Toyota Prius

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2004 Toyota Prius

Toyota Prius
Production:1997 – present
Class:Economy car
Body Styles:5-door hatchback '04–
4-door sedan '97–'03
Engines:Gas:Hybrid Synergy Drive – 1.5L I4 DOHC 16 valve
Electric:500V 50 kW motor
Length:4450 mm (175.33 in)
Width:1725 mm (67.97 in)
Height:1490 mm (58.71 in)
Curb weight:1325 kg (2921 lb)
Also known as:Toyota Hybrid
Shares components with:none
Similar models:Honda Civic Hybrid
Honda Insight
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2003 Toyota Prius

This article is part of the automobile series.

The Toyota Prius is one of the world's first commercially mass-produced hybrid automobiles. Manufactured by Toyota, the Prius first went on sale in Japan in 1997. The car was introduced to the worldwide market in 2000 and almost 160,000 units had been produced for sale in Japan, Europe, and North America as of the end of 2003. In Latin, prius means "ahead". The Prius (2000–2003 model years) is certified as a Super Ultra Low Emission Vehicle (SULEV) by the California Air Resources Board (CARB). The 2004 model is certified as an Advanced Technology Partial Zero Emission Vehicle (AT-PZEV), which means it earns PZEV credits, as opposed to it being a Zero Emissions vehicle part of the time.

The car was voted 2005 European Car of the Year, after the fuel-sipping sedan picked up the corresponding Motor Trend Car of the Year title for 2004. The Prius won the North American Car of the Year award for 2004 and was nominated in 2001.


How it works

The Prius has been called a true hybrid vehicle, designed from the bottom up. Toyota's goal for the Prius is to reduce the amount of emissions it produces and to be as energy-efficient as possible. They used several methods to try to achieve this goal, including:

  1. More efficient use of the internal combustion engine (ICE) and electric motors, reducing gasoline consumption. The Prius uses the more efficient Atkinson Cycle engine instead of the more common Otto Cycle;
  2. Two electric motor/generators, providing 67 hp (50 kW) @ 1200–1540 rpm and 295 ftlbf (111 Nm) torque from 0–1200 rpm, which significantly contribute to performance & economy.
  3. 50 kW IGBT inverter controlled by a 32 bit microprocessor, which efficiently converts power between the batteries and the motor/generators.
  4. Lower coefficient of drag at 0.29 (0.26 for 2004 model), reducing air resistance especially at higher speeds;
  5. Lower rolling-resistance tires, reducing road friction;
  6. Regenerative braking, a process for recovering kinetic energy when braking or traveling down a slope and storing it as electrical energy in the traction battery for later use while reducing wear and tear on the brake pads;
  7. Sealed 168 cell nickel metal hydride (NiMH) battery providing 201.6 volts;
  8. Continuously variable transmission -- the Prius does not use a typical CVT; Toyota calls it the Power Split Device ( The electric motors and gas engine are connected to a planetary gear set which is always engaged, and there is no shifting.
  9. Flexible resin gas tank, reducing the amount of hydrocarbon emissions in the form of escaped gasoline vapor.

Touted advantages of the Prius over previous energy-efficient designs include never needing to be plugged in, as all power is ultimately delivered from the gasoline engine. This means it drives like a traditional ICE automobile, with the onboard computer taking care of shifting power to and from the engine and motors, and automatically determining when to charge the battery, as well as the most efficient use of the engine or the electric motors (or both) based on driving conditions. This also means that one can not choose to use electricity from other sources to power this vehicle; some consider this to be serious disadvantage.

The engine is permitted to shut down once it has warmed up and the catalytic converter in the exhaust system has reached operating temperature. Once this occurs, the Prius can be driven on electric power only; this is sometimes referred to as "stealth mode" due to the lack of engine noise. This further reduces gasoline consumption and wear and tear on the engine. When driving conditions demand additional power from the engine, it is designed to start up automatically.

Frequent starting up and shutting down of the engine should not cause additional wear and tear nor emission problems, as in conventional automobiles, because the drive motors have enough power to quickly and smoothly spin the engine to optimal rpm (around 1,000) before the engine actually begins to "fire up". This avoids wear when the engine is "running" (with fuel and spark) at very low RPM, as happens in most vehicles.

The Prius gets better fuel efficiency in the city because the batteries get used more, whereas on the highway, the engine is used in order to recharge the batteries, and the wind resistance is higher.

