Exhaust System: Notes

The purpose of the exhaust system is to convey engine emissions from the exhaust manifold to the atmosphere. Engine exhaust emissions are directed from the engine exhaust manifold to the catalytic converter through the front exhaust pipe. An HO2S is mounted on the front exhaust pipe before the catalyst. The catalytic converter reduces the concentration of carbon monoxide (CO), unburned hydrocarbons (HCs) and oxides of nitrogen (NO ^x ) in the exhaust emissions to an acceptable level. The reduced exhaust emissions are directed from the catalytic converter through another HO2S mounted in the rear exhaust pipe (Fig 1) and then on into the muffler. Lastly, the exhaust emissions are directed to the atmosphere through an exhaust tailpipe.

Note on some Partial Zero Emission Vehicles (PZEV), there will be a total of 3 HO2S in the exhaust stream. One near the exhaust manifold (stream 1), one in the middle of the light-off catalyst (stream 2) and the third (stream 3) is mounted after the light-off catalyst (Fig 2).