Definitely diesel

By ALASTAIR SLOANE

It happened with the Alfa Romeo 156 and the BMW 3-Series. Now it's happened with the luxury Peugeot, the 607. It's the development of diesel. In just a few years carmakers have taken the ultra-efficient combustion process developed by German engineer Dr Rudolph Diesel in 1892 and given it new life.

No longer are diesel engines noisy, smelly and grubby. They are quieter, more fuel-efficient, cleaner, and make more sense than ever before.

The pick of the models at the launch of the 156 in Portugal in 1997 was the 2.4-litre common-rail diesel engine. It was called the JTD but never made it to New Zealand. Who wants a diesel Alfa, asked the importers.

In Spain in 1998, when BMW unveiled its new 3-Series, the 2.0-litre oil-burner blew the peakier 323i and 328i petrol models into the weeds. But BMW didn't want an oil-burning 3-Series in New Zealand.

It was the same story on the desert roads of Jordan last week, when Peugeot unveiled its new top-end 607 model.

From some angles the 607 looks like the Audi A6, although the Peugeot is better looking overall. New Zealand is likely to get only the 607 with the 152kW 3.0-litre petrol engine.

It has all the traditional Peugeot qualities, including excellent ride and handling, but the 3-litre model's power-assisted steering lets it down.

The servo unit in the 3.0-litre 607 works on the car's road speed and it lacks feel, certainly after being loaded up through bends.

The servo units in the 98kW 2.2-litre common-rail diesel and 116kW 2.2-litre petrol work on engine speed and have considerably more feel.

Certainly the diesel, with its ground-breaking particle filter, and the smaller petrol model were all-round better cars to drive.

Peugeot and its stablemate Citroen build 800,000 diesel engines a year, the highest output in the world. Eight years ago in Europe, diesel cars accounted for 15 per cent of all sales.

This year diesels will account for 25 per cent of the new-car market. In Austria, 55 per cent of new cars are diesel-powered. In Spain it's 47 per cent and in France 41 per cent.

Dr Robert Buechelhofer, a member of the Volkswagen AG board and director of the carmaker's Asia-Pacific region, believes the diesel engine has a future in New Zealand, where its lazy pulling power is suited to twists, turns and hilly terrain.

"It might not be popular now," he said on a visit, "but wait until the luxury carmakers start to build sophisticated diesel engines for their top models. Then people will start to take notice. It will have a flow-on effect."

Mercedes-Benz, BMW, Audi, Jaguar have already confirmed the presence of multi-valve common-rail V8 diesel engines as an option in their premium models.

But Peugeot has been acknowledged as the first carmaker to use the particle filter, which removes and ultimately incinerates the soot particles in diesel.

The filter is a porous structure made of silicon carbide and sits in the catalytic converter. It retains and periodically burns off the particles when the exhaust gas reaches a certain temperature.

The filter is designed to last the life of the car, but to ensure efficiency it should be water blasted every 80,000km.

Common-rail is a computerised fuel-injection system which lowers fuel consumption pollutant emissions, aids ride comfort and suppresses much of the noisy clatter associated with traditional diesel engines.

Briefly, conventional diesels use a mechanical pump to distribute fuel to each injector. But this is a complex process and the flow of fuel in the combustion process can't be precisely controlled. Mixing in a combustion chamber a large and irregular amount of fuel with compressed hot air is what made conventional diesels

noisier than petrol engines.

Common rail does away with the mechanical pump and uses electronics to pre-heat and filter the fuel in a sealed metal tube called a "rail." The fuel is then electronically injected from the rail into each combustion chamber, using micro-second timing to regulate the combustion process to the point where the loud detonation is converted to a long roar. Subsequently, the engine runs much quieter.

Dr Diesel was born in Paris in 1858 and died on a boat in the English Channel in 1913. He disappeared overboard while on his way to meet British car industry executives in London. His body was never found.

There were many theories about his disappearance, most involving cut-throat conspiracies.

The Germans killed him to prevent him giving the English details of an advanced model diesel, it was said.

Others claimed that the English silenced him because his diesel threatened development of spark plugs and the petrol engine. Yet others said the Americans did away with him for the same reason.

His first commercial engine appeared in 1896. Dr Diesel had been working as a refrigeration engineer in Switzerland when he hit upon the idea of compressing air inside an engine

to the point where it became hot enough to ignite fuel oil sprayed into the combustion chamber.

The idea instantly made spark plugs obsolete. Diesel's process was more efficient too, the whole expansion ratio giving the diesel engine a higher thermal efficiency than petrol, up to 40 times in the case of heavy-duty engines.

It is this thermal efficiency which carmakers are further developing today.