Yamaha Explains Reason Behind Engine Failures at Mugello

Says that an electrical issue related to the rev limiter caused the problem in both cases

Valentino Rossi
Valentino Rossi and Jorge Lorenzo both suffered engine failures during the 2016 Italian GP, Rossi's engine actually failing during the race. Now, Yamaha is suggesting that it was an electric issue that caused the problem in both engines.Yamaha-Racing

All eyes were on Yamaha following the 2016 Italian Grand Prix at Mugello, the Japanese manufacturer having lost two engines on Sunday. Jorge Lorenzo was the first to lose an engine, the Majorcan's bike letting go in Sunday morning warm up, and Rossi the second, the Italian's bike signing off on lap nine of the race.

Now, after having taken each of the engines back to YMC for investigation, Yamaha is saying that both failures were the result of an electrical issue that essentially allowed the engines to over rev, not to any one hard part failing or rider error.

Below, in its official statement, Yamaha explains the issue in greater detail:

After the technical problems in Mugello the two defective engines were returned to YMC for investigation. Following our detailed investigation of the engines, telemetry data and related systems we found the cause of the failures. The failures were caused by an electronic issue related to the rev limiter which ultimately resulted in valve and piston damage. The cause for both Jorge's and Valentino's engine failures was the same. To be clear, there was neither an engine component nor a structural failure, it was purely an electronic control issue.

Valentino's failure was caused by an accidental over rev in acceleration that occurred jumping over a crest with full throttle at the end of the straight. This failure was not in any way related to the mistake made by Valentino at the San Donato corner on the lap before.

There were no special mapping settings used for Mugello; we used the same precise mapping as always. We have now withdrawn both engines from the allocation for the season.

We have a strong history of engine reliability and this fact does not change after this incident; the engines had no problems, but we were not aware of the different behaviour of the standard ECU software, that made the rev limiter work in a different way compared to last year. We set the rev limiter using last year's data in exactly the same way as we did last year, but we could not be aware that the software worked in a different way.

Valentino Rossi at Mugello
Yamaha says that, "Valentino's engine was the freshest of the three that were sealed so far from his allocated engines, therefore after Jorge's Warm Up engine failure there was no reason to consider replacing it."Yamaha-Racing

Valentino's engine was the freshest of the three that were sealed so far from his allocated engines, therefore after Jorge's Warm Up engine failure there was no reason to consider replacing it. Furthermore we couldn't find out the electronic issue in Jorge's engine in such a short timeframe.

Mugello is one of the most critical circuits because of jumping over a crest with full throttle on the straight, and engine RPM becoming higher. We have learnt from this incident and already modified the rev limiter setting, so it will be OK in Catalunya. As a precautionary measure, the other engines used by both Valentino and Jorge in Mugello will be used only for practice sessions, until their life cycles are completed.

We understand an electronic issue caused the failures in Mugello, therefore we do not need to intervene with our remaining engines that are not yet sealed. We still have enough engines for the remainder of the season. We have already devised a countermeasure, so we are confident that the failures in Mugello will not recur.