The Econodyne was a great step forward accomplished when Mack brought out the first charge air cooler located in front of the radiator. Prior to this development, engineers had not yet figured out how to have the air travel that far from the turbocharger compressor outlet, through a large heat exchanger, and back to the intake manifold without excessive pressure loss. Volvo claims to have beaten Mack to the punch with this concept about a year before, but Mack was the first US manufacturer to do it. Cooling the intake air after allowing the turbo to more than double its pressure improves fuel economy because cool air is easier to compress and produces less waste heat in the cylinder, while the high pressure and moderate temperature greatly reduces particulate and NOx (improves combustion). The concept was introduced in Hagerstown and I still have a commemorative model truck from the event, which occurred in about 1981.
