Most of what we're seeing is condensing steam not smoke. The Chinese engines tend to run with clear stacks, which is why so many of us go in the cold of winter to get the "smoke" effects caused by condensing exhaust steam. Also the drivers don't work these engines all that hard, because they are relatively slippery. Hans Schaeffer, on his web sight, has a detailed description of how the Chinese drivers run the QJ's over Jingpeng, see the link below. It would be interesting to hear one of the experienced C&TS hogheads compare driving a QJ over Jingpeng with taking a full tonnage passenger train up Cumbres during the Fall "stock rush". My sense is the C&TS engines are forced to work a lot harder.
John West