Diesels turn up volume again

By Jack Rix

31st October 2008

Noisy diesels are back! Modern engines have become nearly as smooth and silent as their petrol counterparts – but all that looks set to change.

Strict new Euro V emissions regulations, which come into effect next year, are forcing manufacturers to compromise on how silky-smooth their oil-burners can be. And it’s all for the sake of low CO2 output. One car that has been affected is the new Vauxhall Insignia (above).

A spokesman said: “The 2.0-litre CDTi engines need to take full advantage of sophisticated combustion strategies, multi-fuel injections and high exhaust gas recirculation rates to reduce nitrogen oxides and comply with Euro V emissions, while at the same time maintaining excellent mpg and performance. So, noise may increase slightly due to delayed combustion and a higher in-cylinder pressure gradient.”

And greater sound levels aren’t the only side effect, because vibration or diesel ‘clatter’ is set to rise, too – as Ford’s product program chief Joe Bakaj explained: “The thin gearbox oils we must use to get the economy figures demanded by Euro V means more vibrations make their way into the cabin.”

The AA also admitted that Euro V regulations are forcing manufacturers to make compromises, but a spokesman told Auto Express: “Overall,
diesel engines still remain significantly smoother than they were in the past."

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