Adds comment from other bosses, detail

By Alan Baldwin

SAKHIR, Bahrain, Feb 27 (Reuters) - Red Bull Formula One boss Christian Horner has expressed support for an eventual return to V10 engines despite his team spending heavily on designing their own power unit for the new era starting in 2026.

The naturally aspirated V10s, which disappeared from the starting grid in 2006, are far louder than the current V6 turbo-hybrid units but are being mooted as a future option with sustainable fuel.

The noise from the current whistling V6 turbo-hybrids measures in the region of 130 decibels against at least 140 for the high-revving V10s, whose blast can cause hearing loss and is comparable to an airliner taking off.

The governing FIA said last week that discussions were ongoing with stakeholders over the sport's technical direction from 2030 and a working group was likely to be set up to explore all possibilities.

"Personally, from a sporting perspective, looking at what the future engine of Formula One should be beyond this next generation, particularly with the way that sustainable fuel is going, it does open up all kinds of opportunities," said Horner.

"Inadvertently, we’ve ended up with a very, very expensive, very complex engine from '26 onwards.

"The purist in me would love to go back to a V10 that was done responsibly with sustainable fuel that reintroduced the sounds of grand prix racing," he added at pre-season testing in Bahrain.

"It's an interesting concept and one to certainly look for after this current set of regulations."

Red Bull, who will be partnered by Ford from 2026 after a split from Honda, have built a powertrains plant next to their Milton Keynes headquarters.

Former Mercedes engine chief Andy Cowell, now the team principal at Aston Martin, acknowledged debate in the background but said the main excitement was about the next generation of power units.

Mercedes team boss Toto Wolff agreed the sport should talk up the immediate future.

"We are pushing the boundaries of battery technology and for sustainability it's the first year we're having 100% sustainable fuel," said the Austrian. "Nobody knows where all of this is going to pan out.

"F1 is trailblazing. All of the stakeholders should be really cheering for this and make sure the sport is perceived in such a high tech way as it needs to be...

"At the moment I think it (V10 talk) is a bit premature and we are at risk of diluting the message to the world the year before getting started with these new exciting regulations if we talk about something that comes later."

(Reporting by Alan Baldwin, editing by Peter Rutherford and Toby Davis)

((alan.baldwin@thomsonreuters.com; +442075427933;))