FIA introduces rule change in regulations concerning Mercedes' power unit 'trick'

10:28, 28 Feb

Updated: 10:29, 28 Feb

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byKada Sarkozi

The FIA has published the new rule concerning the measurement of compression ratio of power units.

Ahead of the upcoming Formula 1 season, Mercedes' reported compression ratio 'trick' was a much debated topic in the paddock.

From 1 June, power units will not only be measured at ambient temperature, but also when it is at 130 degrees Celsius, when Mercedes' engine's compression ratio is said to increases from 16:1 to 18:1.

The change was approved unanimously by the World Motor Sport Council, but only some aspects received unanimous approval from the power unit manufacturers.

Photo: Race Pictures

Changes in the regulations

In Issue 16 of the Formula 1 regulations, section C5.4.3, the previous rules are crossed out.

It now reads: "No cylinder, as referred to by C5.1.3, of the Engine may have a geometric compression ratio higher than 16.0, measured in the following conditions:

• Until 31 May 2026: when the Engine is at ambient temperature

• From 1 June 2026 to 31 December 2026: when the Engine is at ambient temperature as well as when the Engine is at 130degC. Any component, assembly, mechanism, or integrated arrangement of components that is designed or functions to increase the compression ratio in operating conditions beyond 16.0 is prohibited."

"The procedure which will be used to assess compliance with this article must be defined by each PU Manufacturer according to the instructions detailed in the document FIA-F1-DOC-042. This procedure must be approved by the FIA Technical Department and included in the PU Manufacturer homologation dossier."

From 2027 onwards, it will be only measured in the operating conditions.