Diesel car sales fall but new tech could make it cleaner and greener

Diesel cars

Diesel cars are blamed for poor air quality courtesy of their exhaust emissions

Diesel car sales are falling as drivers turn their back on it because of health concerns. But diesel power is about to hit back with new technology designed to reduce harmful exhaust emissions.

Official figures show that sales of diesel cars were down in the UK by a fifth in May 2017 and by 15 per cent in June. That’s compared with the same period in the previous year. The slump is believed to have been caused by various factors. The high-profile Volkswagen diesel cheat device case raised people’s awareness of the harm of the nitrogen oxide (NOx) pollutants diesel produces. But people are also concerned that diesel cars may be slapped with hefty taxes.

However, we can reveal that diesel is hitting back. Automotive technology giant Continental has worked out how to make a much cleaner diesel car.

Why do we need diesel?

Alternative fuel vehicles (AFV) such as plug-in petrol-electric hybrids and full electric cars are becoming ever more popular. While diesel sales dropped, the number of electric and hybrid cars rocketed by nearly a third (29 per cent) in June. But that’s only part of the story. Despite their massive proportional increase, there were still only 8311 AFVs sold in June 2017. That compares with 103,564 diesel cars. The principle reason is the still relatively expensive battery technology needed for AFVs. José Avila, president of Continental’s powertrain division, said: “The diesel engine will continue to play an important role in meeting mobility needs for the foreseeable future. So it is vital for us to develop the technology to support extremely low-pollutant diesel operation.”

Diesel can be made cleaner

To limit the NOx particles that diesels spew out, many modern cars are fitted with a system called Selective Catalytic Reduction. This uses a liquid called AdBlue which is injected into the exhaust gases to remove NOx. Continental has worked on a regular modern diesel engine with this tech in a Volkswagen Golf. Following some clever tweaks it’s reduced nitrogen oxide emissions by 60 per cent.

How it’s done

By replacing the car’s existing fuel injection system with one that injects fuel more precisely at much higher pressure, Continental has worked out how to make Selective Catalytic Reduction even more effective. There is also a tiny electric motor, known as a mild hybrid. This helps the diesel engine under hard acceleration when NOx output is at its maximum. Boffins also worked out that if they heated the catalyser in the exhaust, it would help reduce NOx even more.

Diesel car sales

New tech has reduced the emissions of this VW Golf by 60 per cent (Picture © Continental)

What the results are

Currently, all new diesel cars must conform to legislation called Euro 6. This states they must pump out no more than 80mg/km of NOx. To show how clean modern diesels are becoming, the previous Euro 5 standard for cars built before September 2011 are rated at 180mg/km. Continental’s adapted VW Golf puts out just 30mg/km. And unlike other NOx reduction tech which harms economy, this kit reduces fuel consumption by 4 per cent.

Where do we go from here?

Continental says it’s almost ready to put this technology into production. If so, it’ll be good news for the many fans of diesel power. And pollution aside, it does have plenty of positives, hence its popularity up to now. Diesel is richer in energy than petrol. That means you get more power for less fuel. In turn you have to visit the pumps less often than with petrol cars. Diesel is also a proven technology: garages know how to fix diesel cars and the refuelling infrastructure is in place. Sales may be falling for now but diesel isn’t quite dead yet.

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