please explain to my stupid head
Joined: Dec 2003
Posts: 6,598
Likes: 10
From: Temple, Texas (Central)
It helps emissions by diluting the exhaust gases with fresh air, providing fresh air to help the cats clean the exhaust, plus it keeps the cats from burning up.
The main thing gained is a less cluttered engine bay. On an s4 you might gain a few hp, nothing very noticable. On an s5 NA, you would lose a lot of top end because it operates the aux ports and vdi.
The main thing gained is a less cluttered engine bay. On an s4 you might gain a few hp, nothing very noticable. On an s5 NA, you would lose a lot of top end because it operates the aux ports and vdi.
Former Moderator. RIP Icemark.
Joined: Apr 2001
Posts: 25,896
Likes: 24
From: Rohnert Park CA
Monolithic cats (3 way cats- ones with air pump inputs) need the air to be pumped in to complete the process of breaking down the unburnt Hydrocarbons in the exhaust.
Think of the Monolithic cat as two different cats in one case. One part cracks the hydrocarbons into carbon monoxide and the 2nd part changes the cracked mixture to CO2 and H2O.
Without the air to help complete the process, the cat can clog, and then in the case of a rotary motor, melt down internally.
It has nothing to do with dilution, but rather the O2 is used to help the last stage of the cat break down the remaining unburnt hydrocarbons and Carbon Monoxide.
Think of the Monolithic cat as two different cats in one case. One part cracks the hydrocarbons into carbon monoxide and the 2nd part changes the cracked mixture to CO2 and H2O.
Without the air to help complete the process, the cat can clog, and then in the case of a rotary motor, melt down internally.
It has nothing to do with dilution, but rather the O2 is used to help the last stage of the cat break down the remaining unburnt hydrocarbons and Carbon Monoxide.
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