The Japanese manufacturer endured a difficult start to 2017, with a lack of power and poor reliability hampering its efforts and threatening its future partnership with McLaren.

Although it has made some progress since – finally scoring its first points of the year at the Azerbaijan Grand Prix – it is still facing big pressure to make further gains.

Reflecting on the season so far, Honda's F1 engine chief Yusuke Hasegawa said his company had been aware that progress on the power front had not been as big as had been hoped before pre-season testing, but it was the reliability factors that especially caught it out.

In an interview published on Honda's F1 website, he said that it was only when the company's 2017 engine ran on track for the first time that it became aware of the extents of the troubles it had.

"Many items we could not test on the dyno, so it is normal that we need to check some functions in the car," he said.

"The oil tank is one of the biggest items, so we have a rig for the oil tank but we cannot recreate the same types of G-forces and conditions as in the car.

"Of course, by design we have to consider the actual car situation in theory, but sometimes it is not always the same situation so that is why we had some issues with the oil tank first.

"The second issue was down to the vibrations. On the dyno, the model is stiffer and heavier, so it doesn't create any synchronised vibrations, but on the car - with the gearbox and the tyres - there is a much lower level of inertia.

"Low inertia does not always create vibrations but it's completely different from the dyno and that's why we suffered a huge vibration on the car. Of course, we were aware some level of vibration would come in the car but it was much bigger than we expected."

Sticking with concept

While reliability has improved, McLaren is also urging Honda to bring more updates, with Honda's Spec 3 engine having raced for the first time at the Austrian Grand Prix.

Efforts are now focused on a Spec 4 for use later in the year, with Hasegawa saying that the company's decision to stick with the same split turbine and compressor concept for next year meaning it can push until the end of the campaign.

"We don't stop developing, we need to keep updating," said Hasegawa. "Of course the performance and results are the most important things but it's all learning for the future too.

"Compared to last year we needed to modify the engine concept, but next year we will keep the same concept.

"It's good that we can use the same concept because this year's development and improvement is directly connected to next year. So that means we don't need to stop the current development, and from that point of view we have already started next year's design."