Air- Or Water-Cooling: Exhaust Emissions, Consumption, Operational Response 785026

Approximately 10 years ago, air- and water-cooled engines held approximately equal portions of motor vehicle production. This investigation compared these two types in terms of emissions, fuel consumption, and operation.

The greatest thermodynamic difference between the two types is the amount of heat conducted away by the intended cooling medium; water removes twice as much heat as does air in their respective engines, with the balance of heat removal being born by exhaust and oil. However, tests show no difference in efficiencies between the two, although some sources have speculated that higher air-cooled engine-compartment temperatures would permit higher air/fuel ratios through improved carburetion. However, these higher temperatures do require greater engine component quality. Expected tendencies in exhaust and emissions failed to appear during tests, however, even during start and warm-up operation.

Choice of cooling depends on noise levels, engine compartment temperatures, and costs of development and production, but especially on water-cooled engines' greater capacity for temperature control. These factors have led to a present market share for air-cooled engines of less than 10%