Tech - The old motor roars back

SMALL cars sometimes struggle to climb steep hills. But a converted Chevrolet Lacetti has something special to help it along. Instead of having to keep changing down and revving harder to ascend a winding Alpine-type test track, the engine can cruise almost to the summit in top gear. This is because the car benefits from one of the developments that in these more economical and greener times promises to give the petrol engine a new lease of life.
Old technologies have a habit of fighting back when new ones come along. This is not surprising because they often have an enormous amount of design, engineering and production knowledge invested in them—especially so in the case of car engines. So new hybrid systems, fuel cells and electric motors will be chasing a moving target. The internal combustion engine will be getting better too.
The Lacetti is just one example. It gets its extra oomph from a supercharger forcing more air into the combustion chambers of its engine. This is an old idea that used to speed up 1920s racing cars, like “blower” Bentleys. But their engines tended not to last very long. With stronger engines, superchargers have been staging a comeback in big cars. The one in the Lacetti is different: it is a dual-speed supercharger that provides its highest boost at low speeds. This gives the car a huge 40% increase in torque, or pulling power.
The car was fitted with the device by its developer, Antonov Automotive Technologies, a British company. The supercharger is purely mechanical and uses planetary gears to change speed. Antonov reckons that it could be used to reduce the size of a car’s engine by up to 50%—so it would use less fuel and produce fewer CO2 emissions, but still provide good performance.
Car engines (racing cars aside) have long been a compromise between efficiency, power and durability. Greater flexibility has come with fuel injectors, which can metre fuel more precisely than carburettors, and variable-valve control, which can optimise the opening and closing of inlet and exhaust valves to produce more power when accelerating or greater economy when dawdling around town. The same systems are also used in some big and thirsty V8 and V6 engines to shut down a few cylinders when driving slowly.
Now engineers are taking these developments much further. The e-Valve system developed by Valeo, a French automotive supplier, uses electromagnetic controls to open and shut valves instead of pushrods operated by a camshaft. As each valve can be operated independent of any other, all sorts of tricks become possible, including shutting down cylinders and switching temporarily from the traditional four-stroke Otto cycle (as developed by Nicolaus Otto, a German engineer in 1876) to a type of Atkinson cycle (an ultra-lean system invented as a rival in 1882 by James Atkinson, a British engineer, but which suffered from a lack of power). The Toyota Prius already uses a form of Atkinson cycle for the petrol engine that operates alongside an electric motor in its hybrid system.
Valeo reckons that on average their e-Valve system can cut fuel consumption and CO2 emissions in a car by up to 20%. It could also be used to make three- and two-cylinder engines that run efficiently and smoothly. These tiny engines could power small cars directly, combine with electric motors in hybrids or work as “get-you-home” engines or range-extending generators in plug-in electric cars.
Two-pot power
Fiat is investing heavily in smaller engines with its new valve-control system, Multiair. This uses hydraulics and electronics to optimise valve settings. When combined with a turbocharger (a supercharger driven by exhaust gases), Fiat engineers talk of producing a “downsized” two-cylinder engine that performs like a bigger four-cylinder one, but with fuel savings of some 20%. Fiat is expected to start using Multiair engines in its cars in a year or so.
Using a combination of variable valve-control, fuel injection and turbocharging, Daimler is developing an entirely new type of engine. It can switch between operating as a petrol engine, with agility and power, to operating as a diesel, with economy and torque. The DiesOtto engine, as Daimler has called it, starts as a petrol engine with spark plugs igniting the mixture of fuel and air in its cylinders, and remains as a petrol engine when high performance is needed. But at low and medium speeds the engine switches into diesel mode, in which the fuel is ignited by compression and heat alone. A 1.8-litre four-cylinder test version of DiesOtto fitted to a prototype Mercedes S-class saloon produced plenty of power, but also returned an average fuel consumption of 5.3 litres per 100km (equivalent in America to 44.4mpg)—extremely good for a such a big car. The vehicle’s emissions were also lower.
In a similar vein, Ricardo, another British automotive-engineering company, has been working with a group of partners on an engine that can switch from four-stroke to two-stroke running. Two-stroke engines can provide very high levels of torque. Ricardo reckons such an engine could not only improve fuel economy by 27% over a traditional engine but also greatly reduce its size and complexity. And because small engines take up less space in a car, that means there will be more room for occupants, inviting more innovative designs.
By putting all these technologies together, small cars capable of breaking the 100mpg barrier will become possible. Getting more than 80mpg from some small diesel-powered cars is already feasible—with a very light foot on the accelerator. Indeed, according to Edmunds.com, an automotive-information service, when you count the overall costs of owning a car, only one hybrid in America, the Honda Civic Hybrid, gets into the top ten of the least expensive vehicles to run, with fuel prices at $5 a gallon. It may be old hat, but the internal combustion engine still has a lot of mileage in it.