2004 Prius

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Hybrid Synergy Drive
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HSD high voltage unit
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A battery module used on the Prius

The Prius 2004 model year is a complete redesign of the previous generations of Prius. The first generation (1997–2003) could not run its air conditioning unless the motor was running. In contrast, the 2004 model uses an all electric heat pump for heating and cooling. This allows more extensive use of the "stealth mode" (operation on electric motor only).

The new drag coefficient of 0.26 is the lowest in the industry.

The new (third generation) Hybrid Synergy Drive (HSD) replaces the earlier Toyota Hybrid System (THS) technology.

The 2004 Prius is a midsize car with more room than the previous compact and is a five door model (4 doors plus a rear hatch). In general the car is conveniently narrow on the outside, rather flat sided, and relatively tall (several inches taller than a Camry). The profile is much more continuous, with a short sloping nose transitioning to a highly sloped windshield and an arcing roofline ending in a cut-off Kammback. The additional height allows a more erect seating position and a higher eye point, giving a better view of the road to the driver. There is also a surprising amount of rear seat leg room, resembling that available in a much larger vehicle. Fold down rear seats with a 60/40 split make for easy carriage of most parcels.

With a smaller and lower voltage NiMH battery and an inverter to step the voltage up to 500V, the new model is more powerful (2 seconds faster in 0 to 96 km/h acceleration) and is 15% more fuel efficient than the previous generation Prius, with 60 mpg (4.7 L/100km) city and 51 mpg (5.5 L/100km) highway (according to the EPA). As the EPA city test is more consistent with downtown Manhattan than it is with most suburban driving, your mileage may vary. When driven appropriately, commuting and mixed suburban drivers are reporting realistic mileages of 45 to 50 mpg (6.3 to 5.7 L/100km). See also [1] (

The display shows mileage bars for each five minute segment of driving and this can encourage economical driving. The display also indicates instantaneous milage, which is useful for detecting when the vehicle has switched from electric-only to electric plus ICE. At this time it can usually be advantageous to accelerate rather than lug the vehicle, in an attempt to get to a more favorable location or speed range for electric-only mode.

The vehicle is classified as a SULEV (Super Ultra Low Emissions Vehicle), 90% cleaner than conventional gasoline-only automobiles. It comes with an Advanced Technology Partial Zero Emission Vehicle (AT-PZEV) certification by CARB (California Air Resources Board).

As an interesting side note, a $2,200 option package offered in Japan for the 2004 model gives it the ability to perform parallel parking by the on-board computer. Eighty percent of the Prius buyers in Japan have chosen this option. The system is not intelligent, though, so it is very limited. [2] (

When the vehicle is started it will operate for seven seconds before starting the engine. This can allow you to remove the vehicle from a garage before starting and so reduce the pollution in the house. Unfortunately it is much too quick to start the engine in most cases, as in some locations a complete downslope trip could be made without starting the ICE engine - actually putting energy into the battery. The Asian and European version of this vehicle provide a button labelled "EV" that maintains stealth mode after startup under most low load conditions. The US model has a nonfunctional blank button, although it is supported internally by the computer. While some have speculated that it was not been included in the interest of retaining the warranted battery life (100,000 miles in US 150,000 in California and several other states), engineers who note that EV mode is automatically overridden when the battery is only partially depleted have disputed that. In addition to information at online discussion groups, the PRIUS+ Project ( offers instructions for do-it-yourselfers who wish to enable the button, and aftermarket components provider Coastal Electronic Technologies ( offers a kit.

Evolving from the button project, The California Cars Initiative ( converted a Prius in 2004, adding larger batteries, and private companies EDrive Systems ( in the USA and Amberjac Projects ( in the UK announced plans to sell conversion kits in 2006. CalCars initiated efforts to promote fleet purchases of plug-in hybrids to be built by automakers, and documented the emissions benefits of plug-in hybrids not only on California's clean power grid but also on the national (50% coal-fueled) power grid.

A driving trick: Often you will pull up at a stop light that has just changed. In some suburban areas this may entail a wait of several minutes, as the lights cycle through various simultaneous or sequential left turns, cross traffic, pedestrians, etc. If the gasoline engine is running when you approached the stop it will take the better part of a minute before the computer recognizes the situation and shuts off the engine. There is a trick to getting the engine to shut off promptly. If you approached the stop in B (engine assist braking), you may then when stopped with the brake on, command N (neutral), then D (drive) - the engine will stop immediately - at least in 2004 US versions.

Passengers of the Prius can use their Bluetooth-enabled cellphone via the car's audio system without taking the phone out of their pocket. It is the first car released with this feature.


The first Prius model, NHW10, was sold only in Japan though personal imports have been made to Europe and Australia. Subsequent versions have seen wider sales, increased power and reduced battery weight.

