Noisy diesels are back!...

Noisy diesels are back! Modern engines have become nearly as smooth and silent as their petrol counterparts тЂ“ 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 itтЂ™s all for the sake of low CO2 output. One car that has been affected is the new Vauxhall Insignia (above).

A spokesman said: тЂњThe 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.тЂќ

And greater sound levels arenтЂ™t the only side effect, because vibration or diesel тЂ�clatterтЂ™ is set to rise, too тЂ“ as FordтЂ™s product program chief Joe Bakaj explained: тЂњThe thin gearbox oils we must use to get the economy figures demanded by Euro V means more vibrations make their way into the cabin.тЂќ

The AA also admitted that Euro V regulations are forcing manufacturers to make compromises, but a spokesman told Auto Express: тЂњOverall,

diesel engines still remain significantly smoother than they were in the past."