|
Rangers have two fans: 1) A mechanical fan with a temperature dependent viscous fluid clutch, and 2) An electric fan. The electric fan only comes on when the air conditioning is on or extremely hot temperatures. The mechanical fan runs all the time, but the clutch has a lot of slip at low temperatures, causing it to run slower. As the temperature increases, the clutch fluid gets thicker, causing more coupling to the fan and the fan runs faster.
After I blocked the upper grill of my Ranger, it appears I picked up about 1 mpg for local driving. I haven't done any real highway driving since I blocked the grill in May to see if my highway FE is any better. The engine temp, per Scangauge, has dropped from a typical 210 in the summer to about 204 since blocking the grill. A drop in temp would indicate that the fan is running faster. But the fan speed is temperature dependent and a lower temp should be a slower fan speed. The fuel economy has improved, indicating that if the fan is working harder, the aerodynamic improvement is more than offsetting the fan's power draw.
|