I've noticed on many GM diesel trucks a device that I interpret to be some sort of exhaust extractor. It is a section of tubing, approximately 1 1/2 " larger in dia than the tail pipe, welded on to the end of the tail pipe with S-shaped pieces of round bar. It looks like there is a section of the larger tubing that is necked down like a venturi positioned just beyond the end of the tail pipe. I've seen them installed on private vehicles, business vehicles, and even public transportation vehicles. I'm just wondering what the heck it's called, what it's supposed to do, and why don't I see it employed on anything else besides GMs. Inquiring minds want to know!Thanks for your time,Joe in St Louis

I think you are talking about the difuser on the newer diesels with Diesel particulate filter systems. When it goes through a regen cycle to clean out the DPF the exhaust is super hot and the design pulls in extra air to cool the exiting exhaust gasses for safety reason.

I've seen that too and agree it must be for cooling the exhaust gases and piping during regen. I imagine the piping could get hot enough to hurt someone if they bumped against it even though regen is only supposed to happen at highway speeds.

Even the dodge FSM states that the exhaust gases have to be at least 1,000*F for regen effect to happen for the DPF...

Looks like this.

They wouldn't be so bad IF the manufacturers would hide them under the box better. I think they look like crap.