Kobayashi, T., Kosei, K., Ito, S., and Iijima, S., "Effect of Variable Cooling System for Fuel Economy Improvement on Scooter with Air Cooled Engine," SAE Technical Paper 2016-32-0092, 2016, doi:10.4271/2016-32-0092.
A variable cooling system has been developed for scooters equipped with an air cooled, four-stroke, single cylinder gasoline engine. This system opens or closes louver located at the cooling air inlet using an oil-temperature sensitive actuator. When the engine is cold or the engine load is low, the louver shut off the cooling air for a quick warm-up and for maintaining the engine oil temperature high to reduce the friction losses that occur with low oil temperature while eliminating the loss from driving the cooling fan as well. The quick warm-up also decreases supplementary fuel injections necessary when the engine is cold. Consequently, fuel economy improvement by 3.3% was realized in running condition of the Urban Driving Cycle.