As an ultra fuel efficient vehicle the a fundamental requirement of the Prius design is an efficient aerodynamic form. The success achieved in this regard can be measured by the low 0.26 drag co-efficient.
This is achieved by the aero-efficient tear-drop body shape of the Prius and the improvements in air flow offered by aerodynamic aids placed in front of the wheels and a full underfloor cover to clean up the air flow under the car and reduce drag. A rear spoiler adds a finishing touch to clean up the air at the rear of the car.
Aside from the drivetrain, the other significant contributor to fuel usage is weight and here Toyota engineers have followed an aggressive weight saving regimen to reduce mass in any area possible without compromising the integrity or comfort of the vehicle. To this end a number of major body panels and some cast components are made from aluminium.
The advanced drivetrain with its Atkinson cycle engine, high speed electric motor/generator, planetary gear final drive and regenerative braking system provide the third element of the fuel savings exhibited by the Prius. This Toyota Hybrid Synergy Drive system has the unique ability to route energy to and from the various components in virtually any combination to ensure optimised performance at all times.
The interior of the Prius and its features list match the design requirement of providing a vehicle that meets advanced fuel saving and emissions requirements but matches contemporary expectations. The first impression that the driver will have on entering the Prius is one of relative simplicity.
There is no floor mounted gear shift, no hand brake lever on the floor and no apparent instrumentation other than a dark void immediately under the windscreen. An electronic key is provided to bring the vehicle to life and disengage the electronic steering lock.
Press the brake pedal and then the "Power" button, and the Prius immediately comes to life as the virtual image display instruments light up. A brief systems check is followed by the illumination of a "READY" light. At this time the dashboard mounted shift lever is used to select the desired direction of travel and pressing the accelerator will set the vehicle in motion.
The electronic shift lever provides for the selection of the desired range through a shift-by-wire system with a spring-loaded momentary action that returns it to a central position once the selection has been made.
Shift options are: Neutral; Drive; Reverse, and "B", an alternative driving range that offers a more aggressive regenerative power function. If an inappropriate selection is made the system will reject the selection and sound a warning.
Engine not running
Not too different from a run-of-the-mill automatic you might think, with one exception - there is no engine running at this time. Even when the accelerator is depressed this action is met with a mute response if in drive mode. In reverse a beeper will sound to alert the driver that reverse is selected.
The Prius uses stored electrical energy for initial acceleration up to 45 km/h at which point the hybrid drive system will seamlessly add the petrol engine element to the drive. No sign of engine cranking, not a hesitation or a stutter of any kind.
From this point on the Prius will perform like any other vehicle in the compact sedan class as the vehicle?s computer controls distribute and collect energy in the most efficient manner possible but without impeding performance.
If the EMV (Electro Multi Vision) display is set to the corresponding page a fascinating graphic indication of the flow of power between the various drive elements will be available. This touch screen system with button pre-selects for main function selection provides control for the audio system, climate control, and vehicle information system.
An interrupt screen is also provided to alert the driver of any system malfunction. If an abnormal condition is detected this screen will override the selected screen with a flashing warning to identify the area in which the abnormality has been detected.
Systems covered by this screen are: Electric Power Steering; HV (Hybrid Vehicle) battery warning - warning of a voltage drop in the hybrid battery; THS (Toyota Hybrid System) abnormality alert; HV immobiliser system abnormality warning ? when the shift lever is in "P" range, and a Shift-by-wire system warning.
This vehicle information element provides a mine of information via its page options. The energy monitor screen is perhaps the most fascinating with its continual display of the flow of energy between the Hybrid Synergy Drive system components. The current drive method (engine, motor, or both) is displayed, as is the power generation status of the engine and the regenerative braking system.
The fuel consumption screen indicates the average fuel consumption, the recovered energy accumulated, and the current fuel consumption. The average fuel consumption is calculated over a "last 5-minute" usage history. The recovered energy indicator reflects the energy recovered over a five-minute period.
The overall interior appointment level is in line with Toyota?s Camry GLi specification with some detail enhancements, particularly with regard to the air conditioning system fitted to the Prius. This system features a world first for mass production passenger vehicles with an electric inverter compressor system utilised.
The system employs an electric motor to exclusively power the compressor. This enables a stable air-conditioned environment to be achieved without using engine power. It is also independent of engine speed in its efficient delivery of cooled air.
The air conditioner is able to continually control air temperature and humidity even when the engine is stopped, as is often the case in an urban environment where the Prius is at its best.
