Jonas Hofstedt

Late last year, Scania held a high level conference in Brussels to discuss how European road freight transport can cut CO2 emissions while remaining competitive. At the event MT caught up with Jonas Hofstedt, Scania’s senior vice president, powertrain development (pictured), to discuss the manufacturer’s approach to maximising the fuel efficiency of its Euro 6 trucks.

Despite the massive cuts in NOx and particulate emissions required under Euro 6, early tests of the new generation of heavy trucks indicate that the vehicles will use no more fuel than their Euro 5 predecessors. This has been achieved by both improving the efficiency of the whole vehicle, not just the engine.

"Euro 6 fuel consumption will no different at all from Euro 5," confirmed Hofstedt. "This will be done by improved aerodynamics, auxiliaries and information for the driver. Our Active Prediction [GPS-enabled cruise control that predicts hills] can be improved even further, so there will be variety of ways fuel consumption will be improved."

In fact Hofstedt said that the fuel consumed by a Euro 6 engine for a given power output "will be same" on average as Euro 5, a considerable achievement given the far lower tailpipe emissions that will require the use of EGR and a diesel particulate filter. "This won’t be same over complete range – lighter loads will see higher consumption and higher loads will be lower," said Hofstedt."But most customer applications will see equal fuel consumption."

Improving fuel efficiency of heavy truck engines has been held back since the 1980s and the arrival of the EU limits on local pollutants such as NOx and particulates.

"We decreased fuel consumption from the 1950s to the mid-1980s. But from mid-80s to now we have been struggling to achieve low nitrogen oxides and particulates, and during that time the average efficiency of the diesel engine has stabilised," said Hofstedt. "But Euro 6 will be the last step for NOx and particulate emissions and we have to focus on CO2. So  from now on you will see same trend from the 1950s to the 1980s on engine efficiency and if we have 45% combustion efficiency today we are definitely aiming for 50%."

Power electrification

One way this will be achieved is "power electrification" – a term Hofstedt has invented to cover a range of developments that will improve the efficiency of the engine.

"Power electrification is not only adding a big electric motor to the drivetrain and a big battery to recoup braking energy," he said. "You will see better integration of cooling for refrigerated transport, better applications for electrical PTOs etc. It is about being efficient with the electricity onboard. On a city bus for example we use two 24V generators and most of the time the engine is idling when it is 60% or 65% efficient. With a hybrid system with power electrification of the driveline and a diesel-electric convertor we can get 95% to 97% efficiency.

"With a hybridised drivetrain we can get rid of a lot of things – water pumps, fans, brake compressors, steering pumps etc – that are driven today in not as efficient a way as they could be. Power electrifying would increase the efficiency of the total vehicle."

Scania believes fuel savings can come not only from more efficient engines

Powertrain spec – 3%

Opticruise and Active Prediction 5-8%

Roof and side deflectors/skirts 8.5%

Reducing speed by 4km/h 5%

Reduced weight by 500kg 1%

Eco tyres 5%

Avoid extra equipment 1.5%

30cm boat tail 2%

Hofstedt said there are already "thousands of Euro 6 vehicles" on the road around Europe but admitted Scania has been "disappointed" that the market for Euro 6 hasn’t been bigger as yet. "That is partly because the German Maut not been set yet," he said. "When operators see how much they will earn per km they will be able to calculate the benefits of buying Euro 6."

Concerns over the added complexity may also be holding back sales of Euro 6, but Hofstedt was clear that the DPFs will not require additional action by operators.

"The DPFs automatically regenerate so operators don’t have to do anything between service intervals of 300,000 to 400,000km," he said. "The engine is no more complicated than a Euro 5 with EGR but the after-treatment is – it is a small chemical factory! The DPF has added to that – we have to control it with temperature and differential pressure sensors.

"We are lucky because we already have very low smoke levels – we achieved Euro 5 with EGR only so we know how to produce low smoke levels."