in the ’90s. Kevlar is actually lighter than carbon and less prone to breaking. Front and rear are made of aluminum tubing. It now has a six-speed manual gearbox, exactly as it was used in IMSA including a working rearwards gear as specified by the regulations.”

This Time, No Restrictor

That six-speed receives a lot of power. “Because there is no need for a restrictor anymore,” Hasenbichler explained, “we are able to run the engine up to 3.3 bar of turbo pressure. It puts out 800 horsepower, which is more than it did at the time.”

Only a few small clues separate the recreation from the one that Hans-Joachim Stuck and Walter Röhrl drove in IMSA competition. The tail lights, for example, come from an Audi 80; on the genuine article, they’re from an Audi 90. Also, the tribute car’s side exhaust dumps its flames closer to the rear wheels. “But everything else is just as it was at the time it raced,” Hasenbichler said.

The day we visited, this touring car icon was ready for its maiden voyage, which was not trouble-free. After a first effort to produce that five-cylinder bark was aborted, the original Bosch diagnostic equipment was summoned for help. The problem was quickly traced and sorted. The next time, the whine of the starter was followed by the irregular off-beat of a five-cylinder engine.

One important factor sets Bonetsmüller’s replica apart from its inspiration: It’s not restricted by racing regulations. Thanks to nearly 50 psi of boost, its turbocharged engine makes about 800 horsepower. Aside from a few other small differences, this car is 1989 all over again.

Climbing aboard requires some gymnastics, since the doors don’t open. Bonetsmüller had to wriggle his body through the window opening, but his smile once inside said that the gymnastics were worth it. 

Flamin’ Heck

Bonetsmüller gently let the car roll out of the pit box and pointed it to the straight. After a few easy laps, he picked up the pace. The turbo whine complemented the raw bark of the five cylinders. 

As the speed increased, the picture became more impressive as each lap passed–and then came the flames that accompanied the downshifts. 

“Did you see the flames?” Bonetsmüller laughed as soon as he had stopped and removed his helmet. Then he just sat there, taking in his recreation. 

The attention to detail in this car is just superb. All the decorations are painted on, with two subtle differences separating this one from the original: Here there isn’t a mention of Stuck or Röhrl; instead, the names on the roof are those of Rainer and his wife, Anita. The second change: A sticker on the rear window states “Race for Anita.”

Bonetsmüller has recreated a piece of history. It recalls a time when Audi entered a new venue with an unorthodox recipe.

What’s next for the car? Bonetsmüller hopes to receive calls from event organizers. He’ll be happy to shoot some flames for them, too. 

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AnthonyGS (Forum Supporter)
AnthonyGS (Forum Supporter) UltraDork
6/30/22 12:32 p.m.

I love it!  This is inspiring for my new project.

Noddaz GRM+ Memberand UberDork
6/30/22 12:57 p.m.

I want that paint job on an Audi for the street!

iansane GRM+ Memberand Dork
6/30/22 2:09 p.m.

When I bought a '90 90 a few years ago the first thing I did was try to find a halfway economical way to mimic that IMSA car. So ridiculously cool.

trumant GRM+ Memberand Reader
6/30/22 7:12 p.m.

Video, sound? I desperately need to see this thing in motion and here it's ridiculous turbo noises!

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