Ducati not so long ago unleiled a set of Akrapovic exhausts on their WSB factory bikes that were radically different from the already unique set-up of the road bike.
Their two silencers under the sump that put gases out down and away from the motorcycle changed to two silencers in the same location, but only one of these was a silencer in the conventional sense. The other one exited higher up and behind the rider's right foot. They cost a fortune – each set over 10,000 Euro (around 340,000 THB) – but that was not the bone of contention for some.
A few rivals said that Ducati broke the rules of the class, in that the racebike pope design has to follow the same geometry as the roadbike. So it the roadbike has one pipe on the left and one on the right, you have to follow that rule. But as each silencer on the Ducati exits on the same side as the original, and given that the design can be changed, that is enough for the rules. Many WSB machines change the look and even location of the exhaust system on the roadbike, but are still perfectly legal. Honda's roadbike exhaust exits low and to the right while their racebike on exits high – but crucially, to the right.
Kawasaki has a power valve inside the pipe and also links different cylinders to different exhaust outlets compared to the roadbike. But it does still exit on the right.
In general, fewer balancing pipes are present compared to previous seasons.
With a reduction in top-end tuning and many standard parts inside the engine due to the 2015 rules, exhausts needs have changed, from chasing top revs to beefing out the midrange as well. Midrange is a relative term, as nobody is asking their motorcycles in WSK to drop below probably 7,000rpm or so when riding in anger on the track.
Decibel limits under the rules are 107dB, after the race – noisy, but not anti-socially so.