Mitsubishi Motors Corporation (MMC) has announced two new fuel-saving technologies: the 4J10 lightweight and compact 1.8-litre petrol engine incorporating a new version of the company's MIVEC variable valve timing system and the latest version of the company's Auto Stop & Go (AS&G) idle-stop technology.

"The development of these latest technologies is expected to play a big part in achieving MMC's own upcoming fuel and environmental efficiency targets," the automaker said in a statement.

The new 4J10 engine/AS&G combination will power the Japan-market RVR (ASX or Outlander Sport in some markets) compact SUV, the Galant Fortis sports sedan (Lancer or Lancer EX), and Galant Fortis Sportback (Lancer Sportback) five-door sports hatchback. With this engine, the three models show an improvement of 12% in fuel efficiency (measured by Japanese 10-15 mode). The RVR was launched on 20 October and the Galant Fortis models follow on October 27.

 The development of these technologies stems from the Mitsubishi Motors Environment Initiative Programme 2015 that forms a key part of the company's Jump 2013 mid-term business plan. Targets for achievement by 2015 set forth in the programme include a 25% reduction in on-road CO2 emission of new vehicles compared to the global weighted average for the 2005 fiscal year. The programme is the mid-term benchmark for the Mitsubishi Motors Group Environmental Vision 2020 which aims for a 50% reduction in CO2 emission against the global weighted average for the 2005 fiscal year.

MMC is also increasing the number of models powered by clean diesel engines that meet the latest emissions regulations in Japan and Europe and further advancing its petrol engine technology. At the same time, MMC is pushing ahead with development and rollout of electric vehicles, the introduction of the MINICAB-MiEV light commercial EV and plug-in hybrids.

The new MIVEC system together with improved combustion stability and a reduction in piston friction provide an improvement in fuel economy without any loss in engine performance (output and torque) over the 4B10 MIVEC engine.

MMC first applied its MIVEC variable valve timing system to an engine in 1992 with the aim of achieving higher engine efficiency at any engine speed. To date, the company has employed two types of MIVEC systems. In one, the system switches between different valve lifts and valve opening durations according to engine speed, while in the other (as used in the 4B10 engine) the system varies the valve opening timing on a continuous basis.

The new MIVEC system employed in the new 4J10 engine can do what the previous two systems could do – but at the same time, all the time. This is due to a single mechanism that mechanically couples intake valve lift, opening duration and timing, allowing these three parameters to be varied simultaneously and continuously. As a result, the new system provides ideal valve operation control that also reduces pumping losses by using intake valve timing to control intake volume; thereby further improving fuel economy. In addition, the new MIVEC system can be applied to SOHC valvetrains; bringing about a reduction in both engine weight and size due to the reduction in the number of parts.

The new 4J10 MIVEC engine is produced at the Shiga powertrain plant and the company plans to sequentially introduce it on other models.

Auto Stop & Go (AS&G) is an idle-stop mechanism that reduces fuel consumption by automatically shutting off the engine when the car is stopped. MMC currently employs this technology on some manual transmission models for the European market.

The latest version has been developed for use on models fitted with continuously variable transmissions (CVT). The addition of a new control unit (the AS&G ECU) to vehicle management systems means that the new AS&G is also integrally controlled along with the engine, CVT, active stability control (ASC) and climate control. Other changes include the use of a more durable 12V battery and a DC/DC converter (to prevent breaks in audio system sound and prevent the in-car navigation from resetting itself when the engine restarts).

Combining AS&G to the new MIVEC engine provides quick engine restart and initial acceleration performance that feels no different from a car without AS&G. In addition, fuel efficiency is improved because the new MIVEC engine allows the engine to restart using less intake air and fuel by keeping a low valve lift at engine restart. The new AS&G also controls brake force from engine stop to restart via the car's integrated control system. This means that the car will remain stopped on inclines until power is applied to the wheels.