Yamaha confirms it overrevved its engines at Mugello
The engine failures suffered by Valentino Rossi and Jorge Lorenzo during the Italian Grand Prix were caused by an electronic issue that made the units overrev, Yamaha confirmed on Thursday.
In the Italian's case, the engine of his M1 blew up on the ninth lap of the race, while he was running in second right behind Lorenzo, who had suffered another failure just a few hours earlier in the warm-up.
As revealed by Motorsport.com, the cause of the problem was the overstraining that the engines were subject to at Mugello, especially in the undulation on the main straight.
After the race, both engines were sent to Japan, where the engineers carried out an extensive analysis of what happened.
"The failures were caused by an electronic issue related to the rev limiter, which ultimately resulted in valve and piston damage," said Yamaha's YZR-M1 project leader Kouji Tsuya.
"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 overrev 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.
"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 learned 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."
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