F1 rivals seek rule clarity over Mercedes' 2026 engine compression ratio

A technical dispute over Mercedes' 2026 power unit design is escalating, with rivals Audi, Ferrari, and Honda pushing the FIA to clarify measurement rules for engine compression ratios. The controversy centers on whether Mercedes can legally achieve a higher effective ratio during actual running than in static tests, a potential loophole that could offer a significant performance advantage.

Why it matters:

This debate strikes at the heart of Formula 1's new 2026 power unit regulations, designed to level the playing field and attract new manufacturers. If one team is perceived to have found a major performance exploit before the engines are even homologated, it could undermine the competitive balance and spirit of the new rules before the season begins, setting a contentious tone for the new era.

The details:

• The 2026 regulations lowered the maximum compression ratio from 18:1 to 16:1, partly to reduce development costs for newcomers.
• Rivals suspect Mercedes' design complies in a static, cool test but operates at a higher, more efficient ratio at the elevated temperatures of a running engine.
• Audi, Ferrari, and Honda formally requested the FIA to investigate, leading to a series of technical meetings, including a recent Power Unit Advisory Committee session.
• The competing manufacturers are proposing changes to the testing procedure, such as measuring the compression ratio with a pre-warmed engine or using sensors during actual running, to close the potential loophole.
• Any rule change requires a "supermajority" vote, needing approval from four of the five engine manufacturers, plus the FIA and Formula 1 management.

What's next:

Time is critically short, with the 2026 power units set to be homologated on March 1st.

• Red Bull Ford Powertrains holds a key swing vote. Reports suggest it may not oppose an intervention, especially if it believes Mercedes would gain a larger advantage.
• The FIA's final stance is awaited; an initial review saw no need for action, but subsequent discussions may change its position.
• Mercedes Team Principal Toto Wolff has vehemently defended his team's position, stating the engine is fully legal and telling rivals to focus on their own projects. The outcome will set a crucial precedent for technical governance under the 2026 regulations.