Our former development engineer and Automotive plant director Andy Goundry caught up with some project managers at a recent Land Rover Jaguar Group test event and road tested the new Range Rover Hybrid:
There seems to be a popular belief amongst much of both the media and the general population that hybrid vehicles are the way ahead in terms of fuel economy and emissions reduction. In reality, however, this is far from universally the case, because hybrid drivetrains can only deliver these benefits under quite specific driving conditions. To understand why, it is necessary to understand the fundamentals of why and how hybrids can improve efficiency.
Ignoring engine fuel types for a moment, there are two basic types of hybrid system, series and parallel. Series hybrids do not have a conventional gearbox: the engine drives an electrical generator directly. This generator in turn charges a battery pack, which then provides electrical power to a motor, or motors, which then drive the wheels. One key benefit of a series hybrid is that its internal combustion engine can be optimised to run at one or more specific constant speeds selected to give optimum fuel economy. The battery pack is also charged from regenerative braking – using energy which would otherwise be lost as heat from the brakes when they are used.
Series hybrids do however tend to take up more space than parallel systems, which is why most car hybrid systems are parallel systems, which is where the internal combustion engine drives into a normal automatic transmission in the conventional way, but then has an electric motor in parallel with the auto box to provide additional power to the wheels when required, or indeed to enable the vehicle to run on electric power alone. Regenerative braking is the only source of electrical power for the battery pack, unlike a series hybrid.
Unless a vehicle with a parallel hybrid system does lots of braking, therefore, it is unlikely to be more economical than a conventional vehicle; indeed it could even be worse as it needs to carry around the extra weight & drag of the hybrid electrics. What does this mean in real terms? Effectively, it means that hybrids come into their own in more urban duties rather than motorway blasts – I wince whenever I see a Toyota Prius bombing down the outside lane of a motorway, usually with their driver blissfully unaware that they could be saving loads of fuel if they were driving a conventional car!
It’s not always the hybrid driver’s fault though, because vehicle manufacturers, or for that matter the media, rarely make the significance of the type of roads or operating duty on which the car is driven clear. Full marks to Range Rover therefore for aiming the optimum usage of their newly-launched hybrid at primarily A & B road usage. In ideal conditions, the Range Rover Hybrid produces up to16% lower CO2 emissions & 17% better combined fuel consumption than the equivalent conventional model equipped with the same 3 litre SDV6 diesel engine and ZF 8HP70 transmission.
Even more impressive is that these gains have been achieved with no noticeable compromise to the passenger and luggage space inside the vehicle, in marked contrast to some earlier hybrid offerings from the worlds’ motor industry. This feat of packaging has been achieved because the new Range Rovers Premium Lightweight Architecture (PLA) structure was designed from the outset to accommodate a hybrid drivetrain as well as conventional systems. Thus the battery pack, for example is positioned very low down under the vehicle, although robustly protected from off-road damage.
As well as minimising any loss of interior space, this location ensures that the centre of gravity – a vital consideration for a vehicle with extreme off-road capability – it kept as low as possible. Indeed, the outward signs that this is indeed a hybrid are minimal, and as far as I could see limited to very discreet badges on the lower edge of each front wing and on the tailgate.Not only has the hybrid hardware been integrated into the vehicle without compromising interior space, even to the extent that a full size spare wheel is retained, the weight penalty has been kept to around 100kgs or so.
One area of concern regularly voiced in connection with hybrids is the potentially limited battery life. Range Rover have no qualms about including the batteries within their normal 3 year warranty, although they anticipate that battery life of the lithium-ion units fitted could in fact well be around 10 years. From personal experience with lithium ion batteries in hybrid buses this seems entirely reasonable: to date the first bus batteries have lasted some 7 years without issues.
As Colin Wells, Range Rover Hybrid Product Manager explained, Range Rover have opted to offer four driving modes for the vehicle. Firstly, EV mode, where it is capable of operating for up to 2 miles on electrical power alone. Range Rover see this “stealth” mode as being ideal for the early riser, who does not want to waken the neighbourhood as they set off. Secondly, a general or normal mode, where the battery pack is recharged by regenerative braking and the electric motor provides propulsion rather than the diesel engine whenever adequate battery capacity is available.
