Abstract: A combustion unit (15) is primarily intended to feed a turbocharger (18) to generate a compressed air supply to an internal combustion engine (10). The unit (15) is supplied with exhaust gases from the engine and these gases are mixed with air in the unit combust material in the exhaust gases and give and enhanced supply to the turbocharger. The combustion unit is generally cylindrical and air is added to the exhaust gases at the inlet (13) to promote combustion and the combustion gases pass at high speed through an annuler space towards an outlet (17) leading to the turbocharger (18).