Cat Back Exhausts

[Squark]

Wow, thats a very interesting thread about the scooby,
a long read but very interesting indeed

 

[Hate]

Diff cars have diff tests. My 1994 car doesnt need a cat.

But thats cause its an import and the engine was never released in the UK.

in the celica it was

 

[Dogbreath]

Actually it's usually the other way around, especially on forced asperation cars (on NA cars the exhaust is seldom the restriction at all). Look at it this way: on its way out of the engine the exhaust gas is at its hottest (about 8-900oC) and thus occupies the most volume for a given weight of gas. It therefore needs the maximum diameter pipe to escape through.

That's massively over-simplified, having a huge diameter pipe will actualy cause power loss. The aim is to keep the gas velocity as high as possible whilst causing the minimum back pressure.