Diesel technology comes clean

New diesel-engine technology that helps to "clean" fuel during combustion will make filters that trap and burn off diesel soot to reduce harmful exhaust emissions, even more efficient.

British automotive components specialist Ricardo and carmaker General Motors are working on a low-emissions diesel engine capable of meeting Super Ultra-Low Emission requirements, the latest US clean-air requirement.

The companies are looking at improved air/fuel mixing, two-stage turbo boosting, advanced exhaust gas recirculation and cylinder pressure-based engine controls.

They are also developing filter-based exhaust after-treatment systems that, combined with improved engine combustion, will achieve emission levels much lower than the proposed Euro 5 law requires.

The ultimate aim is to build a diesel engine that meets ongoing worldwide exhaust-emission standards without compromising customer appeal, one that runs as least as clean as the best petrol unit but remains more fuel-efficient.

The engine under development has a competitive power rating of 65kW/litre. A 2-litre engine, in theory, would develop 130kW (175bhp).

The 2-litre four-cylinder turbodiesel engine in the latest Peugeot 307 range uses an exhaust filter which traps and burns off "particulates" or diesel soot. The 2.7-litre V6 turbodiesel in the 407 range uses the filter too. It is largely maintenance-free. The filter ensures cleaner air is filtered out of the exhaust with next to no harmful emissions, without compromise on power. Peugeot says it filters out more than 90 per cent of soot.

The use of the cleaner-burning technology meets the current Euro 4 emissions standard and its appearance here is due mostly to recent improvements in the quality of New Zealand's diesel fuel.

Particulate filters were available in Peugeot models in Europe six years ago, when Europe had a sulphur limit in diesel of 50 parts per million. Back then, the sulphur standard here was a dirty 3000ppm. Now it's 50ppm. The 307 engine develops 100kW (136 bhp) at 4000rpm and 320Nm of torque at 2000 rpm and is mated to a six-speed automatic transmission with manual mode.

The V6 in the 407 sedan and wagon produces 150kW (200bhp) and a whopping 440Nm at 1900rpm - 52 per cent more torque than the 3-litre V6 petrol unit - and is also coupled to a six-speed unit.

Peugeot says fuel economy in the 307 is among the best in the class, returning overall economy figures of 6.7 litres/100km. The 307 range is priced between $39,990 and $44,990.

The V6 diesel first appeared in New Zealand earlier this year in the 407 coupe. The sedan is priced at $66,990 and the wagon at $69,990. Peugeot says the 2.7-litre engine returns 6.5 litres/100 km (43.4mpg), and 8.4 litres/100 km (33.6mpg) in the combined test. Around town it is expected to get 11.7 litres/100 km (24.1mpg).