Overview
- The FIA ruled that combustion chambers are legal if compression measures 16:1 at ambient temperature, even if the hot running value is higher.
- Mercedes and Red Bull Powertrains are reported to use thermally expanding chamber designs that can lift effective compression toward roughly 18:1 for an estimated ten-horsepower gain.
- The decision benefits Mercedes and its customers McLaren, Williams and Alpine, with Franco Colapinto set to debut for Alpine, while Red Bull’s units support Red Bull Racing and Racing Bulls.
- Ferrari, Honda and Audi sought clarification on the rule and, according to reporting, face tight timelines to rework V6 designs before 2027, leaving protests or formal remedies as potential responses.
- Under 2026 rules the FIA will audit thermal engine performance every six Grands Prix, granting Additional Development Opportunities above 2% gaps and expanded allowances above 4%, with the first audit slated for Miami.