The warm up three way catalytic converter (WU-TWC) and the under-floor three way catalytic converter (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.
The WU-TWC is attached directly under the cylinder head that is integrated into the exhaust manifold.