Honda F1 boss Yusuke Hasegawa was confident a few months back about boosting the power of its engine to the level Mercedes enjoyed in 2016.
But the manufacture's bold predictions have obviously fallen short as it struggles to deal with both reliability and performance issues since the season got underway.
Haseagawa plainly underestimated the potential of its new 2017 engine which included a revised architecture which the engineer thought would easily boost its prospects.
"As a matter of fact we were thinking [it was] too easy, and it was too difficult to achieve the new technology - that was my mistake," Hasegawa told Autosport.
"We did some good progress in the mono-cylinder on the dyno, but as soon as we complete the V6 engine we had many issues.
"What we achieved in mono-cylinder is at a very good level, but when we transfer exactly the same specification to the V6 engine it doesn't work.
"We are very disappointed. But it was too late that we noticed that - at Christmas.
"After we understand the issues this was the time we need to confirm the final specification - we needed to have some compromise."
Installed in the back of McLaren's new MCL32, Honda's engine also produced massive vibrations which impaired the entire package.
"We have huge vibrations," added Hasegawa.
"The only thing I can tell is that on the dyno we didn't have such a big issue - when we have a gearbox, driveshaft and tyre it has some resonance.
"I'm not blaming the chassis; we have to realise the situation on the dyno as well."
As units in Great-Britain and Japan work around the clock to solve its persistent troubles, Honda is working on an upgrade package tentatively scheduled for introduction at the Spanish GP in Barcelona in May.
"If we find a good solution we need to change the engine for round five or six, so I really want to update our specification before then, or to that time," he said.
"We have already achieved some good level of performance with the mono-cylinder engine. The thing we have to do is transfer that technology to the V6.
"Although we still have to improve that, we have some confidence we can achieve that level."
GALLERY: F1 drivers' wives and girlfriends
Keep up to date with all the F1 news via Facebook and Twitter
