Power unit manufacturers will meet with the FIA on January 22 to discuss the compression ratio issue. Mercedes and Red Bull Powertrains appear to be able to exceed the 16:1 limit under operating conditions, a value that must be measured at ambient temperature. Some rivals are now pushing for additional checks to prevent potential protests.
Mercedes and Red Bull Powertrains currently feel completely protected. The solution that allows their power units to increase the compression ratio beyond the nominal 16:1 permitted by the 2026 regulations is fully compliant with the way the rules have been written. The checks must be carried out at ambient temperature, therefore with the engines switched off, while once running, the units seem to return to around 18:1, the previous limit.
It is said that checks cannot be performed with the engine hot, not because there are no suitable technical tools to do so, but simply because the regulations have been written in a way that prevents the reading of these data. With the introduction of the new FIA regulations, an important parameter was changed: inside the combustion chamber, the sensor sampling frequency was reduced to 1 kHz (one thousand cycles per second), specifically to prevent pressure peaks from being detected. This decision was taken to stop engine manufacturers from precisely monitoring detonation and pushing development to extremes, with huge costs in the pursuit of performance. A choice made with a positive intention has nevertheless opened the door to an issue that is becoming increasingly… hot.
Mercedes and RBPT comply with chapter C5.4.3 of the technical regulations, while other manufacturers argue that there is a breach of Article 1.5, which states that cars must be compliant at all times during a race weekend.
It would have been sufficient to replace the combustion chamber sensor with one that allowed the FIA to read pressure peaks in order to measure the compression ratio, especially considering that the technical delegates have access to the CAD drawings of each individual project.
However, unanimity was required and was not achieved. As a result, Mercedes and Red Bull currently retain a competitive advantage estimated at more than 10 horsepower. The figures being discussed suggest around 0.20 milliseconds per horsepower, equating to a gain of a couple of tenths per lap. Mercedes is also believed to have extensive written correspondence with the FIA, in which the International Federation would have approved the solution developed in Brixworth.
According to Red Bull Powertrains managing director Ben Hodgkinson, “…a lot of noise is being made about nothing. I am confident that what we are doing is legal”.
At the upcoming engine manufacturers’ meeting scheduled for tomorrow, January 22, which will also include the sporting directors, the compression ratio topic will be on the agenda. Some parties are threatening to lodge a protest at every Grand Prix if no action is taken, challenging the solution devised by Mercedes and adopted by RBPT, which they believe does not respect the spirit of the regulations.
Mattia Binotto, however, has taken a less drastic stance. The head of Audi F1 admits: “I don’t think clarity will be achieved or a compromise will be found. The January 22 meeting will be used to discuss with the FIA how to improve or develop a methodology to measure the compression ratio in operating conditions in the future”.
The message is clear, but some suggest looking at NASCAR and SCCA, where such checks are carried out, and potentially developing an already existing technology. American company Katech Engineering, for example, has the Katech Whistler, a tester that can be fitted in place of a spark plug to carry out an instant check with the engine hot and running at the correct speed. It does not appear to be calibrated for Formula 1 power unit values, but it could be developed further.
It will be very interesting to see what stance the manufacturers take following tomorrow’s meeting, in order to understand what kind of start to the season we should expect.
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