A method for controlling exhaust gas temperature or space velocity

A method for controlling the temperature and/or space velocity of exhaust gas to control the maximum temperature of the exhaust gas to prevent thermal damage to the Diesel engine components and associated aftertreatment devices during regeneration of the aftertreatment devices. The method includes controlling intake and/or exhaust valve opening timing and duration, either singly or in combination with selective individual cylinder cutout, in response to sensed engine operating parameters.