The FIA has introduced a revised power unit compression measurement process ahead of the F1 2026 season beginning.<\/p>\n
A revised version of the Technical Regulations details an expedited change that will see a \u2018hot\u2019 measurement taken from June 1.<\/p>\n
FIA confirms hot and cold compression ratio checks for 2026<\/p>\n
Want more PlanetF1.com coverage? Add us as a preferred source on Google<\/a> for news you can trust.<\/p>\n Claims that a grey area in the wording of the compression ratio regulations send the F1 paddock into a spin during the off-season.<\/p>\n Allegations centred on Mercedes, with claims it had found a way to meet the measurement requirements while running at a higher compression ratio on track.<\/p>\n While never denied in as many words, it was also never conclusively proven that Mercedes had designed its power unit in such a way.<\/p>\n Nonetheless, the matter prompted a meeting of the four other power unit manufacturers in Bahrain and an e-vote over a change in the wording of the regulations.<\/p>\n According to a statement released by the FIA, it was proposed that a test be carried out with the engine at 130 degrees Celsius from August 1.<\/p>\n \u201cThe FIA has recently launched an e-vote primarily centred on a proposed change to the assessment of the power unit compression ratio in running condition,\u201d read a statement from the FIA issued to PlanetF1.com last week.<\/p>\n \u201cOver recent weeks and months, the FIA and the Power Unit Manufacturers have collaboratively developed a methodology to quantify how the compression ratio changes from ambient to operating conditions.<\/p>\n \u201cFollowing validation of this approach, a proposal has been submitted whereby, from 1 August 2026, compliance with the compression ratio limit must be demonstrated not only at ambient conditions, but also at a representative operating temperature of 130\u00b0C.<\/p>\n \u201cThe vote has been submitted to the Power Unit Manufacturers, and its outcome is expected within the next 10 days and will be communicated in due course.<\/p>\n \u201cAs with all Formula 1 regulatory changes, any amendment remains subject to final approval by the FIA World Motor Sport Council [WMSC].\u201d<\/p>\n The deadline for that vote was February 28.<\/p>\n However, a revised set of regulations has been published on the FIA website with revisions to Article C5.4.3, which deals with compression ratios.<\/p>\n Much of the original Article has been deleted, with an almost entirely new rule in its place.<\/p>\n It reads:<\/p>\n 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:<\/p>\n \u2013 Until 31 May 2026: when the Engine is at ambient temperature<\/p>\n \u2013 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.<\/p>\n 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.<\/p>\n Under the regulations, power units must be homologated by 1 March.<\/p>\n Following enquiries by PlanetF1.com, the FIA issued a statement to media:<\/p>\n \u201cAmendments to the 2026 FIA Formula 1 Regulations have been approved unanimously by e-vote by the World Motor Sport Council,\u201d the statement began.<\/p>\n \u201cSome aspects of the amendments were concurrently approved unanimously by the Formula One Power Unit Manufacturers.<\/p>\n \u201cThe modifications to the Technical Regulations follow the pre-season tests in Barcelona and Bahrain and extensive feedback received from drivers and teams.<\/p>\n \u201cA significant effort has been invested in finding a solution to the topic of the compression ratio.<\/p>\n \u201cThis 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.<\/p>\n \u201cThe 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.<\/p>\n \u201cThe regulations introduced for 2026 represent one of the biggest changes in recent memory.<\/p>\n \u201cAll parties acknowledge that with the introduction of such significant regulatory changes, there are collective learnings to be taken from pre-season testing and the initial rounds of the 2026 championship.\u201d<\/p>\n More on F1 engines in 2026<\/p>\n Explained: F1\u2019s complex power unit upgrade system<\/a><\/p>\n Explained: How F1\u2019s new \u2018overtaking mode\u2019 will work in 2026<\/a><\/p>\n The development offers an unexpected twist though, theoretically, creates another grey area.<\/p>\n While the revised regulation seemingly closes off the potential for power unit manufacturers to develop engines with compression ratios higher than 16.0, from 2027 it appears to reintroduce the issue.<\/p>\n However, the issue is reversed as, rather than suggestions that a power unit could run above the 16.0 ratio when hot, it\u2019s theoretically possible to run above that ratio from next season when cold.<\/p>\n That exists because, from 2027, there will be no ambient measure, seemingly serving only to move the goalposts.<\/p>\n Meanwhile, in the immediate future, the issue has been sidestepped with no protests expected in Australia \u2013 nor penalties when the revised test is introduced in June, just prior to the Monaco GP.<\/p>\n What happens ahead of F1 2027, however, is a different matter.<\/p>\n Want to be the first to know exclusive information from the F1 paddock? 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