April 6, 2011
2011 Chevrolet Cruze Eco. Click image to enlarge
By Jim Kerr; photo courtesy GM Canada
The December, 1917 issue of Popular Science describes an automatic shutter system for automobiles: its purpose was to maintain a constant engine temperature by opening and closing shutters to vary airflow over the radiator. John Deere used them on the 1930’s Model D tractor we had on our farm. Highway tractor trucks have used them for decades, and some large stationary engines used shutters to regulate engine temperature. I have even seen aftermarket automotive units in antique magazines that worked like a simple roller blind – pull it down to block the air flow, and let it roll back up when you need more cooling.
Now, modern cars are getting air shutter systems too. Within the last year, the Chevrolet Cruze, the Hyundai Sonata and the new Ford Focus have added shutter systems on specific models. Although the concept is the same as on those antique vehicles and large trucks, the shutters have an additional purpose. In these new cars, the shutters are there to increase fuel economy, too.
With the United States average fuel economy standards rising to 50 mpg U.S. by 2025, auto manufacturers are looking at every method to increase fuel economy: low rolling-resistance tires, close-out panels beneath the body to reduce drag, aerodynamic spoilers and outside mirrors, and even turning the charging system off when the battery has a sufficient charge are some of the current fuel saving techniques used on many new vehicles.
Now we can add air shutters. The air shutters on all three of the above-mentioned cars are like a plastic venetian blind behind the grille. The engine computer monitors parameters such as engine and transmission temperatures, vehicle speed, outside air temperature, air conditioning and cooling fan operation and vehicle load to determine when the shutters should be open or closed. A small electric motor operates the shutters.
Today’s vehicles are designed to operate at extreme temperatures. Few of us will cross Death Valley in the heat of the day, but some of us may pull a heavy trailer up a steep mountain grade. Vehicle cooling systems are built big enough to handle the cooling loads for extremes, but in order to do that they need airflow through the radiator. The vehicle grille air intakes and radiators have to be large enough to supply that cooling.
Most of the time, this maximum cooling capacity isn’t needed and that is where the shutter systems help; with the shutters closed, airflow is restricted to the radiator and engine compartment. This does a couple things. First, air now moves around the front of the vehicle. Second, the air doesn’t enter the engine compartment so it doesn’t have to exit beneath the car. Both of these make the car more aerodynamic, which improves economy.
How much does it help? On the Chevrolet Cruze, GM says it will decrease fuel consumption 0.2 litres per hundred kilometres, a drop in fuel use from 4.8 L/100 km to 4.6 L/100 km, which is equal to half a mile per gallon combined, city/highway. That may not seem like a lot, but that is a savings of 40 litres of fuel every 20,000 km, about the average yearly distance a car is driven. Multiply that by the mileage a vehicle is driven during its lifecycle and the number of vehicles on the road and you can see it quickly adds up to significant amount of fuel saved.
For those of use who aren’t driving these new vehicles, there are always grille covers available from the aftermarket, or if you want to go cheap, cardboard stuffed in front of the radiator will work somewhat. Of course, these methods rely on the driver manually changing things when temperatures and driving conditions change. Forget and you could overheat your engine; the automatic systems are much better.
Finally, while the manufacturers are incorporating new features to improve economy, driving habits still make the biggest different. Drive for economy and it can save you big bucks at the gas pumps.
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