Sorry, but you've gotten it wrong.
Diesel engines do smoke from any number of reasons; turbo clutch problems at the front of the pack with EMD prime movers (unique in that they are actually a hybrid. A two stroke engine, the turbo is gear driven through notch five and in notches six, seven and eight it runs as a true turbocharger, hence the need for the automatic turbo clutch. GE prime movers are a four stroke engine with a true turbocharger, an engine of ALCO origin, which is why they sound so different) but it can be due to bad rings and/or improper injector rack settings, fuel filter system problems or other anomalies, such as with governor oil shortage, air filter intake or problems with the inertial filters.
On older diesels that have roots blowers instead of turbochargers, the problem can be from the carbon trap caps being plugged up. Very bad news as fire out the stack and cinders ejected can start forest fires. These days they are usually found only on heritage 'tourist' railroads.
The actual riddle is, an 'electric engine' is traveling etc.. etc. etc., which way does the smoke blow...
But for the question asked locomotives always run away from the smoke they create, so the perception will be the smoke coming from the south. If you're running at 45 mph it is going to take at least 50 mph tail winds for it to be different.
I get lucky from time to time when my three remaining brain cells sync up...