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B oth technologies will push up vehicle prices and for the
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first time when it comes to emissions legislation. both solutions will be more expensive to operate than their predecessors— up to now the trend had been for better fuel economy at each successive legislative change.
The Euro-4 and Euro-5 emissions limits call for levels of nitrous oxides (NOx) and particulate matter (PM) to be reduced substantially. And this is where the problems arise, because with currently available combustion technology you can't reduce one without upsetting the other.
Optimise an engine for fuel economy and you increase the combustion temperature, which sends NOx emissions rocketing. Reduce the combustion temperature to attack the NOx emissions and you affect the burn rate of the fuekinereasing PM emissions and damaging fuel economy.
Exhaust gases Selective catalytic reduction (SCR) uses a catalytic device in place of the silencer to break down the NOx emissions from the engine.This system requires a urea mixture. AdBlue, to be injected into the exhaust gases. In this test group Mercedes, Iveco,Volyo and Renault represented the SCR camp.
Exhaust gas recirculation (EGR) does just what it says on the box: it recirculates cooled exhaust gases back into the combustion chamber to reduce the heat when the fuel explodes in the combustion chamber of the engine, thereby reducing the NOx emissions. Some applications of this system require a particulate trap to capture any rogue PMs.
MAN and Scania are the two proponents of this technology although due to the cooling capacity required by EGR,Scania has had to resort to SCR technology on its flagship V8.
The claims and counter-claims regarding the efficacy of the different solutions are many and confusing. Operators could be excused for being worried about opting for one solution or another, because judging by the conflicting claims to date opting for the wrong solution could prove disastrous.
This test is designed to calm those fears and inject some hard facts into the argument. THE EURO-4 Mercedes-Benz Axor tractor unit made an immediate impression with its stunning deep blue paint job: no doubt highlighting its use of AdBlue technology (SCR).
Propelling this 40-tonner was the Mercedes-Benz 0M457LA 12-litre straight-six DI turbo-diesel coupled to Merc's manual eight-speed-synchromesh-plus-crawler box. The engine produces 400hp at 1,900rpm with 2,000Nry of lorque at 1,10Orpm, which ensured relaxed cruising on the flak though it required a touch more power on long uphill drags.
Ensuring the Axor meets the Euro-4 emissions standards is M-B's BlueTec SCR system. fed from a
95itre AdBlue tank mounted on the right of the tractor.
The layout of the cab is driver friendly; comfort is ennanced by fully adjustable steering whee and the inevitable air suspended seat. The manual gearstick protrudes from the side of the engine hump without getting in the way.
Secondary controls such as the radio, tacho and night heater are all within easy reach on the console and above the drive-'s head It's a sign of the times that the fuel card holder above the tacho has a number of slots for a selection of cards.
As vier as the usual fixed green, yellow and red bands on the rev counter to encourage fuel-efficient driving, a variable green band encourages the driver to change to a more economical gear: once the change has been made the green line disappears.
Passenger comfort is adequate for the occasional day trip. The seat's comfortable enough, but anyone over six feet tall might struggle with the limited legroom.
A huge upside is the excellent storage room and the copious supply of drinks holders. There are two in the centre of the cab, and two more, big enough to hold twolitre bottles, neatly hidden in the door sills. You get three overhead storage compartments and one under-bunk box, with an A4 tray for your maps and clipboards.
The central hump is wrapped in a grippyr wipe-clean surface, which is said to shrug off spillages of tea or coffee without leaving stains.
A single bunk is provided in the Axor, with luggage safety nets to stop luggage flying about if you need to hit
the brakes hard.
This example features windows in the rear, which will be handy for manoeuvring in tight spots and the thick black curtain looked capable of keeping the light outside for those cosy ;ate-morning lie-ins.
The Axor gave us a very pleasant ride, with low interior noise and relaxed cruising. When using the cruise control the driver can still change gear without having to cancel the pre-selected speed, which makes the lob that bit easier.
Mercedes-Benz's colour scheme of neutral greys is easy on the eye and leaves the driver to create his own in-cab ambience