Honda is on a "very short timeline" as it continues reliability testing for its 2026 Formula 1 engine for Aston Martin to address issues that need to be resolved.

The new Aston Martin-Honda works partnership has a huge amount of expectation attached to it, especially with F1 design legend Adrian Newey now leading the team.

However, it has also been subject to a lot of speculation since 12 months ago, when doubts about it 'struggling' to be ready for the new rules were first suggested.

Getting on top of the new engines - which are an almost 50/50 split between internal combustion and electric power, place a huge emphasis on energy recovery and deployment, and have lost the MGU-H as part of that process as well as assisting the turbocharger - is a major challenge for all manufacturers.

Honda also had to catch up on time lost at the start of the project because it only announced its Aston Martin deal in May 2023, and before then had only had a skeleton research and development team at its Sakura facility looking into the 2026 rules due its previously announced F1 withdrawal.

"The regulations in 2026 are very challenging," Honda Racing Corporation president Koji Watanabe said at Honda's engine launch event in Tokyo on Tuesday.

"It's difficult. It's challenging. That's why we would like to take it on.

"Currently, Sakura is also working hard on the reliability testing, and working on a bench testing, and we want to really bring onto in-vehicle testing.

"We are running on a very short timeline, but we want to make sure that we are fully prepared for it."

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Aston Martin executive chairman Lawrence Stroll, who said that "our journey won't always be easy and challenges inevitably lie ahead", called the recently repurposed Andy Cowell an "instrumental" part of making the works partnership as effective as possible.

Cowell, who is now Aston Martin's chief strategy officer having previously been CEO and team principal, said getting a car and engine package to perform and be reliable is "always a challenging time".

"There's a huge amount of development testing going on, both at Silverstone [at Aston Martin's factory] and the same in Sakura," said Cowell.

"And we've set tough targets. We want to win, but we understand that Formula 1 is the pinnacle of motorsport, and it's difficult, it's challenging, and you focus on your issues.

"It's very rare that engineering organisations celebrate successes in the factory. So we are working hard on all the issues that we need to resolve.

"And we will go to Barcelona, and we will learn about the car on the track, and we will go to Bahrain twice, and we'll learn about the car on the track. And then we'll end up in Melbourne at the first race."

Cowell's position change was widely reported to have come after disagreements since Newey's arrival as managing technical partner - with Newey subsequently succeeding Cowell as Aston Martin team principal.

Cowell has now been credited with having oversight of the engine side of the equation, getting Honda, new fuel partner Aramco and lubricant supplier Valvoline to work together effectively.

This collaboration, especially the contribution of first-time F1 fuelmaker Aramco, is a big question mark over the final performance level of the engine.

Watanabe hinted that it is still in a relatively early stage of being optimised.

"We are working with a new partnership with new fuel, new lubricant," he said.

"So in all of these situations, we want to build up what we have bit by bit, learn as much as we can and be prepared for it."

A significant early engine topic for 2026 has been discussion around the new reduced compression ratio for this year, and a potential advantage Mercedes and to some extent Red Bull Ford Powertrains are thought to have derived.

Honda is among the manufacturers to believe that Mercedes and Red Bull may be achieving a higher compression ratio than the rules allow.

The compression ratio, reduced from 18:1 to 16:1 for the new rules, relates to the volume differences in any engine cylinder between when the piston is at its lowest and highest points.

It is measured when the engine is not running and while several manufacturers, including Honda, are arguing the ratio can never be more than 16:1, the counterpoint is the rules relate to the measurement in static conditions and ambient temperatures so it is fine to achieve a higher compression ratio when the engine runs and metals expand due to the heat.

"Compression ratio is clearly a key thermal efficiency enabling aspect of an internal combustion engine, so you always push it to the limit," said Cowell.

"I'm sure every single power unit manufacturer is doing that. And the FIA have the job to to make sure that everybody interprets the regulations in a fair and equal way, which is what's ongoing at the moment."

There will be a meeting to discuss the matter this Thursday and Honda CEO Toshihiro Mibe said it has its own clarifications to get from the FIA too.

"Regulations do not have everything listed very clearly, bit by bit," Mibe said.

"So in the new regulation, we look into the possibility of the new technology for each of the different power units.

"There is a lot of room for interpretation as well, and this is a part of the race. So for the FIA, it's up to them to decide on whether it's good or bad.

"For Honda, we have a lot of different ideas, and we would like to discuss with the FIA to understand if our ideas are accepted or are not OK.

"That's how we're going to proceed."