The exhaust gas which is expelled from the combustion chamber in the fourth stroke is forced out of the engine through the cylinder head and the exhaust manifold. When it leaves the combustion chambers, the discharged gas still contains valuable energy. It is the task of the exhaust gas turbocharger to recover this energy.
Engines that are not supercharged—naturally aspirated engines—draw combustion air in because the pistons create a vacuum as they move back, and the air is drawn into the combustion chambers. The amount of air that enters the cylinders this way is limited. In order to draw more air into the combustion chamber, a turbocharger is used.
