FIA says 2026 F1 compression ratios measured at ambient, prompting consternation

The FIA has confirmed that compression ratios for Formula 1’s 2026 engines are measured under static, ambient conditions, a clarification that has prompted consternation among teams. Under the 2014–2025 rules the ratio was 18:1, but for 2026 it has been reduced to 16:1. The measurement is taken at ambient temperature, not while an engine is running; a running engine is much hotter and metals expand.

Because the engines have very short throws, small thermal expansion can reduce the distance between piston and cylinder head at top dead center and raise the effective compression ratio, a change that could yield as much as 15 hp (11 kW) or a few tenths of a second per lap. The FIA said, "This procedure has remained unchanged despite the reduction in the permitted ratio for the 2026 season.

It is true that thermal expansion can influence dimensions, but the current rules do not provide for measurements to be carried out at elevated temperatures." The article says, "So if Mercedes and Red Bull do have a horsepower advantage, it’s one that will likely be baked into the 2026 season." The FIA also clarified rules around ultrasonic fuel-flow meters.

Under the outgoing regulations flow was capped at 100 kg/h; with a move to fully sustainable synthetic fuels the limit becomes an energy cap of 3,000 MJ/h.

Key Topics

Sports, Fia, Mercedes, Red Bull, Compression Ratio, Fuel Flow Meter