Designed for higher fuel economy
Improving vehicles’ fuel economy is one of the foremost criteria facing vehicle manufacturers, not only because it is a competitive advantage, but also because of regulatory mandates implemented to make vehicular transportation less hazardous to the environment. The “green” advantages of fuel economy are now more in focus than ever before.
To achieve higher fuel economy, no stone is left unturned and even factors that may contribute even minimally are being researched and implemented. It is well known that the fuel consumption of a moving vehicle is related, in a major way, to aerodynamic drag of the vehicle, expressed as the drag coefficient, Cd. As the aerodynamic drag experienced by a vehicle increases, fuel costs also correspondingly increase due to the greater energy required to overcome the drag.
For example, a vehicle travelling at highway speed, uses a significant portion of the total fuel consumption to overcome aerodynamic drag. Thus, even a slight reduction in aerodynamic drag coefficient of the vehicle can result in some improvement in fuel economy. Reducing aerodynamic drag alone can provide a 10 per cent to 15 per cent fuel economy improvement for vehicles with a large faceprint, such as a tractor-trailer combination.
Unlike automobiles, these vehicles have a relatively high ground clearance and a large wheel assembly exposed to the impinging airflow. Thus the need for reducing aerodynamic drag of wheeled vehicles, traveling at highway speed, is compelling and widely recognized, resulting in use of flaps that close off air inlets, intakes that guide wind around wheel wells, spoilers that mitigate lift and reduce drag – just to mention a few.
Technology for fuel conservation in automobiles has evolved significantly and vehicle makers adopt several methods to achieve target. The US Department of Energy has listed the following steps vehicle manufacturers focus on.
Cylinder Deactivation is one such method. It is also called multiple displacement, displacement on demand, active fuel management, and variable cylinder management. This technology deactivates some of the engine’s cylinders when they are not needed. This temporarily turns an 8- or 6-cylinder engine into a 4- or 3-cylinder engine, saving fuel.
By Louis Rumao
(Full text in PTA Dec-Jan issue)