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Freelander2 : Refined New I6 Petrol Engine
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By MartinW at 2007-12-13 09:07
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Thursday, 22 June 2006
The powerful and torquey 3.2-litre i6 petrol engine is brand new for 2006, and gives Freelander 2 on-road performance comparable to that of many compact saloons. The vehicle accelerates from 0-60 mph in 8.4 sec (0-100 km/h in 8.9 sec) and has a top speed of 124 mph (200 km/h). More relevant for everyday motoring, it also has impressive kick-down acceleration. Maximum power is 233 PS (171 kW) at 6300 rpm, and maximum torque is 317 Nm (234 lb ft) at 3200 rpm. These figures are substantially higher than those offered by the outgoing Freelander’s V6 engine (177 PS/130 kW, 240 Nm). Performance is also much better than the outgoing vehicle’s, as is fuel economy – which is improved by 10 per cent on the combined average cycle.
The six-cylinder i6 engine is ingeniously designed to combine a straight configuration – intrinsically, the most refined and smoothest engine arrangement – with an exceptionally compact size. This allows the engine to be transversely mounted, which improves cabin packaging and gives extra space, in front of and behind the engine, designed to help optimise the efficiency of the vehicle’s safety systems.
The key to this compact new design is the unique and innovative Rear End Ancillary Drive (READ) system. Conventional engines drive camshafts and other engine ancillaries (including alternator, water pump and air conditioning compressor) from a series of chains and belts overhanging the front of the engine. The i6’s READ system takes drive to these items up the rear face of the engine – the side attached to the gearbox – with much less overhang. The result is an extremely short engine, just 600.5 mm long. This substantially increases engine bay space, allowing the i6 to be fitted crossways and the vehicle’s advanced crash structure to be configured around it.
The i6 engine has an aluminium block, head and bedplate and all are structurally optimised to balance low weight and stiffness. Even the camshaft cover is structural, allowing it to incorporate the camshaft bearing caps for further weight reduction.
There are twin overhead camshafts and 24 valves (four per cylinder) to provide optimal engine breathing. This is further improved by a patented Cam Profile Switching (CPS) system that features two completely different intake cam profiles machined onto the same camshaft. The engine management system decides which cam profile to use, depending on the engine’s running conditions and driver’s torque demands. One profile is ideal for low-speed/low-load driving; the other, which gives longer valve lift, is better for higher speeds and loads. An ingenious two-piece hydraulic valve tappet arrangement alters the cam profiles.
The i6 engine also features a continuously Variable Valve Timing (VVT) system, which constantly alters valve overlap to achieve optimum power, efficiency and emissions. The combination of CPS and VVT gives the new engine impressively broad power and torque bands, and improves both outright performance and general driveability.
In addition, the Variable Intake System – which alters both intake tract length and, more unusually, plenum volume – boosts low-end torque and high-end power, further enhancing the engine’s breathing capability. Eighty per cent of the vehicle’s maximum torque is available across the entire rev range, and 256 Nm (189 lb ft) is on tap all the way from 1400 rpm to 6400 rpm.
Aluminium pistons and forged steel con-rods operate a 7-bearing forged steel crankshaft with induction hardened bearing surfaces. The crankshaft timing ring and starter ring are incorporated into the flexplate that sits between the engine and automatic transmission for more compact packaging.
Power from the READ system is taken from a gear on the rear crankshaft web, which also drives the oil pump. This drives a mid-shaft gear that powers an idler-shaft carrying two different-sized gearwheels. The front gearwheel drives the alternator: the rear gear takes drive to the overhead camshafts through an inverted tooth chain, and also drives the power-steering pump, engine coolant pump and air-conditioning compressor via a polyvee belt.
The highly accurate fuel-injection system features four micro-nozzles per cylinder, each with a diameter of 0.29 mm. Capable of injecting a large volume of fuel when high performance is demanded – up to 250 cm3/min – they are also able to provide total precision when minimal performance is required, helping the i6 Freelander 2 achieve its combined fuel consumption of 25.2 mpg (11.2 l/100 km).
The base engine has been developed primarily by Land Rover’s Premier Automotive Group partner Volvo. Built at Bridgend, Wales – alongside the Land Rover / Range Rover V8 engine family – the i6 engine has been extensively developed for Land Rover’s demanding off-road requirements, including improved dust, mud and water protection and the tolerance of operation at more acute angles of tilt.
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