It is envisaged that this will be the normal operating mode for most conditions. Thirdly, Sport mode, where both diesel and electric power are used simultaneously to give the best possible performance. Finally, diesel only mode, where the batteries are charged at every opportunity and then held at the highest possible charge, in readiness for the driver to select a period of electric-only running.
It was critical that in offering the hybrid, the legendary off-road ability of the Range Rover was not compromised, and following extensive development to ensure that off road capability was the equal of a conventional Range Rover, such was the confidence of the company that to demonstrate these capabilities, three Range Rover Hybrids embarked on August 22 this year on an epic 16,000 km “Silk Road” trip from the home of the Range Rover brand in Solihull to the home of the parent company Tata, in Mumbai, India, successfully traversing 13 countries in 53 days.
Negotiating tracks so sticky with mud that they were impassable to other types of vehicle, the Range Rover’s hybrid engine combination – with a 35kW electric motor supporting the TDV6 3.0 litre turbo-diesel engine – returned excellent fuel consumption for a vehicle so spacious and powerful. Throughout the epic journey the Range Rover Hybrids typically returned 36 to 37 mpg.
Land Rover development engineers closely monitored data loggers fitted to each car, sending back more than 300 gigabytes of detailed technical records to their engineering team at Gaydon in the UK. The purpose of the expedition was not to test the reliability of mechanical components, which were already proven, but to fine-tune the calibration of engine and transmission software to ensure perfectly seamless performance in all terrains and extreme temperatures and altitudes. Technical setbacks reflected the roughness of the road surfaces: 15 punctures among the expedition’s three Range Rover Hybrids and four support vehicles, four wheels damaged by deep potholes, and four windscreens cracked by stones thrown-up on loose surfaces.
So how does this ingeniously packaged vehicle drive? In short, were it not for the power meter which appears prominently in the impressive digital display in front of the driver where one would expect to find a rev counter, it looks & behaves just like a conventional Range Rover, the ride, handling & general driving experience of which has received so much praise that it need not be repeated here. Indeed, such is the refinement in normal operation that I had to open the window at times to assure myself that it was in fact at times running in electric mode without the diesel engine operating.
The only indication that it was a hybrid came after much investigation, when it eventually dawned on me that the stop-start system, as now fitted as standard to most Jaguar Land Rover products, was in fact delaying the restart of the vehicle for some seconds as it picked up speed after a stop, since the electric motor was providing the initial power to pull away. In an all too brief road test it was not possible to get a feeling for fuel consumption, although the average consumption as shown on the computer was increasing steadily over 30 mpg even making good use of the extra power from the combined diesel plus electrical drive – at legal speeds of course!
One measure of a good hybrid system is for the cut-in of regenerative braking to avoid being intrusive to the driver, and the Range Rover Hybrid is excellent in this respect, with the blending between regeneration and the disc brakes being absolutely undetectable, yet clearly effective, as seen by observing the battery charge gauge.
Downsides on the road? Frankly, the only one of note was the power meter, the needle of which tended to whizz merrily around the scale, from full-scale reading to zero and back again with every change in throttle opening. This was, in truth a bit irritating, since the eye was inevitably drawn to the needles’ movement due to its size and prominence, even though it did not then deliver up any information useful to the driver. However, I have to confess to not investigating the handbook to gain an understanding of the meters messages – although how many drivers do study their manuals that closely?
Range Rover has positioned the Hybrid very much at the top of the market as a premium product, and this has inevitably received some negative publicity of the “why bother” nature. However, having driven the vehicle and considered its benefits, if I were in the market for a premium SUV, the additional feel-good factor from owning such a vehicle with no worse an environmental impact than many a recent everyday saloon car would certainly ensure the Range Rover Hybrid was on my short list!
For further information click here: LAND ROVER
|CO2 emissions||169 g/km||196 g/km|
|Urban mpg||42.0 mpg||33.2 mpg|
|Extra Urban mpg||45.0 mpg||40.4 mpg|
|Combined mpg||44.1 mpg||37.7 mpg|
|Diesel engine power||292 bhp||292 bhp|
|Electric motor power||46 bhp||n/a|
|Combined power||338 bhp||n/a|
|Combined torque||700 Nm||n/a|