|The new Freelander 2 TD4_e. Click to enlarge.|
Land Rover introduced the Freelander 2 TD4_e featuring a new Stop/Start system at the Paris Motor Show. The Freelander 2 TD4_e is Land Rover’s most fuel-efficient vehicle to date and is the first production vehicle to incorporate technologies from the company’s program of engineering initiatives collectively named e_Terrain Technologies (earlier post).
On the standard EU4 cycle, the CO2 emissions of the Freelander 2 TD4_e are reduced by 8% (15 g/km) compared with the outgoing manual diesel Freelander 2 TD4 (from 194 g/km to 179 g/km). Fuel consumption improves from 7.5 L/100km (31.4 mpg US) to 6.8 L/100km (34.4 mpg US). In additional tests, Land Rover engineers measured fuel savings approaching 20% in heavy urban traffic.
These gains, coupled with the added benefits of the gearshift indicator light, software developments and efficiencies from low-rolling-resistance tires, make the Freelander 2 TD4_e the most fuel-efficient production Land Rover yet built.
The Stop/Start Freelander 2 is the first production vehicle to benefit from the massive £700 million [US$966 million] investment in sustainable technologies by Jaguar and Land Rover. From mid-2009, the Stop/Start feature will be included as standard on all Freelander 2 TD4 manual models, with no associated increase in list prices.—Phil Popham, Land Rover’s managing director
Land Rover’s new Stop/Start system improves fuel efficiency in urban and stop-start driving. The vehicle automatically shuts down the engine in appropriate conditions. When the driver is ready to move off, the engine instantly re-starts. For the engine to shut down, the vehicle must be stationary, the gearbox in neutral and the clutch pedal raised. To re-start, the driver depresses the clutch and the enhanced starter motor engages the engine, ready for when first gear is selected.
The Stop/Start system is automatically activated each time the ignition is turned on, although there is a switch on to disable the system, if the driver so desires.
To reduce the engine shake associated with some diesel engines when stopping, the Freelander 2 TD4_e features controlled throttle closing and ramps down fuel in a smooth fashion, while the alternator is also turned off during the shut-down procedure, reducing load on the engine. A software feature change and revised engine calibration further aid smooth shut-off, while engine shake on start-up is reduced by the Freelander 2’s optimized engine-mounting strategy and inherent tuning.
The Stop/Start system. The engineering team developed a new heavy-duty starter motor, a new ring gear, a new dual mass flywheel friction control plate and an absorption glass mat battery for the system. The grease seals on the 2 kW starter motor have been enhanced significantly and new hard-wearing copper-tungsten contact material has been sourced and specified across the TD4_e range to enhance wear resistance within the starter solenoid.
An all-new ring gear is specified for all TD4_e models to cope with the increased frequency of starts. The ring gear is attached to the engine flywheel and comes into contact with the starter motor each time the engine is started. The new ring gear is manufactured from a harder grade of steel and contains more than 25% more carbon to improve durability.
Diesel-powered Freelanders with manual gearboxes have always featured a dual mass flywheel to ensure engine refinement at start, stop and low speeds. A new Polyetheretherketone friction control plate has been developed for the Freelander TD4_e. This is able to withstand seven times the pressure of the outgoing plate, to ensure greater levels of refinement under even greater start and stop demands.
New absorption glass mat technology has been developed, offering deeper discharge and recharge characteristics and reduces battery deterioration under much heavier usage. Fine glassfibre matting has been introduced to sit pressurised between the new absorption glass mat battery plates. This aids the battery’s longevity in two ways: by allowing the electrolyte to function normally under greater pressure and by providing mechanical support for the plates, reducing battery degradation.
A voltage quality supplies a constant voltage around the vehicle’s electronic components during a stop-start, ensuring that key services continue uninterrupted by the sudden outrush of amps from the battery. This technology is effectively a direct current converter, which can convert low voltages, such as that experienced during a stop, to a stable higher level for short but crucial boosts, ranging from one to five seconds in duration.
A battery monitoring system monitors the battery’s state of health to ensure that the Stop/Start feature functions reliably. The technology measures factors such as natural battery degradation, ambient temperature, charge and discharge activity and voltage, to make sure there is enough power available for an effective stop-start. If any of these factors show a low measurement, the Stop/Start feature is overridden and the engine will continue running until more battery power is available.
The Freelander 2’s brake system is specified with significant vacuum reserves, but these reserves can become depleted for a number of reasons, such as use of the brake pedal when the engine is switched off. Ultimately this would lead to vacuum reserves becoming exhausted, which would affect the brake servo’s operation and pedal loads, in some cases causing them to rise substantially.
To mitigate this, the brake vacuum sensor is specified on all Freelander 2 TD4_e models, and if vacuum reserves fall to a level that will affect brake pedal loads, the system overrides the Stop/Start function until the brake vacuum is replenished – ensuring brake pedal loads are maintained.
A number of changes have been made to the Freelander 2 TD4_e’s climate control system to help ensure occupant comfort and reduce misting during stop-start situations. One significant change is the introduction of an auxiliary water pump. On conventional vehicles, the water pump shuts down with the engine, but on TD4_e models, the introduction of the auxiliary water pump maintains the flow of coolant during engine shutdown, keeping a steady cabin temperature.
The climate control system monitors cabin temperature and maintains fan speed at a level that will protect the battery's state of charge when the engine is shut down. In extreme hot or cold conditions, extended stops, or if an occupant selects a higher fan speed during a stop, the engine will re-start if necessary to preserve occupant comfort.
Evaporator temperature, the factor that gives rise to screen misting, is also monitored and the enhanced climate control system will periodically cool the evaporator as necessary to mitigate misting during a stop-start. The system operates the windshield defrost shutter and, if the evaporator is wet, the shutter will remain closed for a few seconds after an engine restart until the vapour is dissipated, again mitigating windscreen misting.
Tata Motors acquired Land Rover and Jaguar from Ford earlier this year. (Earlier post.)