Engine air supply and exhaust systems

If all conditions were perfect the fuel and air would burn to produce carbon dioxide, superheated steam, and nitrogen (Fig. 4.1). Unfortunately these ‘perfect’ conditions are rarely achieved and significant amounts of other harmful gases, namely carbon monoxide CO, hydrocarbons HC, oxides of nitrogen NOx and solids (particulates like soot and tiny metallic particles) are produced (Fig. 4.2).