Eric Boullier is confident that McLaren would have won races in 2016, had it been racing with a Mercedes engine.
McLaren has been running Honda power units since 2015, which has trailed incumbent manufacturers Mercedes, Ferrari and Renault in terms of both power and reliability.
Although the Japanese manufacturer made significant strides this season, it is still some way off its nearest challenger.
While much remains to be desired on the engine side, Boullier feels McLaren chassis was good enough to take race wins.
"If we had the best engine this year, we would have won races," Boullier told Autosport. "We know, the GPS traces [of corner speeds] tell us.
Boullier believes the chassis and engine are so tightly integrated in F1’s hybrid era that any development on one side will have a positive impact on the other.
"There is room for improvement everywhere with Honda," he said."It also drives your chassis development. Everything is connected.
"You can't make a car too draggy if you don't have enough power deployment because you lose time.
"You have to balance all the time. We work as one team with Honda to achieve what we want."
Boullier reiterated how difficult it is for a manufacturer like Honda to catch up with rivals who have been developing V6 Hybrids for 5-6 years.
"The gap has closed," he said. "But to get where Mercedes is, you can't just copy and paste.
"There is a way you have to go through. You can't do it in three months or six months but in a few years.
"It took Renault time [to make engine gains] and still today, they are not on top of the game. They started to develop this engine six years ago."
McLaren hasn't won a race since the 2012 Brazilian Grand Prix, it's longest dry spell in Formula 1. It's best finish this year was a pair of fifth place finishes in Monaco and Japan.
by Rachit Thukral