With four wins from the first four rounds, Porsche Penske Motorsport had made a perfect start to the IMSA SportsCar Championship 2025 season.
But on Saturday in Detroit, Porsche suffered its first setback of the season, beaten by Cadillac and Acura, with the latter taking its first win of the year.
But as we'll see, it took a manual overhaul of the Balance of Performance and a full course yellow to prevent the factory 963s from making it five in a row.
Why did IMSA change the way It calculates BoP?
Just like in the World Endurance Championship - where Ferrari remains unbeaten so far - the Balance of Performance hasn't delivered the expected results in IMSA.
And just like in the WEC, the process had to be revised in an attempt to curb the overwhelming dominance of one competitor: this time, Porsche Penske Motorsport.
"Changes come following a transparent process that takes in all performance factors," explained IMSA CEO John Doonan before Detroit. "It should enliven the field and potentially increase the variety of winners - not only podium finishers - for subsequent races.
"When the tables come out, you'll see some adjustments in GTP to the Acura and the Cadillac, with both of them gaining power and losing weight. And you'll see it be the opposite when it comes to the Porsche and the BMW."
The Cadillac V-Series.R (-29kg; +11kW below 190km/h) and the Acura ARX-06 (-22kg; +21kW below 190km/h) received a significant boost, while the BMW M Hybrid V8 (+2kg; -27kW) and the Porsche 963 (+11kg; -5kW) were pegged back.
"All of these changes are based on a data-driven process," Doonan added. "We've realised that the rolling process hasn't reacted fast enough to ensure equal and fair competition.
"You want to do the right thing and make adjustments based on a process, but also, when things start diverging in terms of competition - when you've got some cars outside the performance window and some below it - you want to bring everyone back together.
"I think anyone who wants to see exciting racing would support what we're trying to do here, in both GTP and GTD PRO, heading into Detroit."
What impact did this have on laptimes?
From the first free practice session, there was a noticeable resurgence from Cadillac and Acura. That resurgence was confirmed in qualifying, with Acura locking out the front row, pole position going to Nick Yelloly in the #93 ARX-06 with a 1m05.762s. The two BMWs lined up on the second row, and the two factory Porsche 963s were on the third row.
"Fifth place is a pretty solid qualifying result for us in our #6 car, but we can't get to the front with outright speed this weekend, so hopefully we can gain the edge in tomorrow's race with strategy," said Porsche's Matt Campbell after qualifying.
The disappointment came from Cadillac, unable to capitalise on this major BoP shift. Its best-placed car, the #31 Action Express Racing entry, was over a second off pole in seventh. However, it's worth noting that both Wayne Taylor Racing entries had their best times deleted for causing a red flag during free practice.
"I think we did a good lap that was P4, which was only three tenths off pole position," noted Filipe Albuquerque, who qualified eighth. "And because I got traffic in qualifying, I couldn't do a second great lap."
How did Acura and Cadillac manage to beat Porsche?
At the start, Nick Tandy gained two positions to move up to fourth in the #6 Porsche, while Campbell dropped two to seventh. But both Porsche cars delayed their pitstops slightly to benefit from clean air.
As usual, Porsche Penske executed flawlessly in the pits. Felipe Nasr (#7 Porsche) came out in second, just ahead of Renger van der Zande (#93 Acura) and Mathieu Jaminet (#6 Porsche). Once again, Porsche nailed the strategy, especially since the only car ahead was the #10 Cadillac, which delayed its stop even further.
When the Cadillac finally pitted nine minutes later, Ricky Taylor rejoined in second. While Wayne Taylor Racing gained several places with smart pit timing, it wasn’t enough to take the lead. Nasr led for 35 laps and looked set to deliver a fifth straight win for Porsche Penske Motorsport.
But a final full course yellow - nine minutes long and called with 36 minutes to go - wiped out Nasr's four-second lead. Then, with 13 minutes left, he lost three positions in two corners, passed by the #10 Cadillac (with a bold move), the #93 Acura, and the #6 Porsche.
