Automobile Engineering in ME
A three way catalytic converter

Reduces N₂, H₂O, and CO₂ emission levels
Removes CO, HC, and NO₂ from the exhaust gases passing through it
Re-circulates exhaust gases
Burns fuel vapour gases

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Automobile Engineering in ME
The function of a second ring is that it is a

Back up compression ring which will work in place of the top ring when it is broken
Cushion ring which prevents piston slap and knock
Back up oil control ring which will work in place of the bottom ring when it is broken
Compression ring and aids the top ring in sealing and cooling

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