Abstract: A throttle valve positioned at either the inlet or outlet of an internal combustion engine aftercooler has the advantages of increased air charge temperature and lower air pressurization at low ambient air temperatures. The throttle valve reduces the effective aftercooler cross-sectional area available to transfer heat energy from the air charge to the atmosphere. The air velocity increase through the restricted aftercooler also decreases the heat transferred to the atmosphere. The air charge thus retains more heat energy in the form of higher intake air charge temperatures. The throttle valve also imposes a flow restriction to the aftercooler, causing an increased pressure differential across the aftercooler, which decreases the amount of pressure boost actually delivered to the engine cylinder to desirable pressure levels.