In accordance with one embodiment, the present techniques relate to a ground power unit that supplies electricity to an aircraft. The ground power unit may include a generator coupled to a diesel piston engine. A turbocharger may pre-compress the air consumed by the diesel engine, and a charge air cooler may cool this air before it is introduced to the diesel engine. The charge air cooler may be placed upstream from the diesel engine in a primary air flow. Advantageously, drawing air through the charge air cooler that has not first passed over the engine may lower the operating temperature of the ground power unit.