"Thanks to smart strategy and flawless teamwork, we advanced to the front," Nasr said. "Unfortunately, after a caution period about 30 minutes before the flag, we lost pace because we couldn't get the front tyres into the optimal operating window."
Eventually, van der Zande overtook Taylor with four minutes remaining, handing Acura and Meyer Shank Racing their first win of the season.
"I was very strong every time in Turn 1, and he [Taylor] had some traffic," said van der Zande. "I thought, 'If I'm going to have a chance, it's going to be in Turn 1'. I asked the team, and they said, 'Go for it'.
"He had a weaker exit out of the last corner, and just: boom, I went for it. Hey, when you have to go for it, you have to go for it. When I made the pass for the win, I was excited in the car, like a little child."
Cadillac scored its first podium of the season, and its first since reuniting with Wayne Taylor Racing.
"Everything for our race went perfectly for us to go from eighth to first and almost winning," Ricky Taylor said. "I can't say enough about the team and the execution. It's nice to take this solid result into Le Mans."
Top 10 finishers
- Van der Zande / Yelloly (Acura ARX-06 #93)
- R Taylor / Albuquerque (Cadillac V-Series.R #10)
- Jaminet / Campbell (Porsche 963 #6)
- Tandy / Nasr (Porsche 963 #7)
- D Vanthoor / Eng (BMW M Hybrid V8 #24)
- Braun / Blomqvist (Acura ARX-06 #60)
- S. Van der Linde / Wittmann (BMW M Hybrid V8 #25)
- Gunn / De Angelis (Aston Martin Valkyrie #23)
- Delétraz / J Taylor (Cadillac V-Series.R #40)
- Bamber / Aitken (Cadillac V-Series.R #31)
Is the 2025 season wide open again?
Clearly, the answer is no. What would've happened without that final FCY? We'll never know. But even with an unfavourable BoP, Porsche Penske Motorsport once again proved superior, even if Wayne Taylor Racing also played its cards well with the #10.
"After a strong start, we were able to take the lead and control the race for long stretches," summarised Urs Kuratle, Porsche's director of factory Racing LMDh.
"In the end, we couldn't maintain the high pace. Still, we're satisfied with third and fourth place. And let's not forget: this marks 17 consecutive IMSA races since 2023 with at least one Porsche 963 on the podium!"
"It was a good day overall, and we even extended our championship lead slightly," added Jonathan Diuguid, managing director of Porsche Penske Motorsport. "Next week, we head to Le Mans for the crucial test day ahead of the big race."
And yes, Porsche continues to extend its lead in the GTP manufacturers', teams', and drivers' standings. Once again, it can thank BMW M Team RLL, which disappointed again with fifth- and seventh-place finishes, the #25 even receiving two penalties, one after the race.
"What started with a great qualifying and third place unfortunately ended with relatively few points in the race," said Sheldon van der Linde. "We weren't able to capitalise on the good starting position. That's something we absolutely need to improve on."
Ford vs Chevrolet in Detroit
Second in GTP with Cadillac, Chevrolet also had to settle for second in GTD Pro.
Despite a strong showing, the #3 Corvette Z06 GT3.R of Alexander Sims and Antonio Garcia couldn't overcome the #64 Ford Mustang of Mike Rockenfeller and Sebastian Priaulx. Starting from pole, the Mustang led 55 of 81 laps and Rockenfeller claimed his first win since his 2017 Sebring 12 Hours victory with Corvette Racing.
"I had the feeling that I'm in a Ford city," Rockenfeller laughed. "I know there's the GM battle, but we are racing everybody. It's definitely great to have GM behind us. I think you all know that this is a big fight between the two brands, and clearly we are happy."
Sixth place for the AO Racing Porsche 911 GT3 R brought an end to its three-race winning streak across all categories. But the American team and its duo Laurin Heinrich and Klaus Bachler retain the lead in the GTD Pro team and driver championships.
