The FIA confirmed the update following discussions within the sport’s Power Unit Advisory Committee.
Under the 2026 regulations, V6 engines are limited to a 16:1 compression ratio when measured in cold conditions.
The limit was reduced from 18:1 under the previous rule set, introduced in part to attract new entrants including Audi and Cadillac.
Concerns were raised that a cold-only assessment could allow manufacturers to comply at ambient temperature while achieving a higher effective ratio once the engine reached operating temperature. Rivals pushed for the testing procedure to be amended.
From 1 June 2026, the compression ratio will be measured in both cold conditions and at 130°C operating temperature. From 2027 onwards, it will be assessed solely at 130°C.
The change will take effect between the Canadian and Monaco Grands Prix, meaning any technical modifications required to meet the updated test must be completed before the eighth round of the season.
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“A significant effort has been invested in finding a solution to the topic of the compression ratio,” the FIA said.
“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.
“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 (130deg C) from 2027 onwards.”
The governing body also strengthened the wording of the regulations to prevent any workaround designs, stating: “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.”
With the cold test removed from 2027, manufacturers will be evaluated only at operating temperature, altering the design parameters for the next phase of power unit development.
The compression ratio issue has been a central pre-season talking point, with rivals claiming the potential performance gain could be significant and potentially favour Mercedes. Team principal Toto Wolff has insisted the advantage has been exaggerated.
Meanwhile in a separate adjustment, F1 has also revised its qualifying format.
The gap between Q2 and Q3 has been reduced from eight minutes to seven, while Q3 has been extended from 12 minutes to 13.
Further discussions regarding energy management under the new 2026 regulations remain ongoing as teams prepare for the start of the season.
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