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13/07/2016
SCANIA ADOPTS THE SCR SYSTEM

Truck Engineering

 

The Swedish company, for some of its engines, has decided to go against the tide, following Iveco’s idea of foregoing EGR systems. With promising results. In Europe, meanwhile, a new diesel scandal is looming over the horizon

Fabio Quinto

Thank you, AdBlue. While liquid-gas-powered trucks (LNG) are increasingly emerging as the successors of today's Euro 6 vehicles (since, at least for the next few years, we will hardly see a "Euro 7"), a urea based additive is dividing the Italian trucking sector. Almost all manufacturers have chosen to meet the strict EU emission standards using Exhaust Gas Recirculation systems (EGR), SCR catalysts and Diesel Particulate Filter (DPF). Scania, Daf, Man, Mercedes-Benz, Volvo Trucks and Renault Trucks. Only Iveco took another direction using SCR systems only, in addition to particulate filters, putting EGR systems aside. Hard to say which, in the end, was the winning choice. What is certain is that the SCR-only front has been progressively widening since 2012. By the end of 2014, in fact, Scania had announced the launch of its R450 without EGR: in both cases, the engine is a DC13, a 13-liter 6-cylinder in-line version of the 147. And this is not an isolated case, in fact, taking the lead a few months earlier, at the beginning of 2014, Scania launched its G410, still based on a 13 liters in line engine, but this time with 410 hp. Now, though, the R450, Scania’s flagship, is really taking off on the ups and downs - not just figurative - of the Italian market.

 

 

Top class performance for the R450

Eliminating the EGR system has, on the other hand, improved the vehicle’s performance in terms of torque and power, besides simplifying the design of the engine itself. No more pipes with hot exhaust gases in recirculation nor valves and heat exchangers, and no need for larger radiators too. Even a variable geometry turbocharger becomes unnecessary as a traditional one is more than sufficient, since the engine is no longer receiving contaminated air from the EGR, and no longer needs a higher boost.  Furthermore, the compression ratio also increased from 17 to 18:1, not to mention that eliminating the EGR cooler saves about 40 kg on the vehicle’s tare for a 4x2 tractor with Streamline cabin. The improved performance of the engine is especially appreciated on our many mountain passes. The new engine model has, just like its predecessor, a very impressive torque: maxi­mum torque is 2,350 Nm and is available right from 1,000 r/min, which assures very good driveability.

 

 

AdBlue consumption

 

The down side, in theory, is represented by a higher consumption of AdBlue. But recent tests around Europe have shown it to be not much higher than vehicles equipped with EGR systems. Actually, in some cases it was even lower. Engines using only SCR technology normally require more AdBlue, and in the case of Scania, this means an average of 6 percent of the total amount of diesel, while engines with EGR and SCR normally need 3 percent. Joel Granath, Head of Product Management for Scania Trucks, stated: ““According to our own calculations running a Scania Streamline results in a 1 percent fuel saving compared with the previous model using both EGR and SCR – everything else being equal”. Not bad for a company that has long resisted the temptation of switching to SCR insisting on the qualities of EGR systems.

                                                                       

 

Getting around the laws

Sure, talking about diesel engines and emissions is impossible without thinking back to the recent diesel-gate scandal. But if industrial vehicles in the last two decades have always been trailblazers of new technologies, also in terms of getting around the laws - unfortunately - the sector distinguished itself, especially in relation to SCR systems. In Germany, in fact, the Camion Pro transport association reported the existence of devices, manufactured in China and worth a few hundred Euro, which are able to turn off the SCR, thus bringing to zero the consumption of the urea based additive. Furthermore, since the catalyst is placed “downstream” of the engine, there are no consequences on fuel consumption or performance. All you have to do is Google "AdBlue emulator". Now imagine the possible consequences on pollution: trucks that look like squeaky clean Euro6, suddenly become, as far as NOx is concerned, as old and “dirty” as Euro1 or Euro2. Moreover, the scam is very difficult to thwart, at least for now: the control unit does not display any error codes and the police forces can thus do very little about it, unless they suddenly receive a massive amount of exhaust gas analyzers. What is certain is that, with behaviors of this kind, it is little wonder that cities like Paris are now speaking of abolishing diesel from 2020, or the Netherlands, where the Government is making moves to ban all non-electric vehicles by 2025. Will common sense prevail in the end, and along with it proper inspection procedures? 

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