If you’ve ever put your hand out the window of a moving car, you’ve experienced aerodynamics. Put your hand flat and the air slips by, but if you hold it up, the wind pushes it.
Much of the fuel your vehicle burns is just for overcoming this resistance; GM is helping to reduce this with an innovative new air shutter on the new Chevrolet Cruze sedan.
Made of high-strength plastic and tucked behind the grille for protection from road debris, the shutters open and close similarly to a Venetian blind, says Greg Fadler, aerodynamics engineering group manager for GM North America.
“There is a five per cent improvement in aerodynamic drag,” Fadler says. “That’s huge, because the horsepower required to overcome aerodynamic drag goes up with the cube of vehicle speed. It takes 50 per cent more horsepower to go (128 km/h) versus (112 km/hr). Above (72 km/h), aerodynamic drag is the largest drag on the vehicle. What we’re doing is reducing the number-one draw on fuel consumption.”
The system will debut on the Cruze Eco, a special fuel-efficient trim level, but will eventually be rolled out across numerous GM products. In effect, they change the shape of the front end, allowing the car to “cut through” the air more efficiently.
The system uses a number of sensors that determine factors such as vehicle speed, and the temperature of the engine and outside air. Since they block off the radiator, used to cool the engine, they stay open when maximum airflow is required to reduce engine temperature, and close at higher speeds to reduce wind drag.
“It’s designed so that it doesn’t have to open in freezing conditions,” Fadler says. “The cold air provides that extra cooling capacity.” This eliminates any danger of the system trying to open shutters that are frozen shut.
“We tested the performance to the level of having all your luggage and your family loaded in on vacation in Death Valley, and it’s (43C) outside, and your air conditioning and cooling system are working at maximum capacity to keep you comfortable and the engine in the normal temperature range,” Fadler says. “But if it’s a fall day in Toronto, and the temperature is maybe (10C), you need far less air in that scenario, so the system shuts down that excess capacity when it’s not needed.”