Toyota engineers have focused on producing a high efficiency, low weight system that uses advanced controls to limit energy usage. The Prius team also had to consider the unique heating requirements of a hybrid vehicle where heated water from the engine cooling system would not always be in circulation if the system relied on the engine water pump.
To counter this an electric pump is fitted to ensure the continual supply of warmth to the cabin even when the engine is stopped.
A full auto setting automatically adjusts the air outlet temperature, blower speed, and vent direction in accordance with the selected interior temperature.
The interior temperature sensor is able to detect humidity as well and assists in controlling this aspect of the Prius interior to ensure that a reasonable level of humidity is retained in to prevent discomfort associated with extremely dry air.
The air conditioner can be operated by the touch screen controls of the EMV display or via a set of steering wheel mounted satellite controls.
The Prius standard features list includes: Audio system with radio and 6-CD changer (activated by satellite controls on steering wheel or touch screen on EMV display); nine-speaker sound; power windows on all four doors with auto up and down on the driver?s window; electric power steering; cruise control; height adjustment for the driver's seat.
There's also remote central locking controlled by electronic smart key; anti- theft alarm system with intrusion detection and electronic transponder type key matching and courtesy light fade-in, fade-out; powered side mirrors; plush velour upholstery; foot operated parking brake; and 60/40 split folding rear seat configuration. Aluminium rims (16 inch) with wheel covers are fitted. Tyres are special low resistance type with the designation P195/55 R16.
Ample storage space is provided with three closed storage facilities in the dashboard area, an overhead spectacle storage area, and a centre console that features two main storage areas. The front door side pockets include a recess designed to accommodate a 500ml water or soft drink bottle.
Two cup holders are provided for the front and rear within the central console. An auxiliary 12 volt power point is also provided in the central console. A tonneau cover is provided to secure the luggage compartment and an underfloor storage compartment in the boot provides a secure stowage area.
As a completely new platform within the Toyota vehicle range, the Prius was targeted to provide the highest levels of passive safety. To this end the body structure is based on an efficient crash impact absorbing structure.
Materials of different thickness are employed in the front side members to assist in absorbing and channelling impact energy away from the passenger cell. Strategically placed reinforcing elements are also designed to protect occupants by dispersing impact energy through the body structure.
Cowl and door "belt-line" reinforcements add further strength to the cabin in vulnerable areas and assist in reducing cabin deformation in a crash. A tibia pad is provided to minimise injury to the lower body area of the driver and front seat passenger. An energy absorbing structure is fitted behind the interior garnish at head and shoulder level on side structural members.
When impacted this element collapses and acts as a cushion to limit injury. Air bag protection includes frontal and side protection SRS airbags for front seat occupants as well as full length curtain side airbags.
The Prius engineering team went further than protecting just the occupants of the Prius from injury by incorporating a number of design features that will assist in minimising injuries to pedestrians.
A larger than normal clearance between the bonnet and the engine and drive components provides an effective energy absorber to lessen head injuries in the event of a pedestrian accident. The inner shape of the bonnet is also designed to limit this type of injury.
An impact absorber is fitted to the front bumper to help minimise leg injuries in a pedestrian accident. The placement of the windscreen wipers has also been optimised to limit injuries to the head and face areas in the event of a severe pedestrian accident.
This extensive list of safety features and their performance in European NCAP tests has resulted in the Prius achieving NCAP 5-star status.
Toyota has specified its ECB2 (Electronically Controlled Brakes) system for the Prius. This system features regenerative braking, VSC (Vehicle Stability Control) and EBD (Electronic Brake force Distribution).
The ECB2 system controls the four-wheel independent action of the hydraulic brakes, VSC, brake assist and ABS with EBD in accordance with the vehicle's operating conditions. Hydraulic brakes and the regenerative brake, which uses the HV system motor for its braking force, are applied in response to the driver's brake inputs.
The ECB2 system controls the blending of the regenerative and hydraulic elements to use the regenerative brake efficiently and optimise fuel economy.
A power backup unit is included as a supplemental power source to ensure an uninterrupted supply of power to the braking system in emergency situations.
This system uses a capacitor to feed power to the braking system in the event that the vehicle power supply goes down. The capacitor draws its charge from the vehicle power system and discharges when the ignition switch is turned off.
Toyota's Prius brings the future to reality in an elegant eco-friendly solution that provides an exceptional balance between energy efficiency, performance, interior space, features, and safety.
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