does the outlet diamiter of a silencer have to be equal,or larer than the inlet or can it be smaller? i am wanting to fit a bike race silencer to a CEC. the 4-2-1 exhaust has a 3" outlet. i wanted to modify a bike silencer to take the 3" pipe but it has a 2" outlet?

Some engine actually like having a bit of back pressure in the exhaust, (Cossy V6 being one). But if your engine is turbo'd then its a definate No No as you will restrict the gas flow. HTH Ray