Bourdais, who laid on another clinic in qualifying, drove an exemplary opening stint before van der Zande brought the car home for its second successive win on the challenging 2.35-mile temporary circuit - the Dutchman having paired with Kevin Magnussen last year. But this was no walk in the park.
The Dallara-based Cadillacs were slightly favoured over the more nimble Acuras going into the weekend, despite the Caddys being saddled with an extra 15 kgs of ballast under IMSA’s Balance of Performance regulations.
The top three cars – one Cadillac and two Acuras – were separated by a scant 0.127s in qualifying, while after a breathtaking 73 laps of green-flag racing the top four – three Cadillacs and one Acura – were blanketed by just 1.663s. This was a cracker.
Bourdais looked to have messed up his chances of the pole when he slapped the wall hard at the exit of Turn 8, but incredibly the car sustained no serious damage and he was able to dip fully half a second beneath Juan Pablo Montoya’s track record to secure his fourth pole of the season.
Unlike at Long Beach, where an early mistake caused him to wage a sensational comeback, Bourdais was flawless as he eked out a margin of just over two seconds on Tom Blomqvist’s Meyer Shank Acura by the time they both headed for the pit lane after 36 laps, exactly halfway through the 100-minute race. Alex Lynn, in the second Ganassi Cadillac, was a further 18 seconds adrift when he pitted on the same lap to hand over to Earl Bamber.
Ricky Taylor had stayed with the two leaders before abandoning the Wayne Taylor Racing Acura’s fuel-saving tactics after 28 laps and committing instead to a two-stop strategy for himself and Filipe Albuquerque. Critically, the Action Express Cadillac team had made the same decision much earlier, with team newcomer Olivier Pla (in for Tristan Nunez) completing only 10 laps before being relieved by Pipo Derani.
The Brazilian set a blistering pace and actually led for three laps before making his own final stop at the earliest possible opportunity – with 40 laps in the books and 44 minutes remaining. Derani rejoined in fifth, 34 seconds behind van der Zande, but continued to set an astonishing pace – including a new lap record only 0.059s slower than Bourdais’ pole – as he quickly reduced the deficit. With 20 minutes remaining, the top four were together.
Van der Zande managed his pace perfectly to secure the victory, while Oliver Jarvis (in for Blomqvist) tracked his every move. Mere yards behind, Derani muscled his way past Bamber for third at Turn 1 on lap 60, only for Bamber to repay the favour at Turn 3 with three laps remaining. Sadly, Derani’s hard work came to nought when his car later failed to meet the minimum weight requirement.
Taylor/Albuquerque were promoted to third, but still narrowly ceded the championship points lead to Blomqvist/Jarvis with only four races remaining.
The GTD contest was almost as hard fought with Foyt IndyCar driver Kyle Kirkwood and Ben Barnicoat scoring the VasserSullivan Lexus team’s first victory of the season by 2.2s over the Heart of Racing Aston Martin of Roman De Angelis/Ross Gunn.
De Angelis got the jump on polesitter Kirkwood at the start and pitted one lap before the Lexus - but Kirkwood's strong in-lap in clear air meant Barnicoat emerged ahead of Gunn by three seconds, a lead he maintained to the finish.
Behind, Paul Miller Racing's BMW M4 GT3 completed the podium in third with Madison Snow and Bryan Sellers.
IMSA Detroit race results (73 laps):
| Cla | Class | Num | Driver | Chassis | Time | Gap |
|---|---|---|---|---|---|---|
| 1 | DPi | 01 |
 Renger van der Zande  Sébastien Bourdais | Cadillac DPi | 1:40'45.972 | |
| 2 | DPi | 60 |
 Oliver Jarvis Tom Blomqvist | Acura DPi | 1:40'46.370 | 0.398 |
| 3 | DPi | 02 |
 Earl Bamber Alex Lynn | Cadillac DPi | 1:40'46.755 | 0.783 |
| 4 | DPi | 31 |
Olivier Pla  Pipo Derani | Cadillac DPi | 1:40'47.635 | 1.663 |
| 5 | DPi | 10 |
 Ricky Taylor  Filipe Albuquerque | Acura DPi | 1:41'01.914 | 15.942 |
| 6 | DPi | 5 |
Tristan Vautier Richard Westbrook | Cadillac DPi | 1:41'30.860 | 44.888 |
| 7 | GTD | 17 |
Ben Barnicoat Kyle Kirkwood | Lexus RC F GT3 | 1:40'59.369 | 6 Laps |
| 8 | GTD | 27 |
 Roman De Angelis Ross Gunn | Aston Martin Vantage GT3 | 1:41'01.632 | 6 Laps |
| 9 | GTD | 1 |
Bryan Sellers Madison Snow | BMW M4 GT3 | 1:41'05.181 | 6 Laps |
| 10 | GTD | 12 |
Frankie Montecalvo Aaron Telitz | Lexus RC F GT3 | 1:41'07.517 | 6 Laps |
| 11 | GTD | 32 |
Mike Skeen Stevan McAleer | Mercedes AMG GT3 | 1:41'43.696 | 6 Laps |
| 12 | GTD | 39 |
Robert Megennis Jeff Westphal | Lamborghini Huracan GT3 | 1:41'54.081 | 6 Laps |
| 13 | GTD | 16 |
Ryan Hardwick  Jan Heylen | Porsche 911 GT3 R | 1:42'06.679 | 7 Laps |
| 14 | GTD | 96 |
Robby Foley Bill Auberlen | BMW M4 GT3 | 1:41'39.568 | 8 Laps |
| 15 | GTD | 51 |
Ryan Eversley  Aidan Read | Acura NSX GT3 | 1:34'28.378 | 11 Laps |
| 16 | GTD | 57 |
Russell Ward  Philip Ellis | Mercedes AMG GT3 | 25'59.157 | 56 Laps |
| View full results | ||||||
