Integrated Electric Rear Axle Drive : provides electric drive alone at low speed, plus improved 4x4 ability in tough conditions
Integrated Electric Rear Axle Drive – used in conjunction with the ISG Integrated Starter-Generator system (as described below) - improves both urban emissions and off-road ability.
Land Rover’s unique electric drive is different from the hybrid technology used by some 4x4 rivals. They use electric drive only to the rear axle, significantly reducing off-road capability. Integrated Electric Rear Axle Drive enhances off-road performance by augmenting rather than replacing the mechanical drive.
Off-road, the Integrated Electric Rear Axle Drive system can provide additional torque, as required. And because electric power can offer maximum torque from standstill, it is most effective from virtually zero mph/kph. This offers better low-speed control and enhanced pull-away in difficult situations – such as on slippery surfaces or when towing.
On-road, the additional low-speed torque input from the Integrated Electric Rear Axle Drive offers multiple advantages. It allows electric-powered 'traffic creep' and low-speed acceleration up to 20mph or 32kph, without restarting the engine, benefiting fuel consumption and CO2 emissions. Whenever required, the ISG system restarts the engine, and the vehicle is then propelled by a combination of electrical and conventional engine power. The combined effect of delaying the restarting of the engine plus the continued assistance of electric drive, significantly reduces fuel consumption.
When quicker acceleration is required, the engine can be restarted immediately, so both the conventional engine and the Integrated Electric Rear Axle Drive system supply power from rest. In this case, the electric torque boost provided by the Integrated Electric Rear Axle Drive significantly improves acceleration without adversely affecting either fuel consumption or CO2 emissions.
The additional low-speed electric torque boost not only gives extra off-road ability, it also improves efficiency by using stored energy from the additional high-voltage battery system. Completely separate from the normal 12-volt battery system, this is a high capacity lithium-ion battery pack which is charged by regenerative braking energy.
The regenerative braking puts otherwise wasted braking energy back into the high-voltage storage battery system. When slowing the vehicle, pressing the brake pedal causes the driveshafts and propshaft to transfer energy from the wheels to the Integrated Electric Rear Axle Drive system, decelerating the vehicle and transferring the 'braking' energy to the storage battery. For harder braking and for emergency stops, the conventional braking system is retained and fully operational, working in conjunction with the regenerative braking function.
ISG Integrated Starter-Generator system improves emissions in traffic
One of the simplest yet most effective CO2 -reducing features highlighted on the Land_e is the ISG Integrated Starter-Generator. The ISG package replaces the conventional alternator and continues to take its drive from the normal ancillary belt. It is a ‘micro-hybrid’ system that allows the engine to be stopped automatically whenever the vehicle stops, as in traffic, and under the control of the ECU it restarts the engine quickly and smoothly when required. The engine does not idle unnecessarily when the vehicle is stationary, to the further benefit of both fuel economy and CO2 emissions.
Together the engine stop-start function of ISG, plus the regenerative braking function, provided by the Integrated Electric Rear Axle Drive offer the potential of a 20 per cent reduction in CO2 emissions. The outstanding multi-terrain ability that is at the core of Land Rover is also enhanced.
Seamless re-connect is a system that significantly reduces fuel consumption by cutting mechanical losses. Drive to the rear wheels is automatically disconnected when conditions allow, such as cruising on a dry surface. Yet unlike hybrid and selectable 4x4 systems, there is instant access to Land Rover’s full range of four-wheel drive abilities. The Propshaft with Seamless Re-connect allows the Propshaft and rear drive components to come to rest, avoiding unnecessary rotational losses.
When rear drive is required – when, for instance, the system detects slippery conditions – the system reconnects the rear axle automatically and virtually instantaneously. The system not only re-engages full 4x4 much faster than rivals, it also offers much better 4x4 capability when connected. Re-engaging drive seamlessly also has safety benefits. It does not affect the car’s dynamic balance in the same way as a slower and less progressive re-connection.
The technology also reinforces Land Rover’s fundamental principle to ‘Tread Lightly’. By ensuring that front and rear wheel speeds are correctly matched, and with the additional control of the Integrated Electric Rear Axle drive, the drive layout virtually eliminates wheel slippage, which in turn reduces soft-surface damage – for instance on grass.
The ISG Integrated Starter-Generator, Integrated Electric Rear Axle Drive and the Seamless Re-connect propshaft are fully compatible with all Land Rover engine and transmission options, and could be adapted for any model and any market.
Terrain Response e-Mode, for improved fuel economy in town
Land_e shows six Terrain Response modes:
The e-Mode is shown for the first time and focuses principally on on-road use. This configures all the vehicle’s e-terrain systems for optimised fuel economy. It always retains instantaneous access to Land Rover's four-wheel drive capability but adopts soft throttle responses, and delivers early shift points.
The other five modes are already available on some Land Rover products – General Driving; Sand; Mud and Ruts; Grass, Gravel and Snow; and Rock Crawl. In the Land_e, all use combinations of normal engine and Integrated Electric Rear Axle Drive. In all off-road modes, the engine is never shut down, even if the vehicle is stationary.
In Sand mode, primary power is supplied by the engine; the Integrated Electric Rear Axle Drive system monitors torque to detect either wheelspin or bogging-down, and intervenes as necessary, either to stop tyre slip or to provide additional torque to deal with soft, deep sand.
In Mud and Ruts mode, primary power is again supplied by the engine, while additional torque is available from the Integrated Electric Rear Axle Drive system for heavier mud or deeper ruts.
In Grass, Gravel and Snow mode, control is more important than power, so engine power is fed in only once the vehicle is underway. Integrated Electric Rear Axle Drive is used for driving away without wheelspin even on very slippery surfaces – by constantly monitoring torque and intervening rapidly to prevent tyre slip. In this mode, the Integrated Electric Rear Axle Drive can respond to wheelspin even more quickly than the engine management, and can cancel the initial slippage within one-eighth of a wheel rotation – a critical figure that is small enough to regain grip and prevent permanent damage even on wet grass. No other system achieves this.
In Rock Crawl mode, speeds are typically below 5mph/8kph. Integrated Electric Rear Axle Drive now provides the primary power source, boosted as necessary by normal engine torque. In all cases, the great advantage of Integrated Electric Rear Axle Drive is that an electric motor offers maximum torque at the lowest wheel speeds, for the ideal mix of power with control.
Bio-diesel moves towards a lower carbon fuel
An increasing emphasis on diesel power is clearly important to overall CO2 reductions, and bio-diesel capability extends the potential advantages. Bio-diesel is a fuel derived from renewable and sustainable sources, such as natural oils from soya beans or other easily cultivated vegetable or cereal crops. It is currently commercially available as a blend of bio-derived diesel and petroleum-derived diesel, in varying proportions, and bio-diesel offers reduced emissions compared with petroleum-derived diesel.
Currently, a five per cent bio-derived content is typical with forecourt diesel. Potentially, a vehicle could operate on a 25 per cent bio-diesel mix, which is a realistic goal within a few years, and one supported by the oil industry and governments. A vehicle running on 25 per cent bio-diesel mix could potentially reduce its CO2 emissions by up to 25 per cent. Next generation bio-fuels made from crop wastes are also being developed, and these will deliver even greater CO2 reductions, as well as being more sustainable.
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