The locomotives at Saint Patch Grade, that means the SD40-2, GP38-2, ES4400AC, created clearly visible exhaust when the engine was running. In my opinion this exhaust rather looks like steam so I always get the impression that the engine must be broken and burns its coolant. The exhaust should look less white, more grey and more translucent than the present white "clouds". But after all, the CSX locomotives have exhaust! But when I'm driving on a Class 66, Class 166, or Class 43 I absolutely cannot see any exhaust. I know that the locomotives have to meet very hard emission norms, which might be a reason why there is not as much exhaust visible as on the CSX locomotives. But especially the HST, build in the 1970s, when emission laws were less strict, should produce visible exhaust. The Classes 166 and 66 were build in later years, but nevertheless I cannot imagine that there is absolutely nothing coming out of the exhaust pipe. At least some flickering air should be visible.
Smoke needs some work regardless. Now it's not really wispy or cloudy enough, so it looks too thick and too much like a 'stream' of smoke rather than a cloud. You look at these in real life and do not see that arc of smoke coming out, usually a thick bit of a stream right at the stack that quickly spreads out into a thin wispy cloud. One thing that would probably help the effect is if smoke emission speed with engine power; so at higher power smoke would be coming out of the stack more violently-as now it always comes out at the same, pretty lazy pace, which makes high power not feel so powerful. Also, if smoke were influenced by wind, that would be nice, but most scenarios and weather presets have wind foolishly set to 0, so few people would ever see that. (For inspiration of what good smoke would do, look at Thompson's Class 37/4 in the West Highland Line Extension route for TS2017. That one machine's smoke always impresses me.)
