The beauty in fuel efficient car technologies

Many car buyers who are cautious about fuel consumption go with one metric to the market, be it the Internet or the car bond, engine size. With a smaller engine there is less fuel consumed.

Thursday August 7 2014

My Car clinic participants learn how the engine

My Car clinic participants learn how the engine works. Newer cars have advanced engine technology. PHOTO BY ABUBAKER LUBOWA 

By Mustafa Ziraba

Many car buyers who are cautious about fuel consumption go with one metric to the market, be it the Internet or the car bond, engine size. With a smaller engine there is less fuel consumed.

What they do not realise is that depending on one’s primary car use, other variables come into play and the “smaller engine less fuel” adage does not hold anymore. But, with the sustained high prices of fuel, buying a fuel efficient car is a way to save money. Car manufacturers know this and the car engineers are always on the edge trying to squeeze an extra kilometre out of that litre.

How do they actually do this?
Increasing fuel efficiency of a car in the most basic sense rotates around having the car work less to achieve the same thus less fuel or you get more out of the same fuel.

Categorically, these ways include finding ways of reducing wind drag by way of exterior design. This is usually stated in terms of the car’s drag co-efficient. This is what engine technologies manufacturers employ to increase the overall efficiency of the engine. The third is an attempt to reduce friction generated by the car’s moving parts. Finally, simply reducing weight by use of lighter materials such as increased use of plastics.

While it is nice to hand over a list of the most fuel efficient cars on the market today, it is also important to understand what makes a car more efficient than the next car. The newer cars we are seeing today do utilise multiple technologies to increase the mileage. Let’s have a look at technologies some of you perhaps have come across.

Variable valve timing with intelligence is popularly known as VVT-i by Toyota, or i-VTEC by Honda. This is a technology that automatically controls the timing of the engine’s inlet and exhaust valves to ensure that whatever the driving conditions, stop start traffic or highways the engine works to maximum efficiency. As an engine’s speed increases, the optimal setting for valve lift and timing changes. Traditional engine designs use fixed timing settings that are a compromise between low and high speeds.

Superchargers and turbochargers are pumps that force air into an engine’s cylinders. Superchargers are powered by the engine itself, while turbochargers are powered by the car’s exhaust. Of course with more air, there is more fuel so how does it work? First off compressed air is ripper for complete combustion so when engaged you get a power surge giving you more bang for your fuel. Then many manufacturers are fixing super and turbo chargers to relatively small engines.

As such, most of the time when you have not floored the pedal you are rocking the small engine size. When you do floor the pedal, then the supercharger or turbo kicks in. I have to qualify this by saying if you drive aggressively, which is almost always the case for many bigger super charged cars, you shall see a significantly lower fuel mileage.

While found mostly in higher end luxury cars, this to me is so simple yet the coolest. Also known as displacement on demand, multiple displacement, and variable cylinder management, this engine technology increases fuel efficiency by deactivating some of the car’s cylinders when they are not needed. For example, when a car reaches a steady highway speed, one or more of the engine’s cylinders is disabled. Deactivation can be used on six and eight-cylinder engines, and still maintain an engine’s smoothness.

There are several subtle innovations around the materials used, light weight construction, engine designs including the shape and materials used, all aimed at squeezing that extra kilometre out of your car. While some technologies give significant benefits, others give benefits on paper and not necessarily in the real work where many other variables such as age of car, fuel quality, etc, come into play.

Unfortunately though, the test-bed of newer advanced fuel saving technologies is in the luxury and high performance segments, drivers of more modestly priced cars eventually benefit as technology and expertise trickles down in later years.