A new development in diesel engine technology could drastically reduce NOX emissions, it has been claimed.

Engineering firm Bosch says its new system is capable of delivering NOX levels around ten times lower than those required even by new, more stringent limits set to come into force in two years’ time.

Currently, European legislation requires  new passenger cars emit no more than 168mg/km of NOX, and this limit is set to be cut to 120mg/km in 2020.

However, Bosch says cars equipped with its new technology can achieve as little as 13mg/km in standard Real Driving Emissions (RDE) tests. Even if the cars are driven in challenging urban conditions, in excess of legal requirements, the average emissions of test vehicles are as low as 40mg/km.

Bosch says its technology can provide a road to recovery for diesel cars, which have seen slumping market demand, due to uncertainty over lawmakers’ response to emissions concerns.

Bosch CEO Volkmar Denner said, “There’s a future for diesel. Today, we want to put a stop, once and for all, to the debate about the demise of diesel technology. 

“Bosch is pushing the boundaries of what is technically feasible. Equipped with the latest Bosch technology, diesel vehicles will be classed as low-emission vehicles and yet remain affordable.”

Denner said diesel still had a key role to play in the car market, with electric vehicles not yet a mainstream solution.

“We firmly believe the diesel engine will continue to play an important role in the options for future mobility,” he said.

 “Until electromobility breaks through to the mass market, we will still need these highly efficient combustion engines.”

Bosch says its system is based on components that are already on the market and, therefore, it is available to manufacturers immediately.

It says the use of existing technology also means diesel cars should not become less affordable, while fuel economy and CO2 emissions are not negatively affected.

Explaining the technology, a spokesperson said an important factor that has hindered the reduction of diesel NOX emissions is driving style, which its system addresses.

A spokesperson said, “A dynamic driving style demands an equally dynamic recirculation of exhaust gases. This can be achieved with the use of an RDE-optimised turbocharger that reacts more quickly than conventional turbochargers. 

“Thanks to a combination of high and low-pressure exhaust-gas recirculation, the air-flow management system becomes even more flexible. This means drivers can drive off at speed without a spike in emissions.”

An equally important issue, according to Bosch, is temperature. The spokesperson explained, “To ensure optimum NOX conversion, the exhaust gases must be hotter than 200°C. In urban driving, vehicles frequently fail to reach this temperature. 

“Bosch has therefore opted for a sophisticated thermal management system for the diesel engine. This actively regulates the exhaust-gas temperature, thereby ensuring the exhaust system stays hot enough to function within a stable temperature range and that emissions remain at a low level.”

From a UK fleet perspective, Shaun Sadlier, head of consulting at Arval, gave a cautious welcome to the Bosch announcement.

“The increasingly negative attitudes towards diesel that have developed over the past couple of years have been prompted by supposed issues with NOX emissions, even though current Euro 6 engines are a massive step forward in this respect,” he said.

“Therefore, any technology that can create further NOX gains needs to be taken very seriously, especially if it comes from a well-known and respected name such as Bosch. 

“The questions for fleets would be around how quickly this technology could be brought to market, any additional cost over current diesels and whether public perception around diesels can ultimately be changed.”