Honda had hoped to start F1 2019 with its Spec 2 engine design

The Japanese manufacturer claimed its first podium of the V6 turbo-hybrid era on its debut with Red Bull at the season-opening grand prix and would go on to end a 13-year win drought in F1 in a season in which it claimed three victories.

It introduced three engine upgrades during the year, one more than its rivals, and the Spec 2 that made its debut in Azerbaijan was originally envisioned as the season-starting engine.

However, Honda revised its schedule based on what was realistic long before the campaign started, rather than needing a last-minute change.

"For the power unit development we have a list, and priorities," Honda's F1 technical director Toyoharu Tanabe told Autosport.

"How long does it take? How much we can gain in terms of performance also in reliability?

"Some items take longer, but the step is big. So we just apply [the upgrades] based on that schedule.

"We had a little bit of a delay for the Spec 2 introduction. We wanted to start with Spec 2.

"It's just a result of the PU development [schedule]."

Committing to its revised schedule allowed Honda to spend the winter preparing its uprated 2019 engine for Australia with the knowledge that a stream of upgrades would come in the first half of the year.

Its upgrades started with the reliability-focused Spec 2 in Azerbaijan, a performance-enhancing Spec 3 with a new turbocharger in France and then the Spec 4 - its biggest step of all - after the summer break.

"During this season we started with the Spec 1, and the step to Spec 2 is minor," said Tanabe.

"Then we stepped up to Spec 3, a bigger step than Spec 1 to Spec 2.

"And then Spec 4 was bigger than Spec 2 to Spec 3.

"We are happy to introduce our PU as we promised with the team and drivers, it was almost the same step we could make during the season that we told the team.

"From the trackside point of view, as a technical director at the trackside, I'm so happy with that power unit progress."

Honda has been evolving its engine design year-on-year since a big overhaul over the winter from 2016 to '17 and it intends to keep its engine concept "very similar" for 2020.

The company's F1 managing director Masashi Yamamoto told Autosport that Red Bull helped facilitate Honda hitting its targets this year.

"From Spec 1 to Spec 4, everything went smoothly on schedule, as planned," he said.

"We can say that with Red Bull, a good team, and Max Verstappen, a very good driver who gives us very good feedback, they have powered our development and made it smoother to proceed."