Don’t think we just need fins on Engine components to take of all the heat from the Engine. We have to learn how to direct the air flow in such a way to get high efficiency in heat dissipation which we will discuss in this post. Before getting into it let me introduce you some terminology so you would understand it better.
Streamlining: Design or provide with a form that presents very little resistance to a flow of air or water ( increasing speed and ease of moment ).
Cowling: A streamlined metal housing or removable covering for an engine.
Duct: Any tube, canal, pipe or conduit by which a fluid, air or other substance is conducted or conveyed.
Duct work: A system of ducts used for a particular purpose as in a heating system or ventilation.
When the vehicle moves with certain velocity there will be a enough moment for air to transfer heat. We know that fins on the air cooled engine increase heat transfer rate. For the better moment of air around the Engine we will improve streamlining which requires a small frontal area demanding narrower Engine. For narrow Engine, cylinders have to be placed behind each other which demand duct work ( cowling ) to make sure enough air flow to the rear cylinders of the engine. The shape of the cowling directs the air current ( forced convection ) around all the cylinders and also provides a direct exist after the air has extracted and absorbed the heat from the Engine. FLAT FOUR-CYLINDER ENGINE ( wish you have better knowledge about types of Engine ) employs Baffles ( are flow-directing or obstructing vanes or panels ) to improve air distribution between cylinders and to direct additional air to critical components such as oil cooler.