Introduction
If the Euro-3 emission standard is to be remembered for anything, it will be for delivering the final blow in the long-drawn-out death of the low-tech engine. Ever since Bosch converted Rudolf Diesel’s principles into a practical system in the Twenties, the mechanically controlled fuel-injection system has changed little. But the level of cleaner combustion needed to meet the demands of Euro-3 has finally reached the point where only electronics can provide the necessary degree of control – tolerances that the pioneers could never have dreamed of.
The finest brains in the industry are engaged in a never-ending effort to match the seemingly irreconcilable goals of lower emissions and more power without using significantly more fuel. TO achieve this, each company is picking from a finite selection of techniques. Scania’s latest effort is basically no different, although its chosen recipe does have a flavour all of its own, thanks to a dash of turbo-compounding, an ingredient at present unique to the Swedes.
Product Profile
We described the technology behind the new 470 engine when we first drive it (CM 22-29 Feb); but to recap briefly, it uses a high pressure injection (HPI) system developed in association with Cummins. The engine actually has two fuel circuits, one providing the fuel for combustion and the other acting as an electronically managed hydraulic system controlling the injection timing and quantity. Open-nozzle injectors permit a gradual onset of injection, which benefits noise levels.
The 470 is the first engine, but certainly not the last, to feature Scania’s in-house engine management electronics, while the third weapon in its armoury is the latest version of the turbo-compound system. Mounted downstream of the conventional turbocharger, this uses some of the remaining energy in the exhaust gas to spin a second turbine. The rotation is transmitted back into the flywheel by way of a hydraulic coupling, like a mini torque converter, and a reduction gear. Scania’s figures indicate about 3% of engine power is reclaimed. A welcome by-product of turbo-compounding is that by the time the exhaust gas has powered two sets of turbines, it barely has the energy to drop out of the end of the pipe, never mind make any noise.
The total sum of all this wizardry is an engine that has the weight and compact dimensions of the current 12-litre six-pot but with a torque output similar to the old 530hp 14-litre V8. On the emissions front it comfortably meets Euro-3 and, with the likely addition of exhaust gas recirculation, will be up to the challenge of Euro-4 as well.
Starting at the 12-litre 420, the top end of Scania’s like-up now goes to our 470 at an extra cost of about £5,500. Another £3,300 buys the 16-litre V8 480, while the range-topping 580 adds a further £3,800. The natural comparison is between the 470 and 480 units. Apart from the obvious 10hp, the V8 offers an extra 100Nm of torque, albeit over a narrower speed range, the same specific fuel consumption and an extra 30kW of exhaust brake power. Against this, the six-pot weighs in at about 250kg less. You pays your money…
Productivity
Our summary of the then all-new Scania 580 (CM 05-11 October 2000), our first Euro-3 compliant test subject, praised the V8-engined flagship both for its easy performance and for its fuel consumption. The performance was expected, of course, but the economy was a pleasant surprise.
The 470 was just as surprising in its own way. We were expecting that a highly efficient engine should produce good fuel results, and we were not disappointed. Intriguingly, all three Euro-3 tractors that we’ve tested so far have been within 0.1mpg of each other. So although at 7.45mpg overall the Scania 470 is the worst of the three so far, that deficit equates to just one gallon over three days!
Where we didn’t expect the result that we achieved was in the journey times. The average speed over the whole trip was just 0.2km/h slower than in the big V8. On the A68’s severe gradients section, the 470 actually beat the 580 by nearly 5km/h. This is undoubtedly due to the V8’s lazy nature, which gives rise to a relaxed driving style, whereas the high-tech six, however willing, needed to be driven all the way. On motorway sections it just got on with the job on its own, and, quite simply, few trucks could have made the journey from the Midlands to Scotland any faster than the 470 did – not legally, anyway.
At 41 tonnes, the 470 tackled the test with a payload of 25.33 tonnes, a quarter-tonne more than the V8 580 and a competitive figure for a well-specified cab. Scania would have liked to have run the new 470 at the new 44-tonne limit, believing it is even more efficient under heavier loadings. However, for the sake of comparison, we stood by our decision to run all our tests at a maximum of 41 tonnes, at least for this year.
