In just under a month, the FIA will unveil the first set of ADUO data, offering power unit manufacturers the opportunity to unlock new development options. However, FIA single-seater director Nikolas Tombazis has revealed an important behind-the-scenes detail: when defining how to measure engine power, the governing body had initially pushed for a more advanced system that would also factor in secondary parameters, but the manufacturers ultimately rejected the idea.
There is a crucial phase in the early part of the season that could mark a turning point, namely the few weeks between the end of May and the beginning of June. Following the Canadian Grand Prix, the FIA will analyse and publish the ADUO data, a system specifically designed to give power unit manufacturers that are trailing behind a chance to reduce the gap through targeted concessions.
These concessions include additional financial resources, more dyno testing hours, and, most importantly, the ability to homologate engine upgrades during the current season rather than waiting until the end of the year. Each manufacturer already has its own internal analysis and an estimate of its deficit relative to its rivals and the benchmark engine, but it will ultimately be the FIA’s assessment that determines whether ADUO support is activated.
Once the governing body publishes the results—based partly on data collected from on-track performance—manufacturers will receive confirmation of their deficit band compared to the reference engine, which is widely expected to be the Mercedes unit. The first band places the gap between 2% and 4%, equivalent to around 12 horsepower, while the second band applies to those trailing by more than 4%, a category that Honda is almost certain to fall into. The higher the deficit band, the greater the concessions granted to help close the gap.
However, one key point must be kept in mind: this is not a Balance of Performance system like the one used in the World Endurance Championship. In Formula 1, there will be no forced equalisation. Instead, manufacturers are simply given tools and allowances to move closer to the benchmark engine. It then becomes the responsibility of the engineers to make effective use of the additional resources unlocked by the ADUO without wasting development potential.
No changes: ADUO will only come into effect after Canada
To ensure fairness and allow manufacturers to close the gap gradually, the FIA regulations define six-race evaluation windows. At the end of each cycle, the results are published. This mechanism ensures that updated data is available every six Grands Prix, providing a continuous and accurate picture of performance trends throughout the season, where values can shift significantly.
The first controversy surrounding ADUO this year has been linked to timing. The Bahrain and Saudi Arabian Grands Prix, which were cancelled due to geopolitical tensions in the Middle East, could have influenced the technical calendar. Some stakeholders pushed to bring forward the introduction of ADUO by counting the cancelled events, in order to have a clearer performance picture ahead of Miami.
However, as confirmed by Nikolas Tombazis, both Miami and Canada will remain key milestones in completing the evaluation process. The cancelled races were not counted, meaning that the FIA will wait until the sixth actual round of the championship before publishing its findings.
“At the moment we are still evaluating the ADUO. We have at least one month before the first batch of ADUO results, so we have Miami and certainly also Canada,” Nikolas Tombazis explained.
The FIA wanted a more complex system, but teams said no
At its core, the ADUO system is intended to prevent a prolonged and overwhelming dominance similar to what Formula 1 experienced in 2014. But what parameters are used in these measurements? The FIA will evaluate only the power output of the internal combustion engine, meaning the thermal component of the power unit, while the electrical side will not be taken into account.
This leads to a second challenge: how do you accurately calculate pure engine power when performance can be influenced by secondary factors such as plenum temperature or turbocharger size, which vary from one manufacturer to another depending on design philosophy? It is well known that some manufacturers have opted for smaller turbochargers, which improve drivability and performance in the initial acceleration phase, but may theoretically limit peak power output.
It is therefore no surprise that debates have already emerged even before the official publication of the results. Mercedes, for instance, has strongly reiterated that ADUO should remain a tool to reduce performance gaps, rather than becoming a mechanism that allows one manufacturer to leapfrog another.
These concerns had already been considered by the FIA. In fact, during the spring of last year, the governing body proposed incorporating some of these secondary parameters into the measurements, creating a more sophisticated calculation system. However, the teams opposed the proposal.
“It is very clear that pure engine performance in terms of horsepower is influenced by important but secondary parameters such as plenum temperature, the turbo or even exhaust pressure. There are various factors that affect engine performance,” Nikolas Tombazis explained.
“We offered engine suppliers, roughly a year ago, the possibility of having a slightly more complex formula where these parameters were also included. At the time they were quite categorical in saying they did not want it, so at the moment we are without corrections of this nature, and the regulations clearly state that only engine power is considered.”
ADUO evaluation also relies on on-track car analysis
The regulations do not publicly specify exactly how ADUO measurements are carried out, as the details are contained in a separate document accessible only to the teams. However, it is known that the FIA uses multiple tools to evaluate internal combustion engine performance, ranging from factory dyno data to telemetry gathered on track.
In race conditions, the governing body analyses the best-performing car from each manufacturer over a series of laps, generating statistical data that can be compared across multiple events. This approach ensures a robust dataset and reduces the impact of anomalies.
Looking even more closely, certain phases of a lap carry greater weight when assessing engine performance. For example, more importance is given to the beginning of a straight, where the driver demands maximum power, than to the end of the straight, where aerodynamic drag and car characteristics play a larger role in determining top speed.
This methodology has already been shared with the teams, which in turn conduct their own independent comparative measurements to support development work.
“Obviously, power is calculated in a weighted way over the lap, so the areas where power is more important carry more weight than those where it is less critical. Typically, the beginning of a straight is more important than the end of the straight, for example,” Nikolas Tombazis added.
“For each race, we take the best car from each engine supplier, we lose many laps to build an average, so we have a fairly reasonable statistical approach that we have discussed and shared with the teams. We also have significantly improved sensors this year compared to previous seasons. Therefore, we believe the measurement will be quite accurate.”
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