SAKHIR, Bahrain -- Honda admits it does not know the exact cause of its latest spate of reliability woes after McLaren suffered three MGU-H failures over the course of the Bahrain Grand Prix weekend.
After Stoffel Vandoorne suffered a problem in Friday practice, Fernando Alonso was not able to take part in the second part of qualifying due to a failure on his car. All the problems have been traced to the MGU-H, which is the part of the power unit that harvests energy from exhaust gasses via the turbo and can be used to control the speed of the compressor.
"We are not sure the exact cause, but definitely a mechanical failure of the MGU-H - something around the bearings was sticking and it happened three times here," Honda engine boss Yusuke Hasegawa said. "It was very unfortunate.
"We are not sure why it has happened just here three times. But we suspect something has happened in this circuit or environment or characteristics. Possibly because the temperature is very high and the conditions are very sandy, but we don't know the cause."
The problem on Alonso's car will require a full power unit change ahead of Sunday's race and Vandoorne's issues means he has now used three of his allotted four turbos and MGU-Hs for the year. Hasegawa confirmed the failed parts were beyond repair and would not be used again this year, but is hopeful the MCL32 will complete a race distance on Sunday.
"Fernando will use a new MGU-H and Stoffel also a low-mileage one, so I think we will be alright tomorrow."
But Alonso, when asked about the drivability of the engine on a good lap, was less optimistic.
"There is no point for us to talk about drivability if we cannot complete a lap or do the qualifying. I don't really care too much about the drivability if I cannot finish a race so far this year or finish the qualifying now.
"It's hurting. We had the possibility to be a couple of places better and now we have to fit a new power unit tomorrow without the perfect settings and no warm-up or laps to set the engine, so we will probably have a difficult race."