Over-Revving Caused Yamaha's Mugello Engine Woes

Yamaha have issued an official explanation for the problem they suffered at Mugello, which saw Valentino Rossi’s engine blow up during the race, and Jorge Lorenzo’s engine blow up during warm-up on Sunday morning.

The cause given is exactly in line with the reasoning in our Mugello Sunday post-race round up: the engine overrevving as the rear wheel lifted at the end of the Mugello straight.

At that point in the track, with the bike hitting 350 km/h and nearing peak speed at top gear and at full throttle, when the rear wheel lifts over the crest at the end of the straight, the engine spins up too quickly for the rev limiter to catch.

Yamaha MotoGP project leader Kouji Tsuya acknowledged they had been caught out by the new unified software package: they had used similar settings to last year, but the rev limiter with the 2016 electronics had not reacted as quickly as Yamaha’s proprietary software was capable of in previous years.

That caused engine damage at the end of the straight, eventually causing the engine to fail completely with piston and valve damage.

Because of the nature of the damage, and the difficulty in locating the precise nature of the problem, Yamaha were unable to put in a fix for both factory Yamahas for the race at Mugello after Jorge Lorenzo’s bike had blown an engine on Sunday morning.

The engine that Rossi blew up was his third engine, a relatively fresh engine, as was Lorenzo’s engine that blew. Lorenzo eventually raced his second engine, which had been in action since Qatar, and had 25 practice sessions and 2 races on it.

Yamaha’s statement says that they have identified the problem and have a fix in place from now on. In part, the risk is lower, as there are no other tracks coming up with such unique conditions as Mugello.

But it is entirely possible that part of the fix is lowering the maximum revs on the engine a fraction (perhaps just 50 or 100 revs) to avoid a similar problem. That should not have a material effect on the performance of the bike.

This article was originally published on MotoMatters, and is republished here on Asphalt & Rubber with permission by the author.