Has the boost pressure for the BMW M4 GT3 Evo been radically slashed this year? One might certainly get that impression looking at the 2026 Balance of Performance (BoP) in the DTM or at the Nurburgring 24 Hours race. However, as Motorsport-Total.com has discovered, the car was equipped with a new turbocharger over the winter, which explains the discrepancy compared to previous years. But what prompted this late FIA homologation?
“The introduction was actually planned for 2025,” BMW Motorsport Director Andreas Roos explained in an interview with Motorsport-Total.com. “But because the development time was too long – and also due to the application side of things – we eventually agreed with the FIA and the organizers to delay the introduction until 2026.”
Technically, the new turbocharger made its debut in the M4 GT3 Evo as early as late November 2025 at the GT World Cup in Macau. The Bathurst 12 Hour in February 2026 was still contested using the old turbocharger, as the SRO Motorsports Group, which is responsible for the BoP there, did not conduct its traditional BoP test until after that event.
BMW Motorsport Director: “Main reason was to reduce costs”
“The main reason was to drive costs down, because it is now a 1:1 series-production turbocharger, exactly as it is installed in the M3 or M4,” Roos said, describing the turbocharger swap as a “cost-down measure.” Furthermore, he noted that attention was paid to efficiency and alternative fuels, as their renewable components can sometimes pose a challenge for turbocharged engines. “We tried to make the application more robust in that regard,” he added.
Regarding drivability, Roos does not expect any fundamental shifts. “Perhaps a little bit through the application and the fact that the combustion process has been slightly adjusted,” he said. While this might provide a “slight advantage” in one area, it could also have a “negative” impact in another. Overall, however, he considers the change “negligible.”
In addition to the boost pressure – which is now partly around 0.3 bar lower – another striking change with the new turbocharger is the altered Lambda value, which determines the fuel-to-air ratio in the combustion chamber. Instead of running a Lambda of 1.1, the car is now competing in the DTM with a Lambda of 0.9, which is standard for other turbocharged machinery. This means the fuel mixture is no longer as lean – and the BMW is no longer as fuel-efficient as it once was.
Roos denies connection to Manthey allegations
But what does Roos have to say about the paddock rumors suggesting the change was linked to allegations from competitors that the BMW could occasionally tap into unexpected additional power? “No, that is not true – it has absolutely nothing to do with that,” Roos clarified. “It was our approach, together with the FIA, to change this.”
Apparently, there really is no connection to the allegations made by Manthey last year at the Nurburgring 24 Hours race and the DTM finale at Hockenheim. However, the change is unlikely to have been entirely voluntary.
Did the FIA force BMW into a change?
As Motorsport-Total.com has learned independently from various sources, the FIA reportedly demanded a change to the previous turbocharger. This was apparently because it was not – as required by the regulations and the homologation – a turbocharger that was used 1:1 in the series-production model.
While the previous charger is said to have looked identical from the outside, word is that the internal components were not 100 percent identical to the road-going version. The swap was actually supposed to take place during the racing season last year, but the decision was made to keep it until the end of the season – partly due to the potential impact on the BoP, as the turbocharger is a fundamental part of the vehicle.
But was this irregularity intentional? According to Motorsport-Total.com’s understanding, it is entirely possible that a misunderstanding occurred during the car’s initial homologation and that the FIA, despite its inspection at the time, only became aware of the matter in 2025.
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