Ahead of Formula One winter testing at Barcelona, the FIA is set to hold a meeting with technical experts as attention grows around a potential engine loophole linked to the new 2026 power unit regulations. Even before the first cars run collectively on track, debate has already intensified around how the rules are being interpreted.
At the centre of the discussion is the compression ratio of the internal combustion engine. This refers to the ratio between the cylinder’s maximum and minimum volume and plays a key role in efficiency and performance.
Under the outgoing regulations, the compression ratio was set at 18 to 1. For 2026, that figure has been reduced to 16 to 1. One of the aims of the change was to make the power unit regulations more accessible to new manufacturers entering the sport.
The controversy emerged after it became clear that Mercedes, and to a lesser extent Red Bull Powertrains, may be able to pass the FIA’s static checks while still achieving a higher compression ratio in real world running conditions. The suggestion is that once the engine reaches higher operating temperatures on track, the effective ratio could exceed the stated limit.
The current regulations outline how this measurement is handled. Article C5.4.3 states that no cylinder may have a geometric compression ratio higher than 16.0, and that the measurement procedure is carried out under static conditions at ambient temperature. Each power unit manufacturer defines the procedure in line with FIA guidance, with approval from the FIA technical department as part of the homologation process.
Teams operating within those parameters argue they are fully compliant. From that perspective, if an engine meets the static test requirement, any change in behaviour once running falls within the existing wording of the rules.
However, other manufacturers have taken a different view. Audi, Ferrari and Honda point to another section of the regulations, Article C1.5, which states that Formula One cars must comply with the regulations in their entirety at all times during a competition.
Their argument is straightforward. Since the 16 to 1 compression ratio is explicitly written into the rules, it should apply not only during static checks but also while the engine is running on track. From their perspective, any interpretation that allows a higher ratio under operating conditions undermines the intent of the regulation.
For now, the FIA appears inclined to maintain the current measurement approach. The governing body has indicated that it is not planning immediate changes before the start of the season. At the same time, it has not ruled out clarifications or adjustments further down the line if they are deemed necessary.
The issue will be discussed again on 22 January, when the FIA hosts a scheduled meeting with technical experts ahead of the first day of pre season testing at Barcelona.
An FIA spokesperson addressed the situation, stressing that the meeting is part of a broader process rather than a reaction to a single controversy.
“As is customary with the introduction of new regulations, discussions on the 2026 iteration covering power unit and chassis are ongoing,” the spokesperson said.
“The meeting planned for 22 January is between technical experts. As always, the FIA assesses the situation in order to make sure the regulations are understood and applied in the same manner between all the participants.”
The FIA has also clarified that the meeting was planned well in advance and is not solely focused on the compression ratio issue. The agenda includes discussion of the new chassis regulations, although it is expected that the engine topic will dominate conversation given the implications.
As is often the case in Formula One, those who have identified a potential grey area view their interpretation as fully legal, while rivals push for greater clarity or tighter wording. With the FIA choosing not to intervene at this stage, any immediate changes before the opening race appear unlikely.
If adjustments are made, they are more likely to be aimed at 2027 or, in the earliest scenario, around the summer break. That timeline reflects the complexity of power unit development and the need to avoid destabilising the competitive order mid season.
There is, however, an existing mechanism within the regulations designed to protect manufacturers that fall behind. The Additional Development and Upgrade Opportunities system allows extra upgrades for those lacking internal combustion engine performance.
Power output is measured across three blocks of races, rounds one to six, seven to twelve and thirteen to eighteen. Manufacturers that are between two and four percent down on the leading engine receive one additional upgrade. Those more than four percent behind are allowed two additional upgrades.
Even with that safety net, adjusting compression ratios is far from simple. Changes of that nature affect combustion behaviour, reliability and overall engine architecture. It is not something that can be corrected quickly, even when upgrades are permitted.
That reality explains why Audi, Ferrari and Honda continue to push for changes to the measurement procedures or, at the very least, clearer guidance on how the maximum compression ratio will be enforced going forward.
As Formula One prepares to enter a new technical era, the debate highlights a familiar truth. The rules may be written in black and white, but their interpretation often decides who starts the season with an advantage.
