Cyril Abiteboul won't give much away on Renault's new power unit, but the French team's boss admitted the manufacturer's progress on the engine front has been "substantial".
Renault's engine trailed the units of Mercedes and Ferrari last year and was seen as the weakest component in Red Bull Racing's package.
However, sustained development work and a new design are providing Abiteboul with a bullish outlook for 2019.
"No figure - but it is substantial," he said, when asked by Motorsport.com about the new engine's level of improvement.
"The furthest I will go is that it is the biggest we have ever done since the V6 introduction.
"It is very much new, and it is just pushing further the concept that we introduced and tested successfully with Red Bull – the famous C-spec that we elected not to run.
"But it is okay, because we had enough information and enough feedback by getting it on the Red Bull. It has really been pushed much further with this year's engine."
Renault's enters the fourth year of its five-year plan to bring it back into the winner's circle. That roadmap should see the team fighting for podiums next season, but Abiteboul is hoping Renault can offer a glimpse of its ambitions to its front-running rivals in the next ten months.
"In order for the progression to keep on continuing to be here, we need a number of success stories," he said.
"Last year the progress in the championship was in general a success story, and I think it is fair to say that more progress in the championship will take a bit longer.
"That is very clear. We are humble and professional enough to know that.
"But I think it is important to have some glimpses or demonstrations that our ambitions are correct.
"I would like and I believe that in particular this can come from the engine side, where we have had in particular a very, very strong winter. So that will be typically a good season.
"On the chassis side, the Enstone side, we have the structure but it is going to take a bit of time before the structure can turn into a race winning car."
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