COMPRESSION RATIO: SHADOWS OVER THE NEW MERCEDES AND RED BULL ENGINES

As tradition dictates in Formula 1, every regulatory overhaul brings with it not only promises of renewal, but also the reappearance of creative interpretations of the technical rulebook. This time, however, the debate has ignited even before the new cars have turned a wheel on track. At the center of attention are Mercedes and Red Bull Powertrains, allegedly involved in a controversial issue concerning the 2026 engines.

The upcoming season will mark a clear break with the past. The cars will be radically different from an aerodynamic standpoint—with ground effect gone and movable aerodynamics introduced—while the power units will be even more transformed, as the electrical component takes on an unprecedented role in overall performance. Yet, contrary to what usually happens, the first battleground is not aerodynamics, but the internal combustion engine itself.

The regulations stipulate that the compression ratio of the new engines must be reduced from the current 18:1 to 16:1. A change that may seem minor on paper, but one that carries significant implications for efficiency and performance. According to reports from the German outlet Motorsport Magazin, Ferrari, Honda, and Audi have formally requested clarification from the FIA, suspecting that some competitors may have found a way around this restriction.

Mercedes and Red Bull Powertrains—set to make their debut as a full-fledged engine manufacturer with technical support from Ford—are said to be under scrutiny. The theory is that both may have developed solutions based on special materials capable of altering their physical behavior at high temperatures. Under operating conditions, these materials could expand, effectively increasing the compression ratio and bringing it back close to 18:1.

The regulatory gray area stems from the fact that compression ratio checks, as outlined in Article C5.4.3 of the technical regulations, are carried out with the engine static and at ambient temperature. If the variation occurs only at operating temperatures, the engine would appear compliant during inspection, while potentially violating Article 1.5, which requires the car to be legal at all times throughout a race weekend.

To understand the significance of the issue, it’s worth recalling what the compression ratio represents: it defines how much the air-fuel mixture is compressed inside the cylinder, from bottom dead center to top dead center of the piston. It is a critical parameter for engine efficiency and power output. Estimates suggest that such a solution could yield up to 15 additional horsepower from the internal combustion engine alone, translating into an advantage of nearly three tenths of a second per lap.

For the FIA, the main challenge is a practical one. At present, there are no tools capable of accurately measuring the compression ratio with the engine running and at real operating temperatures. This makes any immediate intervention extremely difficult, if not impossible. Moreover, even if the suspicions were confirmed, rival manufacturers would have little time to react, with the season already just around the corner.

A far from straightforward start to a new regulatory cycle that has already generated uncertainty and controversy. Once again, Formula 1 finds itself walking the fine line between technical innovation and aggressive interpretation of the rules.

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