Im no expert here, but I think there are a lot of variables that affect the final smell of a diesel.
Of all the variables, I have noticed that timing seems to make a big difference.
I have had three diesels, GMC (6.2, Cummins, and Deere). All three have had their own smell and all three have had the smell changed when the timing was adjusted.
On a side note, Ive also noticed that temps seem to make a difference.
The smell on both my Deere and my Cummins change between a cold start and after a hard work out.
Just my thoughts.

 

^That makes sense because timing and temps all affect how the fuel is burned. With advanced timing a lot more NOx is produced, for example.

 

Nothin smells better than a 12-71 in the morning!!

Dave

 

I make and use my own biodiesel, and my exhaust used to smell like chinese food and candle-smoke. Then I did all the stuff in my sig, plus recently bumped my pump to the head. Now the exhaust smells like chinese food in a burning wax-paper bag. Awesome.
My father-in-law has an '05 Cummins Megacab and he used to bum bio from me. Even with B100, his truck's exhaust still smells bitter.