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EVOLUTION THEORY

13th January 2005
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Page 61, 13th January 2005 — EVOLUTION THEORY
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As the R-Series begins its year of glory as International Truck of the

Year, Colin Barnett has been to Sweden to take a look behind the scenes at Scania's headquarters. He also got to drive some trucks...

When Scania launched the R-Series last year, the company revealed there would be no more completey new model launches. Instead there was to Je an ongoing process of continuous mprovement.The fruits of that policy are tow ripening as the first of those "improvements" enters production.

Scania referred to operator and media feedback, and benchmarking of the R-Series igainst its rivals, interestingly illustrated by )hotographs from our recent 1000 Point Test. It admitted that a number of features had evoked less than universal acclaim. These nclude storage facilities, design of the main )unk and a lack of certain electronic features. As a result, some relevant items of the R-Series ;pecification will be changed forthwith.

sins under fire some of the greatest criticism was aimed at the ;ize and open-fronted design of the overicreen storage bins, which will now be fully lidded. Gaps at the outer ends of the sun visors will be bridged with sliding extensions For a long time, CM'S testers have bemoaned the lack of a 'cruise control engaged' signal on Scanias, among others. It was a surprise when the R-Series was launched without this simple feature, but it has now arrived in style. Not only is there a graphical display of the cruise control set speed but, on retarder-equipped vehicles, it is combined with a downhill speed control, adjustable in 2km/h increments from 3-15km/h above cruise speed.

Unfortunately the cruise control is still operated from an ergonomically unsound position at the bottom of the steering wheel pad, but we're sure the new "listening" Scania will find a better location in due course.

Even Scania's approach to the question of how long its Opticruise automated transmission will retain a clutch pedal seems to be softening."When we have the right solution, we will introduce it," was the official response.

Benefits of HCCI Before Christmas we reported on Scania's plans to meet emission standards up to Euro-6 with developments of its current technology and the introduction of its XP1 high-pressure common-rail injection. Although this relieves some of the pressure on the development of the revolutionary HCCI engine it still has potential benefits that deserve continued research.With sooty particulates and CO, effectively under control with today's technology, the greatest challenge remaining is to eliminate NOx emissions — which is where HCCI (homogenous charge compression ignition) is promising. For the HCCI development programme Scania is collaborating with the Lund Institute of Technology and the Royal Institute of Technology in Stockholm.

HCCI is a fancy name for a simple concept. "Homogenous charge" simply means that the fuel and air is mixed before entering the combustion chamber, in a similar way to a conventional petrol engine. However, the charge is still ignited by the heat of compression, like a diesel. Scania already has a prototype engine running, and we were allowed to take a look at it during our recent visit to the Sodertalie technical centre.

Typically of research engines,the current HCCI unit is a relatively simple affair:a twolitre single cylinder using standard Scania components below cylinder-head level.The top end features a special head with four independently operated hydraulic valves developed by Lotus Engineering. Although each of these valves takes about 10hp to operate, their lift and timing can be fully variable. A fundamental issue is which fuel best suits this technology; research is currently centred on light fuels.such as petrol and ethanol.The test engine was running on ethanol during our visit, at a compression ratio of 16:1.

NOx is created by the nitrogen in the air being heated during combustion. It starts to form at temperatures above 1,525°C—current diesel engines can reach peak temperatures around 2.125°C. Whereas diesel combustion is a relatively slow affair, with one or more flame fronts moving around the cylinder, the HCCI's objective is more of an instantaneous explosion with no flame front.Suitably controlled, this gives a more constant temperature throughout the process,and importantly, keeps peak temperatures below the NOx formation level.

Goodbye to NOx

During the run we observed, at 1,000rpm under a 50% load, the NOx emission was a barely measurable trace. Economy is also excellent, with the HCCI giving a potential thermal efficiency of 48%.

However, there are downsides The combustion knock produced by the test engine highlights the need to overcome issues with mechanical durability, noise and vibration before it becomes a practical proposition.

The key to the viability of HCCI lies in control of the combustion process to a degree of accuracy that is not yet feasible. But with the power of the microchip said to double every 18 months, it's a safe bet that a solution will be found within Scania's time frame of 8-10 years before HCCI is production ready. •


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