FeatureModel Code
Body Style 4 Door
4 Door
5 Door
First Sales 199720002003
Battery Modules403828
Cells per module666
Total cells240228168
Volts per cell1.21.21.2
Total volts288273.6201.6
Capacity Amp hours6.56.56.6
Weight kg575045
Power kW435257
Max rpm400045005000
Power kW303350

Notable facts

  • 2005 European Car of the Year (Toyota Prius 2nd generation with 406 points, ahead of Citroen C4 with 267 points and Ford Focus II with 228) [3] (
  • Motor Trend Car of the Year 2004 (January 2004 issue)
  • Car and Driver magazine's Ten Best list for 2004.
  • Drivers of the Toyota Prius, or other Hybrid-Engine automobiles are allowed to drive by themselves in Carpool (High Occupancy Vehicle) lanes in some US states such as Virginia, California (pending) and Florida (requires $5 per year decal).
  • Los Angeles and San Jose, California allow free parking at meters for hybrid vehicles, including the Prius.
  • Due to the success of both the engineering and sales of the Prius, in 2005, Toyota plans to release a hybrid V-6 engine for the Lexus RX400h, as well as a hybrid engine version of the Highlander.
  • Toyota is also actively developing a hydrogen-fuel-cell engine. They have already successfully developed a RAV4 that can achieve 900 miles (1450 km) on one tank of hydrogen.
  • The fuel tank holds 11.9 gallons (45 L), although the internal bladder in American models limits the fill, giving a range of up to 600 miles (1,000 km).
  • In August 2004, Toyota began a Special Service Campaign (SSC 40G), affecting most previous generation Prius cars manufactured between 2001 and mid-2003. This repair involves re-sealing terminals on the high-voltage battery to avoid minor electrolyte leakage. Repairs will be performed free of charge on affected automobiles.
  • Starting with the 2004 model, Toyota is now producing the Prius on a standard mass production assembly line, resulting in one being produced every minute instead of one every 8 to 10 minutes. The use of a standard assembly line has dropped the manufacturing cost significantly, allowing Toyota to deliver a substantially upgraded model, which in turn has generated publicity and popularity. The limiting factor in Prius (and Lexus RX400h) production now appears to be third party component availability, particularly batteries.
  • The battery pack of the 2004 Prius is guaranteed for 100,000 miles (160,000 km) or 8 years, although Toyota has stated that they expect it to last 15 years. The warranty is extended to 150,000 miles (240,000 km) or 10 years for Prius in California and several other states that adopted the Californian emission control standards.
  • In May 2005, Finnish anti-virus firm F-Secure Corp. has tested a Prius for Bluetooth vulnerabilities in the on-board mobile telephony and computer systems and found the car has performed admirably. (
  • On June 1, 2005, the National Highway Traffic Safety Administration of the US started an investigation on the 33 reported cases of engine stalling when the Prius travels at highway speed. The cars were still operatable under battery power with substantial loss of power when the internal combustion engine failed to run. Toyota believes it was due to a computer programming error that was fixed in a recall (SSC-40D) issued back in September, 2004. The investigation needs to verify if all the reported cases occured to the cars that didn't receive the software fix. Some supporters argued that 33 cases among 75000+ cars sold was not an alarming figure. Besides, the Prius is safer than any other car with a failed engine, the Prius can still run with its electric motor until it can stop at a safe location.


Other hybrid-engine vehicles

  • Honda Civic Hybrid, another car which works similarly, but never runs exclusively on electricity.
  • Honda Insight, a 2-seat, manual transmission hybrid car which the EPA claims gets 60 miles per US gallon in the city, 66 mpg highway (3.92 litres per 100 km city, 3.56 L/100km highway ), also cannot be driven without the gasoline engine.
  • 2005 Honda Accord Hybrid, a hybrid based on the popular Accord Sedan; cannot be driven without the gasoline engine.
  • Ford Motor Company has released the 2005 Ford Escape Hybrid SUV. Toyota and Ford entered into a licensing agreement in March 2004 allowing Ford to use 20 patents from Toyota related to hybrid technology, although Ford's engine was independently designed and built. In exchange for the hybrid licences, Ford licensed patents involving their European diesel engines to Toyota.
  • The 2007 Nissan Altima has been announced. Nissan are not only licensing but also sourcing hybrid engine parts from Toyota for this vehicle.

See also

External links

fr:Toyota Prius id:Toyota Prius ja:トヨタ・プリウス nl:Toyota Prius pl:Toyota Prius


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