The FIA is reportedly preparing a significant change to Formula 1’s engine regulations for 2027, introducing a sensor to measure compression ratios in real time and potentially bringing an end to Mercedes’ controversial dual combustion chamber solution. The proposed change would also affect a similar concept developed by Red Bull Powertrains, following months of debate over how manufacturers have interpreted the 2026 power unit regulations.
Although the agreement has attracted relatively little attention and has yet to be officially announced, it appears that a solution has been reached for next season. The FIA wants to prevent increasingly extreme technical interpretations from forcing rival manufacturers into an expensive development race, with the new measurement system intended to establish clearer limits.
Mercedes dual combustion chamber solution set to disappear under 2027 F1 rules
The controversy surrounding the Mercedes power unit dominated discussions throughout the winter, generating considerable disagreement among manufacturers and technical observers. Although the debate gradually faded, the underlying issue was never entirely forgotten.
Under the reported agreement, the Mercedes engine will no longer feature its dual combustion chamber in 2027. A comparable solution incorporated into the cylinder head of the Red Bull Powertrains V6 is also expected to disappear.
The central issue concerns the methods used to verify engine compression ratios. During 2026, the FIA introduced checks intended to assess the engines under hot conditions, with the oil brought to 130°C. However, the practical difficulties associated with those inspections created complications for the governing body’s technical officials.
Without diagnostic equipment capable of carrying out the necessary measurements safely at those temperatures, inspectors had to wait for the cylinder head being examined to cool down before proceeding.
It is therefore perhaps unsurprising that the inspections did not reveal abnormal values, particularly as a tolerance allowing a compression ratio of 16.7:1 had also been approved.
FIA plans real-time compression ratio sensor for 2027 Formula 1 engines
From 2027, the proposed introduction of a sensor inside the combustion chamber would allow the FIA to monitor the compression ratio in real time, rather than relying on the complicated inspection procedures used previously.
The compression ratio is the mathematical relationship between the maximum and minimum volumes inside an internal combustion engine’s cylinder. It indicates how much the air-fuel mixture is compressed before combustion takes place.
Under the 2026 Formula 1 technical regulations, the permitted compression ratio is 16:1, compared with the 18:1 figure reached by engines under the previous rules.
Mercedes developed a solution that complied with the regulatory limit when the engine was cold but could reportedly return to the previous compression conditions when operating at higher temperatures, providing a competitive advantage.
The crucial detail was that the technical regulations specified that compliance checks were to be conducted at ambient temperature. Mercedes therefore devised an approach that satisfied the prescribed measurement conditions while behaving differently once the engine reached its normal operating temperature.
Why the Mercedes F1 engine solution divided opinion
The Mercedes concept sparked sharply contrasting reactions within Formula 1. Some regarded the engineering solution as ingenious, while others considered it an illegal interpretation that should have been banned.
Despite considerable hesitation, the FIA’s position was ultimately that the dual combustion chamber complied with the regulations.
The issue, however, extended beyond the legality of a single manufacturer’s design. Allowing such solutions to continue could encourage rival power unit suppliers to invest heavily in developing similar systems, creating an expensive technical arms race.
That prospect appears to have influenced the decision to revise the verification procedure for 2027. Rather than requiring manufacturers to pursue increasingly complex interpretations of the compression ratio rules, the FIA intends to introduce a different monitoring system.
Mercedes and Red Bull face changes as FIA seeks to limit F1 development costs
The introduction of an in-cylinder sensor is expected to eliminate the Mercedes dual combustion chamber solution, together with the comparable design used by Red Bull Powertrains.
The change is also expected to coincide with the disappearance of Ferrari’s blown exhaust concept, as the governing body seeks to restrict particularly extreme interpretations of the technical regulations.
The FIA’s broader objective is to limit the escalation of development costs and performance gains associated with increasingly sophisticated engineering solutions.
For Mercedes and Red Bull Powertrains, the reported agreement would mean revisiting concepts developed around the 2026 regulatory framework. For the wider championship, it could establish a more direct method of monitoring compliance while reducing the incentive to pursue costly alternatives.
Nevertheless, Formula 1 teams have consistently demonstrated their ability to interpret technical regulations in innovative ways. With the 2027 changes approaching, it remains to be seen what new solutions engineers are developing behind closed doors in their factories as they continue searching for performance advantages.
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