The progect object is an exhaust system structure for the resolution of the problem how has the "biker" how wants to use his motorcycle on the race circuit and even on the road. The matter born cause the biker uses always a different exhaust system between circuit and road use. The reason why it is necessary have two exhausts, it is that the racing system is not able for road use cause it doesn't follow the European rules 97/24 CE against noise pollution. With our project we have realyzed an exhaust system how grants in few seconds to can transform an homologated system in a racing system, and allows to transform it again in an homologated silencer.