TOKYO -- Hybrid vehicles beware: Your claim to fame as fuel sippers may soon be usurped by minivehicles powered only by gasoline engines.

Daihatsu's Mira e:S

Japan's two minivehicle giants, Suzuki Motor and Daihatsu Motor, are introducing new engine technologies and other innovations that promise to improve the fuel performance of their cars by 20-30%.

Come fiscal 2015, both automakers aim to have minivehicles on the market that can travel 40km on a liter of gas, outperforming the fuel efficiency of even the best of today's hybrids, like the Toyota Aqua and the Honda Fit Hybrid.

The innovations are coming none too soon, since Japan's yearly tax on minivehicles is set to rise from next April.

Daihatsu has reworked the combustion mechanism in its engines, using electromagnetic waves much like a microwave oven to improve fuel combustion. It has also introduced a generator that exploits changes in exhaust gas temperature to make electricity to power the wheels and run instrumentation inside the car.

To further boost fuel efficiency, Daihatsu is making greater use of plastic parts in place of sheet metal wherever possible. For example, starting from the June release of the new-model Copen roadster with its retractable hardtop, the automaker intends to use plastic fuel tanks in all of its cars.

The company's flagship Mira e:S already boasts a fuel efficiency of 33.4 kilometers per liter and the goal is to improve that to around 42 kilometers per liter.

Meanwhile, rival Suzuki is making improvements of its own to its Alto Eco minicar and can now achieve a fuel performance as efficient as 35 kilometers per liter.

Suzuki's Alto Eco

By cooling and recirculating exhaust gas inside the engine, Suzuki holds engine temperatures down and reduces gas-wasting incomplete combustion. Finer spray of the injected fuel also improves efficiency, and the engine gets further help from a technology for utilizing the energy released during deceleration.

The Daihatsu Mira e:S and the Suzuki Alto Eco have competed against each other on fuel efficiency ever since September 2011, when Daihatsu unveiled a model that could travel 30 kilometers per liter and dubbed it the "third eco-car."

But in seeking to break above 40 kilometers per liter, both companies are preparing minicars that can perform better than hybrids, and which they hope will keep buyers interested even after taxes on minivehicles rise next year. With that kind of fuel efficiency, the savings achieved in gasoline costs over the course of a year should compensate for the higher taxes that minicar owners will need to shell out.

(Nikkei)