Big performance steps with the power unit are becoming difficult to find this far into the current regulations, according to Honda’s Formula 1 technical director Toyoharu Tanabe.

Honda returned to F1 a year after the introduction of the V6 turbo power units, joining forces with McLaren in 2015 but struggling for three seasons before that partnership ended. Since working with Toro Rosso and last year adding Red Bull, Honda has made clear progress to close the gap to the other power unit manufacturers but Tanabe believes the best way of finding performance now is though marginal gains across a number of small details.

“We could show our improvement, our good positive progress this year, not only with Red Bull but also Toro Rosso,” Tanabe told RACER. “It was very nice for all the people working for this project and people in Honda. So I want to keep this momentum for next year. The development for next year has already started. And then we need to push more to achieve our goal.

“I think it’s harder than previous years. We need to be precise in every single area, in terms of hardware, also software and then trackside management as well. So, we keep pushing. The PU means the ICE, MGU-H and K, and all the systems, water and oil. Also tools, software, we have a lot of things to do. But a big step? Maybe that’s getting difficult.”

One area Honda has made clear progress in recent seasons relates to reliability: neither Red Bull not Toro Rosso suffered a race-ending problem due to the power unit during 2019. However, Tanabe says that doesn’t mask the fact that reliability still needs to be worked on.

“We achieved no Sunday race failure to stop the car,” he said. “It was good for us. But like (Verstappen’s) situation (in Abu Dhabi), we still have not a stoppage, but we still have an area to improve. Also we had some issues in practice. So we need to clean up everything from the race weekend.”

Honda will again power both Red Bull and Toro Rosso next season, and recently extended its supply contract for a further year to include 2021.