The next time you see a semi truck rumbling down the highway, pay attention to the vertical exhaust stacks rising up from behind the cab. These exhaust pipes aren't just for aesthetic purposes ...

Semi trucks are heavy pieces of machinery, and using the regular brakes might not be enough. You might need the help of the jake brake or the retarder.

We got a chance to see the truck at Irwindale Speedway ... The wastegate pipes are bundled together with a large stainless steel exhaust pipe attached directly to the turbo. After the engine ...

Southern California truck spotters will have plenty of electric ... and diesel particulate emissions coming out of their exhaust pipes.