VanHonda

Well I remember reading on here before that the difference between a cast drag or rev-hard style manifold vs. a tubular Full Race style is the manner in which they spin the turbine. The cast style using the thermal energy and the tubular using the flow of the exhaust gasses. I was thinking about it in class today and I was wondering if anyone could explain more in depth about how the cast manifolds use the thermal energy rather than flow.
Thanks,
Craig