Why Honda secretly introduced its second F1 ADUO upgrade in Madrid

Honda Racing Corporation president Koji Watanabe has revealed that Honda actually introduced its second ADUO (Additional Development and Upgrade Opportunities) upgrade as early as Formula 1’s Spanish Grand Prix, with the upgrade focused on the power unit's turbocharger.

Aston Martin and Honda struggled from the start of the season, but their performance slightly improved after a major chassis upgrade was introduced at the Hungaroring. In Zandvoort, the team also introduced a power unit fitted with the first ADUO upgrade.

Honda's ICE was measured to be more than 4% behind the Red Bull Ford Powertrains engine, which was rated as having the highest output, meaning Honda was granted permission to use two ADUO tokens during the season.

Honda and HRC had previously explained that they would use only one of those ADUO opportunities. “We used both of them,” Watanabe revealed to Autosport when asked why Honda had decided to use only one ADUO upgrade.

“We introduced the first ADUO upgrade in the Netherlands, and then we put a PU incorporating the second update into Lance Stroll's car at the Spanish Grand Prix.

“The Spec 2 PU we introduced in the Netherlands had some drivability issues, so we introduced an improved turbo at the Spanish Grand Prix.”

Indeed, the FIA's list of PU component usage shows that Stroll's car was fitted with its fifth turbocharger of the season at the Spanish GP. Fernando Alonso's car was also fitted with his fifth turbo, which would appear to be the upgraded version, at the Azerbaijan GP.

Fernando Alonso, Aston Martin Racing

Photo by: Sam Bloxham / LAT Images via Getty Images

Asked whether the objective was to address turbo lag, Watanabe replied: “Yes.” He subsequently explained the thinking behind the staggered introduction of the upgrades.

“It would have been better if we could have introduced everything at once, but it was important to introduce Spec 2 in the Netherlands first. We were also working on measures to address the turbo lag in parallel, so we introduced that in Spain.

“So the application ended up being split between the two.”

Watanabe also said, however, that Honda is still not extracting the full potential of its power unit.

When Honda was previously supplying Red Bull, it was not allowed to introduce performance upgrades, but it continued to use simulations to determine the operating limits of the PU and gradually raise those limits year after year. This was what Honda referred to as “reliability development”.

For example, Red Bull adopted extremely small sidepods in 2024, while also reducing the size of the openings used to draw in airflow for cooling. This was also made possible by raising the PU's operating limits.

“As far as ADUO is concerned, we have used up our opportunities for this season. From here, we will continue working on things that don't involve hardware, as well as developments that will lead into the future”, Watanabe said.

“I don't think we are anywhere near extracting the full performance of the PU. I believe there is still room to improve its competitiveness.

“There were still areas where we were lacking power, so we developed Spec 2 with target figures in mind. We have achieved those targets, so for the remainder of the season, our focus will be on making full use of what we have, rather than continuing to develop the hardware.

“Even so, we want to make sure we are able to fight properly.”