The No.1 Audi took an astonishing victory in the Petit Le Mans despite Allan McNish having crashed the car on the way to the grid.
Peugeot had to settle for second place again, after leading most of the event.
The lead Audi R10 TDi suffered heavy damage at both ends when McNish lost control on cold tyres during a reconnaissance lap just under an hour before the start, and despite heroic efforts the Champion team were not quite able to fix the car in time for the green flag.
McNish, who shared the No.1 Audi with Dindo Capello and Emanuele Pirro, went into the race already two laps down, yet a charging drive and wise strategy saw the car back on the lead lap within three hours.
For most of the race the battle up front was between the No.2 Audi and the sole Peugeot 908 HDi FAP, with the two cars repeatedly exchanging the lead, including some spectacular passes in traffic. They were rarely more than a few seconds apart in the first nine hours of the race, although the Peugeot always seemed to have a slight speed advantage.
The No.1 Audi took a while to join the lead fight once back on the lead lap, having lost a little more time with a puncture.
But at the penultimate restart with 35 laps remaining, McNish completed his epic charge by sprinting from fourth place to first within a handful of laps, swiftly passing the No.5 Penske Porsche, his teammate Marco Werner, and finally Peugeot's Christian Klien to move into the lead.
Klien tried to fight back but his efforts were vigorously rebuffed, and when McNish made a clear break at the final restart he was able to ease away and clinch Audi's ninth consecutive Petit Le Mans victory.
Second was definitely not the result Peugeot trio Klien, Nicolas Minassian and Stephane Sarrazin wanted, while Werner and Lucas Luhr claimed third overall for the second Audi.
The LMP2 battle saw a spectacular result for Porsche and an abject disaster for Acura, as Penske Porsche's Romain Dumas and Timo Bernhard clinched the class title on a day when Porsche took a one-two-three-four sweep in class, and all four Acuras crashed.
Although divergent pit strategies often elevated LMP2 cars into the overall lead, the less powerful prototypes didn't have the speed to fight with the LMP1 diesels at Road Atlanta and were always swiftly shuffled back.
Ultimately it was Penske's visiting IndyCar duo Ryan Briscoe and Helio Castroneves who emerged victorious in the class contest, as their teammates Dumas and Bernhard focused on wrapping up the title in second place.
Sascha Maassen, Patrick Long and Emmanuel Collard took third, with Penske filling the top three in both qualifying and the race, ahead of Marino Franchitti, Butch Leitzinger and Andy Lally's Dyson Porsche.
Acura's biggest disaster was the crash that ended Highcroft duo Scott Sharp and David Brabham's LMP2 title hopes, as Sharp went off at Turn 10B just 16 laps into the race and sustained too much damage to continue. The team had only just built up a brand new car after Sharp's massive Thursday accident, and with the two shunts ruling Highcroft out of most of practice and the majority of the race, guest driver Dario Franchitti never had the chance to drive the car in an official session.
Andretti Green Racing proved to be Acura's best hope for victory in the race, only for the No.26 car to be eliminated in a frightening late crash while still in contention for the class win.
The incident was caused when George Forgeois spun his Intersport Lola and stalled while preparing for a restart. The unsighted Patrick Pilet (Flying Lizard Porsche) slammed into the Lola, destroying both cars and scattering debris across the track. AGR's Franck Montagny collected a stray wheel, breaking his suspension and sending him into an accident of his own. All three drivers were thankfully unhurt.
The de Ferran car was the highest finishing Acura in fifth in class, but was delayed early on when Gil de Ferran went off the road and lost several laps. Fernandez Racing also fell victim to an accident, the car crashing out in Luis Diaz's hands.
The LMP2 result remains provisional, however, as Highcroft entered a pre-race protest against all five Porsche RS Spyders, alleging that they were using illegal fuel.
Two of the new prototype entrants showed great promise, with the LNT Ginetta Zytek briefly leading thanks to an alternate pit strategy. Inconveniently timed yellows saw Danny Watts and Olivier Pla fall a lap down soon afterwards though, and a later brush with the Farnbacher Loles GT2 Porsche and several resultant penalties put them out of contention.
The Corsa Zytek demonstrated impressive fuel mileage and ran as high as fourth, but then crashed out spectacularly at the final corner two hours into the race, with Stefan Johansson ending up balanced atop the tyre wall after an apparent mechanical problem at the front of the car. The Swede escaped injury.
The GT2 drivers' title was also settled thanks to Jorg Bergmeister and Wolf Henzler's second place for Flying Lizard Porsche, co-driving with Marc Lieb on this occasion.
Risi Ferrari's Jaime Melo and Mika Salo recovered from an early delay due to an obstruction in the throttle system to win the class, with the Tafel Ferrari taking third, while Farnbacher Loles Porsche's hopes were ruined by the tangle with the LNT Zytek.
A trouble-free run for Johnny O'Connell, Jan Magnussen and Ron Fellows saw them win GT1 by six laps over Corvette teammates Olivier Beretta, Oliver Gavin and Max Papis.