Mercedes compression ratio under review: PUAC to vote on new measurement system from August
The debate over Mercedes’ Formula 1 engine compression ratios is set to take a decisive turn next week, as the sport’s governing bodies and engine manufacturers prepare for a crucial vote.
The decision
The FIA and FOM were expected to release a formal statement today regarding allegations that Mercedes engines may exceed the 16:1 compression ratio limit during operation. In an official communication, the Federation confirmed that an agreement has been reached to conduct a vote within the next ten days.
The focus of the controversy centers on the introduction of a new measurement system capable of evaluating the compression ratio under operating temperatures, not just at ambient conditions, as current regulations specify. This change could significantly impact how engine compliance is verified going forward.
The vote and potential implementation
The Power Unit Advisory Committee (PUAC) will hold an electronic vote to decide on the adoption of the new hot measurement system, which would operate at a representative temperature of 130°C, starting from August 1, after the Formula 1 summer break.
PUAC members include major power unit stakeholders Audi, Ferrari, Honda, Red Bull Powertrains, and Mercedes, alongside the FIA and FOM. Approval requires six out of seven votes. Assuming Mercedes opposes the change, the FIA and FOM will effectively hold the deciding influence. The very existence of this proposal signals a regulatory willingness to pursue modifications to the current system.
Once the PUAC completes its ten-day voting period, the final authorization will rest, as always, with the FIA World Motorsport Council, determining whether the updated hot measurement method will be officially implemented.
The outcome of this vote could therefore have massive implications for the 2026 hierarchy. If the new measurement standard is adopted, Mercedes and its customer teams may be forced to quickly adapt their cylinder head designs during the summer shutdown, potentially losing a key performance advantage they have allegedly enjoyed during the early phase of development. With rival manufacturers pushing for maximum transparency, the next ten days will determine whether the technical regulations will be tightened to close what many consider a legal loophole in the pursuit of 2026 supremacy.
