Warm Up Three Way Catalytic Converter (WU-TWC) and Under-Floor Three Way Catalytic Converter (Under-floor TWC)

The WU-TWC and the under-floor TWC convert hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) in the exhaust gas to carbon dioxide (CO₂ ), nitrogen (N₂ ), and water vapor.

WU-TWC (ATTACHED TO THE CYLINDER HEAD) 

Fig 1: Identifying Catalytic Converter System - WU-TWC (Attached To Cylinder Head)

Courtesy of AMERICAN HONDA MOTOR CO., INC.

UNDER-FLOOR TWC 

Fig 2: Identifying Catalytic Converter System - Under-Floor TWC

Courtesy of AMERICAN HONDA MOTOR CO., INC.