To most people, a car that is very economical in fuel consumption can’t be much fun to drive because it would probably be slow and perform uninspiringly. In some ways, this perception is based on the understanding that to get better fuel consumption, you have to drive at a lower speed and you would also need to use an engine with a small displacement that didn’t give out much power or torque.
But what if I told you that you can get a car that returns as much as 35 kms/litre (98.8 mpg) while driving normally and can get up to a top speed of 180 km/h as well as sprint from standstill to 100 km/h in less than 12 seconds? No way, you retort. Well, there is such as car and it’s no one-off prototype either. It’s the Honda Insight and over 5,500 units are running on roads in Japan, UK and North America (and two in Southeast Asia). Launched in Japan in November 1999, the Insight lays claim to being the world’s most fuel-efficient and environment-friendly car in volume production (at a rate of 20 – 30 cars a day).
In developing the Insight, Honda had the following objectives:
– To create the world’s most efficient production car, and to achieve extremely low emissions
– To make the car fun to drive
– To achieve the levels of safety and comfort that consumers expect
– To be able to sell this car at reasonable prices
However, an important consideration which was emphasized by the Insight’s Chief Engineer, Kazuhiko Tsunoda, was that the car had to really appeal to consumers. “It must be a real-world product for the global market,” he told his project team. This was crucial because of the experience with other environment-friendly models that Honda had developed earlier which did not sell well.
Although the Insight has advanced technology under the skin, it does not look very futuristic and resembles a 2nd generation Honda CR-X, except that the rear wheels are partially covered. Yet, the bodywork has the lowest drag coefficient (Cd) of any production car – 0.25! This incredibly low figure is the first of the various approaches taken towards enabling the Insight’s ultra-low fuel consumption and is an important area. Making the car more slippery means less resistance as it moves through the air, reducing the energy needed to move the car at a given speed.
Besides having all panels tightly fitting, attention was also given to making the underside of the car as smooth as possible to minimise drag-inducing turbulence and create a beneficial venturi effect. In the versions sold in UK and the USA, there is even a flat panel installed under the car to make it very smooth.
Apart fron wind resistance, weight also has an effect on fuel consumption so the Insight has been made as light as possible. At 820 kgs, it is 15% lighter than a Honda City (the chassis itself is 80 kgs lighter than a Civic’s) and the low weight comes from a combination of various measures but the major contributor is the extensive use of aluminium and plastic. Having gained much experience from producing the aluminium-bodied NSX supercar, Honda’s engineers were able to apply the knowledge to designing the Insight’s structure by using a variety of methods from extrusion to die-casting and sheet-forming. Though light in overall weight, the Insight’s structure actually registers bending and torsional rigidity that are, respectively, 13% and 38% better than the Civic’s.
Aluminium is also used for many components in the chassis to keep weight down. Even the front brake calipers are of aluminium and the cast aluminium wheels are 40% lighter than other aluminium wheels because of their special construction.
Aluminium may have one-third the weight of steel but it still offers very good resistance during an accident if the engineering is done well. In the case of the Insight, the floor construction provides the strong foundation that deforms minimally upon impact. Frames in the floor absorb and disperse the energy of front or rear impacts while impact forces on the sides are absorbed by the rigid side sills, cross-members and anti-intrusion beams inside the doors.
The whole concept of occupant protection is termed as ‘Honda G-Force Control Technology’ (which goes by the catchy acronym of G-CON) and includes such features as collapsible bonnet hinges and wiper pivots. It enables the Insight to pass in-house crash tests (which are tougher than US standards) that subject the car to a full frontal collision at 55 km/h, an offset frontal collision at 64 km/h and rear/side collisions at 50 km/h.
With its sporty looks, the Insight should rightly have nimble handling. However, in the interests of weight-saving, a simple layout has been used comprising MacPherson struts in front and a H-shaped torsion beam arrangement at the rear. The front suspension, with many lightweight aluminium parts, has an optimised roll-centre height and toe variation characteristics to enhance stability while the rear suspension, which has a compact layout to minimise intrusion into the boot, is designed to have a toe-in effect during cornering for more stable tracking.
The superior fuel consumption that the Insight is capable of is not just due to the Integrated Motor Assist (IMA) powerplant. The IMA contributes 65% (35% from the petrol engine, 30% from the electric motor assist) while the aerodynamics and ultra-lightweight body contribute 35%. To read more about the IMA technology, click on this link.