Honda have admitted that McLaren's new engine for the 2017 Formula One season is "very high risk".
McLaren have finished ninth and sixth in the constructors' standings since reuniting with Honda ahead of the 2015 season, as the Japanese manufacturer struggled to keep pace in the F1 development race.
Exciting prospect Stoffel Vandoorne will partner two-time world champion Fernando Alonso at McLaren next season, with a fresh raft of new regulations giving them a chance to even the playing field with the likes of Mercedes, Ferrari and Red Bull.
But the head of Honda's Formula One programme, Yusuke Hasegawa, has warned that a totally revamped power unit does not come with the guarantee of success.
"The concept is completely different," Hasegawa told Autosport.
"It's very high risk, we don't know a lot of things about that new concept.
"We know it will give us a performance advantage but the biggest risk is whether we can realise that potential this year."
He added: "We still have to do some tests and there will be some trial and error.
"I hope we have understood the direction and the elements to focus on."