New F1 sporting chief Ross Brawn is keen to encourage independent suppliers to come into the sport, an initiative supported by teams such as McLaren and Red Bull, who are looking at future options.

Former Mercedes F1 engine boss Illien, who has stayed in touch with current technology by working as a consultant, has attended recent FIA meetings where the future engine format has been discussed.

A twin-turbo V6 with KERS is the most favoured option, and further studies have been launched.

"Obviously there is a desire to have the possibility for independent manufacturers to come in," he told Motorsport.com. "That's one reason I'm in the meetings, to see whether it's going the right way for an independent.

"It will take a lot of simplification, and we'll have to take a lot of cost out – and make racing better and the sound better. If you have say a standard turbo for everybody, you could take a lot of cost out, for sure."

Illien is adamant that costs have to be brought down in order to encourage new entrants.

"That would be a necessity for independents to have a chance. It's not only the initial costs, it's also the development costs.

"I think everyone will develop and make progress, but the rules should be written in such a way that there is a relatively small gain that you can make with a lot of development."

He also believes that restricting the number of engines allowed per year has increased development costs.

"I think that has to be addressed. Next year, having three engines is more expensive than producing four engines.

"All the new parts you are developing have to go through testing on the dyno, to make sure you have achieved the mileage for three engines a year. And that is expensive.

"I think even four is not enough. We're half way through this season, and half the field has got a problem."

Even allowing for cost reductions Illien says Ilmor won't supply an engine under its own name based solely on having deals with one or two teams, because the funding still wouldn't be sufficient.

"No, I think that's unlikely, because somebody has to fund the initial development costs. Customers are probably not the right way to go, that doesn't pay for it.

"You probably need a manufacturer to support it. But if you look at Red Bull they've got TAG, so it doesn't need to be a car manufacturer, it could be anybody."

Illien suggests that F1 made a mistake by going too far in the direction of road relevance with the current formula, which was introduced in 2014 and will now run to 2020.

"I think road relevance is not that important. In my view, we've got to go racing again. Yes we can benefit road cars to a certain degree, but I think the relevance should be secondary. If nobody is going to watch F1 because it's so boring, it's not the point.

"The MGU-H is one of the very expensive elements, for sure. We might even consider going extreme and go back to normally aspirated engines and KERS. I don't think it's on the table, but I'm sure that spectators would love it.

"Especially as the world is going more hybrid and electric, we need to have something on the race track nobody could have at home."

He also acknowledges that tackling the noise issue for 2021 won't be easy.

"That is a difficult subject, because the more efficient we make an engine, the less noise it's producing. I think we have to compromise a little bit on that. Taking off the MGU-H would help a little bit. The boost level is an issue as well, the more you absorb from the exhaust, the lower the noise level."