Regarding the S3, I experienced a Homer Simpson DOH!! I took a look at the S3 parts breakdown on the Lionel website and saw that it has a dual smoke unit similar to the one on the Big Boy. One unit for the stack and one for cylinder steam.
However there is only the single stack for feeding the units. Out of the stack there is one funnel that has 2 separate spigots for feeding each smoke unit. That means when dosing the loco, your dose is split into 2 channels - 1/2 dose to each unit. Out of the box, the cylinder steam activates automatically. Probably not a good idea to shut it off and thus over saturate its smoke unit when you add fluid to replenish stack smoke. Why care??? keep in mind that I am the grim reaper of smoke units.
