btDynamicsWorld::stepSimulation (...
I was eagerly moving forward into the dynamics of my character control, but I had to back up and debug some issues first.  Was getting some serious jittering in the rendering of my playerCube and the btRigidBody was lagging behind the render.  Also I was easily escaping the level at high speeds. Realized I needed to increase the resolution of my physics simulation.  I was getting quite a kick out of frame rates near 2000, but after forcing a smaller timeStep, the issues cleared right up : ) But now my frame rates are around 120 : [ 
Also added an irr::io::IWriteFile for logging debug info