Power unit development has been opened up in F1 for 2017, with the token system removed so manufacturers have much more freedom through the course of the year.

But with the current hybrid engines expensive to develop, Renault Sport Racing president Jerome Stoll believes spending needs to be kept under control.

"Hybrid is something which is interesting, the problem we have at the end of the day is the cost of the technology," Stoll told Motorsport.com.

"We have to take care of the costs and ensure that there is a return on the investment that we've made. And the costs have deviated a lot.

"We have to see how we can curb a little bit or cap a little bit the costs of development for each car maker."

In response to repeated calls for F1 to go back to simpler, louder engines, Stoll agreed with FIA president Jean Todt's belief that a technologically advanced formula is required to maintain manufacturer interest.

"You have to take into consideration that if we are in this competition it's also for technological reasons," said Stoll.

"The fact that we pushed among the others for the introduction of the hybrid system in the engine is also because it shows that even in the competition of F1 we can work for the environment by reducing the consumption by 30-40 percent.

"It's something that illustrates that you can be in this competition without being somebody who wants to kill the planet.

"You like the competition, you like the passion, and you can work also in a way where everybody wants you to work."

Red Bull motorsport advisor Helmut Marko believes F1 engines should be made loud again, but he does not want the current engines to be made louder artificially.

"Nobody will buy that," he said of finding a way to increase the noise from exhausts.

"We need to have proper engines again – engines that are a violent force with noise that makes you feel exactly that.

"The driver has to be the crucial factor again, not the engineer. This has to happen. I want to admire a person who's doing an extraordinary job."