Flextube™ Catalyst Performance In 4-Stroke Motorcycle Exhaust Systems

An analysis of 4-stroke motorcycle emission systems indicates that a heat tube has the potential for meeting the regulatory standards if the location in the exhaust pipe matches the specific operating temperature requirements of the device. The location of a heat tube is determined by the diameter and shape of the exhaust pipe. Since the exhaust flowrate and temperature across the catalytic device determine its effectiveness, it is suggested that a flexible catalyzed tube, which could be placed anywhere in the exhaust, would have a greater potential than a rigid heat tube for solving a wide range of emission application needs. To maximize the benefit from such a simple, cost-effective device, application of the “flex-tube catalyst” was studied over a wide range of conditions.

A test matrix that used high and low levels of Pt/Rh ratio and tube diameter was used to study “flex-tube catalyst” performance in 4-stroke motorcycle exhaust systems. Engine variables include inlet temperature, AFR, exhaust flow and backpressure. Catalyst variables that were probed included tube diameter, precious metal ratio, and rigid or Flextube™ design. Data will be presented to show the benefits of such a device in various configurations. Performance is assessed by comparing the conversion of pollutants at various temperatures and flowrates.