I'm sure many of you are tired by now of being bombarded by Stinky Diesel Talk (stinky in more than one way).
But here's something to consider.
We are routed straight back at about 16" off the ground, rear exit with a 4" tube.
When in the LSR staging lanes, there were a lot of complaints, especially when cold, that the air behind our truck was obnoxious/unbreathable. But unlike many other engines, ours makes more power hot than it does cold, nor will it make much heat at idle. We have to keep it running in lanes.
In Sled Pulling, and some other forms of diesel competition, straight back exhaust is forbidden, but not because it smells nasty and chokes you.
A major area of concern is "spitting the wheel". It is normal for many diesel builds to overspeed the turbocharger. Why? There really aren't too many turbos designed to make 50+ PSI of boost within the factory map or shaft RPM. I monitor the shaft RPM with the help of Garrett, and I stay under the RPM limit, but that is not really typical.
When you overspeed, you can break the main shaft, and the turbine wheel can exit at very high speeds out the exhaust. These wheels can be nearly the size of your fist and be 1800 deg F. They have caused injuries in the past. So they make them run "cross-bolts" in the exhaust (Casper has these), and make us run the exhaust straight up, or aimed away from the crowds.
For the diesel entries, it might actually be safer and more "racer-friendly" to require (or just permit) upward facing exhaust, be it in the hood, or in the bed, which are the normal locations for racing.
Just a thought. I certainly don't want to change my truck, I like it the way it is, but it might be more logical to outlaw my style of exhaust.