The German manufacturer isn’t achieving its 18:1 compression ratio through metal expansion alone. According to Auto Motor und Sport, the Brixworth-designed six-cylinder engine features a second combustion micro-chamber that is deactivated when hot. The FIA has already certified the solution as legal, but what will happen next to avoid the looming threat of formal protests?
As the days pass, the engine controversy continues to swell. At the W17 presentation earlier this week, Toto Wolff resolutely repeated that the Mercedes-AMG F1 M17 E Performance power unit is perfectly legal and that the competition simply needs to “get their act together.”
The FIA has given the green light to the solution that allows the Brixworth V6 to reach a compression ratio of 18:1 when the engine is running hot, while still respecting the 16:1 limit when verified by technical delegates led by Jo Bauer at ambient temperature.
Mercedes feels bulletproof thanks to the documentation they hold from the International Federation (the PU head on Nikolas Tombazis’ staff is Frenchman Vincent Pereme, a former Ferrari engineer with a past at Peugeot). Rumors suggest that the Chairman of the Board of Management of Mercedes-Benz Group AG, Ola Källenius, would be willing to go to court if the regulations were to be revised retroactively.
According to previews from the German outlet Auto Motor und Sport, the battle isn’t being fought over material expansion to lower the head and increase compression. Instead, the Mercedes engine reportedly features a second micro-combustion chamber in each cylinder. When cold, this ensures the volume required to meet the 16:1 ratio defined by the new regulations; however, during “hot” operation, it is excluded by exploiting the extremely high pressures generated by the German unit.
On a theoretical level, this advantage has been calculated at around ten horsepower, which could be worth a couple of tenths per lap. But the Silver Arrows’ advantage may go further: the new sustainable fuel may have been designed with molecules capable of reaching peak efficiency at an 18:1 ratio, amplifying the performance gain by another couple of tenths. This is thanks to a fuel with a higher calorific value that could also provide a weight-saving benefit.
It is no coincidence, then, that much has been written this winter regarding Mercedes’ indisputable superiority. While the FIA has granted a “license of legality” to the controversial solution, other manufacturers are ready to revolt, threatening to lodge official protests at the season opener in Australia.
It is easy to imagine the mood of Stefano Domenicali, CEO and President of Formula 1, who risks being caught in the crossfire just as the era of “agile cars” is beginning. Honda, Ferrari, Audi, and apparently even RBPT (it’s said Milton Keynes learned of the Mercedes “trick” a while ago but lacked the time to implement it in their own engine) are not manufacturers willing to play secondary roles.
A meeting of the PUAC (Power Unit Advisory Committee) is scheduled for today, but it is unlikely that solutions requiring a unanimous vote will be found. Since the FIA cannot easily disavow its own decisions, loopholes must be found to prevent a full-frontal engine war that would be detrimental to the sport’s ecosystem.
At the very least, manufacturers want to invoke the ADUO (Additional Development and Upgrade Opportunities), a regulatory appendix that allows for the development of internal combustion engines with financial support. This would prevent those needing to catch up from exceeding the cost cap if, by the sixth race on the calendar (Miami), the FIA measures a power disparity of 2% compared to the top-performing unit.
It is clear that all engine manufacturers are ready to start designing a second micro-chamber in the cylinder head to align with Mercedes, but how long will it take? Some believe not before 2027; others want to fast-track the process by skipping traditional casting or machining, utilizing additive manufacturing (3D printing). This production process allows for the creation of complex 3D objects from digital models much faster, potentially as early as mid-summer.
And in the meantime? Perhaps a compromise could be sought to immediately reduce the calorific value of Mercedes’ fuel. This year, the FIA flow meter does not measure fuel flow rate, but energy. Each e-fuel will be assigned a certain calorific value based on the sample each supplier homologates, and we will undoubtedly see significant performance swings in this area as well. What will happen? We will find out soon enough…
The technical ingenuity displayed by Mercedes has effectively moved the first battle of 2026 from the asphalt of Sakhir to the drawing boards and FIA committee rooms. As rivals scramble to implement 3D-printed solutions to close the gap, the start of this new era may be defined not by who built the best car, but by who successfully navigated the finest print of the engine regulations.
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