Romano Albesiano, Aprilia's technical manager in MotoGP, has just announced it: the brand new engine from the Noale firm which will line up in 2020, a 4° V90, will have an external flywheel.
Why, and especially where the competition is, here are the points that we suggest you address in this article.
The flywheel is a metal mass that rotates at the same time as the crankshaft. Thanks to its inertia, its function is to dampen small but non-negligible variations in engine speed due to explosions in the combustion chambers, a phenomenon further accentuated since the adoption of big-bang timing by all V4 manufacturers. in MotoGP.
Today, despite electronics, it has become a very sensitive area in order to have the best possible grip, whether when going around during acceleration, or in engine braking when decelerating. Too light, the flywheel makes the engine too brutal, with all the ensuing loss of grip. Too heavy, the latter becomes clumsy and not lively enough.
It therefore becomes extremely important not to make a mistake in the choice of this additional mass, and yet this is what Yamaha did in 2017 and Suzuki in 2018, one by adopting a flywheel that was too light, the other too heavy, without being able to react throughout the season since the engines are sealed for a full year.
Meanwhile, there was a good laugh among the V4 manufacturers, and in particular at Ducati where the near necessity of outsourcing the flywheel had been implemented for a long time, as evidenced for example by this photo of the GP12 by Valentino Rossi (before 2012, the smaller flywheel was hidden behind a protection, first in steel then in carbon).
Not only does this allow, in the event of an error, to correct the situation during the season, but above all to change this mass according to the needs specific to each route. We easily understand the advantage of such a system…
Today, at Ducati, we obviously still use an external flywheel, just as Aprilia is preparing to do.
At Honda, also in V4, no information has been released and no photos can really prove that such a system is used. However, according to our sources, this is indeed the case, the flywheel this time not being visible since it is mounted behind the alternator. This does not prevent it from being removable without breaking the seals, and therefore from being able to mount a different mass according to the needs of each layout.
There remains the KTM case where we have no information, but where it would be surprising if Mattighofen did not follow this already well-established trend...
Well, this is all very well, but does this mean that Yamaha and Suzuki are condemned indefinitely to suffer from a handicap compared to V4s?
A few snippets of conversation heard in the paddock lead us to think not: Yamaha in particular is reportedly studying such a system, despite the fact that it is much less easy to implement on an in-line 4-cylinder.
Of course, in theory, we could mount the flywheel at the end of the crankshaft, but this is not recommended either for the forces on the latter, nor for the dynamic behavior of the M1, nor even for the overall width of the assembly which could then compromise the maximum angle grip.
The ideal would therefore be to rotate this mass in the axis of the motorcycle, while remaining removable without breaking the seals which connect the crankcases-engine, cylinder head, etc.
However, there is still such a space available on the Iwata thruster: behind the cylinders, under the injection bodies, with the generator. For this, the flywheel, which does not need to be as large as for a V4, would therefore be driven by the following kinematic chain: crankshaft / intermediate shaft also serving as a balancer shaft and when starting the engine / clutch crown / generator and therefore flywheel.
There, well out of sight but in complete compliance with the regulations, the flywheel which could be changed depending on the circuits would fulfill its role perfectly and would thus make it possible to reduce to nothing one of the two handicaps experienced by the inline four cylinders for the last three years (the other being maximum power).
Needless to say, we are not ready to verify this possibility using photos!
On the other hand, forewarned is forearmed, it will be extremely interesting to observe the Yamahas and listen to the statements of the men with three tuning forks during this season...
