Valtteri Bottas says an issue on his first-timed lap during opening practice for the Hungarian Grand Prix resulted in his Mercedes Formula 1 engine going into a “safety mode”.

Bottas was forced to return to the pits after encountering an issue with his Mercedes power unit on his opening run in FP1, resulting in the German manufacturer carrying out a precautionary engine change, meaning the Finn missed the rest of the session while it swapped to another PU within his engine pool.

“During the first timed lap I got an issue with the engine, lost some power and had some misfiring and eventually it went to safety limp home mode,” Bottas explained.

“They couldn’t find the issue immediately and that’s why we decided to swap the power unit for practice two in the hope for more laps but in the end we didn’t get any.

“So like three proper timed laps in the dry and a couple in the wet. So not many laps today but it’s fine. But at least the time I was in the car I felt good.”

Bottas was only able to complete a total of 20 laps throughout Friday as rain disrupted the afternoon session when he finally returned to track action.

Asked how much the rain affected Mercedes’ run plan, Bottas replied: “It affected it quite a lot.

“We got a few laps in at the beginning on the dry but even then it was small drizzle. But got a feel of the car balance and a feel for some of the things we need to work on for tomorrow.

“It’s a shame it was between inter and dry conditions for most of practice two so couldn’t run much.

“It felt a lot better [than Germany],” he added. “I think the set-up of the car is quite different here and it felt a lot better and more grip in general, the balance was better.

“Just looking at the laptimes we were doing at the end with the other cars at the same time, it was quite decent.

“For sure there is plenty of data from Lewis as well I can look at too and lots of learnings to do even if there was not much running.

“But looking forward to get it properly started tomorrow.”