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Freelander2 : New TD4 Diesel Engine
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By MartinW at 2007-12-13 09:06
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Thursday, 22 June 2006
The second engine for the Freelander 2 is an all-new 2.2-litre TD4 turbodiesel, which combines great torque and impressive refinement.
Maximum power for the new diesel engine is 160 PS (118 kW) up from 112 PS (82 kW) on the outgoing Freelander’s 2.0-litre diesel. Maximum torque is 400 Nm (295 lb ft) – up from 260 Nm (191 lb ft). Naturally, performance is improved substantially. Acceleration from 0-60 mph takes 10.9 sec in manual guise, substantially reduced from 13.2 sec for the previous Freelander diesel (0-100 km/h now 11.7 sec, from 14.4 sec). The combined average fuel consumption is 37.7 mpg (7.5 l/100 km), better than the outgoing Freelander diesel despite a 43 per cent increase in power.
The TD4’s advanced technologies include variable in-cylinder swirl, the latest ‘generation 3’ common-rail fuel injection, a new Garrett variable-nozzle turbocharger, a double-walled cylinder block and sump-mounted balance shafts. The result is impressive torque spread, fuel economy, performance and refinement. The engine exceeds the demanding EU4 emissions requirements, and a maintenance-free catalysed Diesel Particulate Filter (cDPF) is also available for even cleaner performance (all diesel engine data quoted is without the optional cDPF fitted).
The peak torque of 400 Nm (295 lb ft) occurs at a very usable 2000 rpm. The power curve is flat, delivering 80 per cent of peak power across more than half the rev range. A hefty 200 Nm (148 lb ft) of torque is available from 1000 rpm to 4500 rpm. As a result, the Freelander 2 TD4 is responsive, rewarding and easy to drive.
In automatic versions of the Freelander 2 TD4, hard acceleration delivers extra performance for short periods thanks to Transient Overboosting, where turbo pressure is increased. The new GT17B Honeywell Garrett Variable Nozzle Turbine (VNT) turbo gives great low-speed response, huge mid-range torque and plentiful upper-end power. Its small turbine wheel is light, further reducing turbo lag, which is virtually unnoticeable.
The engine combustion is very efficient, with piezoelectric injectors, high fuel pressures and variable swirl technology all reducing combustion noise and in-cylinder pressure. Piezoelectric injectors provide exact control of the fuel delivery, while the ‘generation 3’ common-rail injection system is capable of injection pressures of 1800 bar (over 26,000 psi), about 30 per cent higher than ‘generation 2’ systems. Common-rail systems can supply a high volume of fuel at peak load conditions, one reason why common-rail engines offer much better performance – as well as better economy – than older diesel engines.
The new cylinder head design optimises swirl across the entire engine range. In many diesel engines, this is a compromise between achieving acceptable swirl at low speed and avoiding excessive swirl at high gas flow rates. On the TD4, an innovative intake port deactivation system solves this problem, improving diesel swirl – and combustion efficiency – at both low and high revs.
Each cylinder has two intake ports. The low-speed tract applies air at an acute angle to create swirl at low engine loads. Once higher gas flows are demanded, a second tract opens, providing extra air – but without increasing swirl.
The cylinder block is manufactured from cast iron, and is double walled. This not only strengthens the block but significantly reduces radiating noise, a little like double glazing. The head is aluminium alloy while the engine cover is made from lightweight polypropylene, housing foam to absorb specific noise frequencies. It is simple but highly effective, reducing engine noise by up to a half.
The crankshaft is made from fillet rolled cast steel and is supported on five main bearings. A dual-mass flywheel absorbs engine vibrations. At the other end of the crankshaft, a torsional vibration damper isolates the crank from the valve-train and ancillary drives. To aid engine refinement further, the TD4 uses two counter-rotating balancing shafts, housed in the sump. These shafts, rotating at twice crank-speed, counter the natural four-cylinder engine vibrations. They help deliver a remarkably smooth and refined diesel engine.
The engine – which makes its world debut in 2006 – is a result of the co-operative agreement between the Ford Motor Company and PSA Peugeot Citroën which also produced the acclaimed TDV6 fitted to Discovery 3 and Range Rover Sport. As with the i6 petrol engine, the TD4 engine has been specially developed to meet Land Rover’s unique requirements for wading and extreme off-road angles, as well as for class-leading dust and mud protection.
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