Engine Compression Ratio Rules Modified: All Five Manufacturers Aligned on FIA Update
The FIA has announced a regulatory adjustment to engine compression ratios that will take effect on June 1st. All five engine manufacturers operating in the sport have formally agreed to the modification.
In a significant regulatory development, the FIA has secured unanimous approval from the sport's five engine manufacturers regarding modifications to compression ratio specifications. The new regulations are set to come into force on 1 June.
The agreement represents a coordinated effort among all competing power unit suppliers to implement the technical changes. By securing buy-in from every manufacturer involved in the championship, the FIA has ensured a smooth transition to the updated engine regulations without competitive disadvantage or protest.
The compression ratio adjustment marks another evolution in Formula 1's technical rulebook, reflecting the sport's ongoing commitment to balancing performance, reliability, and standardized competition parameters across the grid.
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Related Regulations
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Full Regulation Text
Article C5.4.3
Geometric compression ratio limit
Chapter: C5
In Simple Terms
F1 engines have a limit on how much they can compress the air-fuel mixture inside each cylinder. No cylinder is allowed to have a compression ratio higher than 16.0, which means the mixture can be squeezed to no more than 16 times its original volume. Manufacturers measure this themselves following FIA guidelines.
- Maximum compression ratio of 16.0 applies to every cylinder in the engine
- Compression ratio measures how much the air-fuel mixture is squeezed before ignition
- Each engine manufacturer is responsible for measuring and verifying their own compression ratio
- Measurements must follow FIA-provided guidance to ensure standardization
Official FIA Text
No cylinder of the engine may have a geometric compression ratio higher than 16.0. The procedure to measure this value will be detailed by each PU Manufacturer according to FIA guidance.
Article 1.1
Homologation dossier submission
Chapter: Appendix C5
In Simple Terms
Before a new engine manufacturer can supply power units to F1 teams, they must submit official documentation to the FIA by March 1st of their first year competing. Each manufacturer can only submit one set of these documents.
- Engine manufacturers must register with the FIA before competing
- Homologation dossier (technical documentation) must be submitted by March 1st of the first year supplying engines
- Only one homologation dossier is allowed per manufacturer
- This ensures all engines meet F1 technical regulations and standards
Official FIA Text
Any PU Manufacturer registered must submit to FIA a Power Unit homologation dossier before 1 March of first year intending to supply. Each PU Manufacturer shall present only one homologation dossier.
Article 2
Information provided by the PU Manufacturer to their customer F1 Teams
Chapter: APPENDIX C5: HOMOLOGATION AND DEVELOPMENT OF POWER UNITS, FUEL AND OIL FOR 2026-2030
In Simple Terms
Engine manufacturers must give F1 teams detailed plans and specifications of their power units in two stages: a preliminary version by August and a final version by November of the year before competition. If anything significant changes after August, the manufacturer must notify teams immediately, and if teams think the changes are unfair, they can ask the FIA to investigate within 7 days.
- Engine manufacturers must provide preliminary technical specifications and 3D models to teams by August 1st of the year before competition
- Final detailed specifications, operating parameters, and installation procedures must be submitted by November 1st
- Any significant changes after August 1st require immediate notification to customer teams and FIA approval
- Customer teams have 7 days to challenge unreasonable changes, with the FIA deciding within 14 days whether modifications are acceptable
Official FIA Text
Any PU Manufacturer intending to supply a Power Unit to an F1 Team during a Championship (year N) must: a. Declare to the FIA, before 1 August of year N-1, that they provided to their customer F1 Teams: i. An initial full external space model of the Power Unit including details and locations of all physical interfaces required by the team to install the Power Unit. ii. Preliminary estimates of important operating parameters such as heat rejection, fuel mass and density, clutch shaft stiffness and engine stiffness. b. Declare to the FIA, before 1 November of year N-1, that they provided to their customer F1 Teams: i. A final full external space model of the Power Unit including details and locations of all physical interfaces required by the team to install the Power Unit. ii. Firm predictions of important operating parameters such as heat rejection, fuel mass and density, clutch shaft stiffness and engine stiffness. iii. Initial details of any other parts, procedures, operating conditions and limits or any other information required by the team to install and operate the Power Unit as intended. After the 1 August of year N-1, any significant change compared to previous communication, must be notified to the customer F1 Teams in due time. Should a Customer Team consider that the change has an unreasonable impact on the Power Unit installation in the car, they may contact the FIA within 7 days of the notification. The FIA will then contact the relevant PU Manufacturer and its customer F1 Teams in order to conduct its investigation. If the FIA is satisfied, in its absolute discretion, that these changes are acceptable, the FIA will confirm to the PU Manufacturer and the customer F1 Teams within 14 days that they may be carried out.
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