Autobayng News Team
The FIA has confirmed Formula 1’s hotly-disputed rules on engine compression ratios will undergo two changes over the coming 12 months.
The first change will take place this year and earlier than the governing body indicated at the beginning of February. The planned change at the summer break will instead come into force from June 1st, between round seven in Canada and round eight in Monaco.
The change will address how teams’ compliance with the maximum cylinder compression ratio of 16:1 is tested. It follows speculation Mercedes’ engines exceed the limit while running at operating temperatures.
At present, compression ratios are only checked while the engines are cold. From round eight of this year, a second check of the ratios will be conducted at operating temperatures of around 130C.
From the 2027 season, the FIA will cease performing the cold temperature test and only the higher temperature check will apply.
The FIA confirmed the new rules have been confirmed with the unanimous approval of the World Motor Sport Council. “Some aspects of the amendments were concurrently approved unanimously by the Formula 1 power unit manufacturers,” it added in a statement.
“A significant effort has been invested in finding a solution to the topic of the compression ratio. This parameter, which was one of the key fundamental targets of these regulations in order to attract newcomers to the sport, is limited in the regulations to 16:1, measured in cold conditions.
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“The FIA has worked to find a compromise solution which determines that the compression ratio will be controlled in both hot and cold conditions from 1 June 2026, and subsequently only in the operating conditions (130C) from 2027 onwards.”
The relevant article of the 2026 technical regulations, C5.4.3, has been modified. It now states: “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 31st May 2026: when the engine is at ambient temperature; From 1st June 2026 to 31st December 2026: when the engine is at ambient temperature as well as when the engine is at 130C. 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.”
Each power unit manufacturer will define the method by which its engine is checked, which must be approved by the FIA’s technical department.
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