Patent ID: 7325651
Filing Date: 2008-02-05
Classification: F01N

Abstract:
1. A motorcycle exhaust system, which comprises: a motorcycle combustion engine mounted on a motorcycle frame structure at a location generally intermediate between front and rear wheels; an exhaust passage fluidly connected at one end with an exhaust port of the motorcycle combustion engine; a silencer disposed at the opposite end of the exhaust passage and supported by the motorcycle frame structure at a location generally above the rear wheel and having a plurality of expansion chambers including a first expansion chamber defined upstream in the silencer with respect to a direction of a flow of an exhaust gas and a second expansion chamber defined downstream in the silencer with respect to the direction of the flow of the exhaust gas; a first connecting passage communicating between the first and second expansion chambers; an exhaust control valve disposed in an inlet of the silencer for variably adjusting the sectional area of the exhaust passage and being disposed forwardly of an inlet of the first connecting passage so as to face towards the inlet of the first connecting passage; a throttle valve; and a valve controller for controlling the exhaust control valve in dependence on at least the number of revolutions of the motorcycle combustion engine and the opening of the throttle valve; wherein the inlet portion of the silencer is formed by a silencer inlet pipe and the first connecting passage is formed by a first pipe, wherein an outlet of the silencer inlet pipe and an inlet of the first pipe forming the inlet of the first connecting passage occupy respective positions separate to each other within the first expansion chamber, and wherein the valve controller controls the exhaust control valve to be set to a substantially closed position during a low speed operating condition so as to lead a major portion of the exhaust gas into the second expansion chamber through the first pipe at a high velocity without expanding within the first expansion chamber, and to be set to the full open position during a high speed operating condition so as to lead a major portion of the exhaust gas into the first expansion chamber at a low velocity.