Despite talk of the new F1 engine regulations bringing rumours of increased manufacturer interest, speculation that Honda and Toyota may lead the arrivals has been dismissed by one leading engine specialist.

The 2014 F1 season will see the enforced switch from the current V8 units to 1.6-litre turbocharged V6s and, while the likes of Ferrari, Renault and Mercedes are all committed to the change, many others have been mentioned as possibly joining them.

Honda has been strongly linked to a renewed partnership with McLaren, while Toyota was also recently named as showing interest in a return. Although the story about the company using its Lexus brand for the purpose appeared on 1 April and was largely passed over as a spoof, the F1 paddock in Bahrain was awash with suggestions that the marque was eyeing a new tie-up with Williams that could bring Kamui Kobayashi back to the top flight. Audi and Porsche are constantly being connected to an F1 programme, while both Cosworth and the Craig Pollock-headed PURE operation appeared to have come and gone as contenders.

According to Renault's Rob White, however, only the currently involved manufacturers are likely to be involved when the new era kicks off next season, with interest elsewhere having waned as the time to commit got closer.

"The first project meetings were held four years ago, and the interest was great, with Audi, Cosworth, Ilmor, Honda, Toyota, Mecachrome and others [present]," the Briton told Germany's Speed Week, "However, as it got more specific, only PURE was left, and now it's only us three.

"If [Honda and Toyota] actually wanted to come back, then why not take part in the planning meetings? I simply cannot imagine that a company will enter in 2015 without having wanted a say in the rules. We have never received a request in this regard. Honda and Toyota could easily ask the FIA for permission and join in, but the meetings are always only Ferrari, Mercedes and us."