Toyoa Prius

January 21, 2005

Toyota Prius

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. Since then, there have been over 120,000 units sold in Japan, Europe, and North America as of September 2003. 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).

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 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:

-» 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;

-» Two electric motors, providing 67 hp (50 kW) @ 1200–1540 rpm and 295 lb-ft (111 Nm) torque from 0–1200 rpm. which significantly contribute to performance & economy.

-» Lower coefficient of drag at 0.29 (0.26 for 2004 model), reducing air resistance especially at higher speeds;

-» Lower rolling-resistance tires, reducing road friction;

-» 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 (a rechargeable nickel metal hydride (NiMH) battery) for later use while reducing wear and tear on the brake pads;

-» Continuously variable transmission. The Prius does not use a typical CVT, Toyota calls it the Power Split Device (1). The electric motors and gas engine are connected to planetary gear set which is always engaged, there is no shifting.

-» 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, all power being delivered ultimately from the gasoline engine. This means it drives like a traditional ICE automobile, the onboard computer in the Prius taking care of shifting power to and from the engine and motors, automatically determining the most efficient use of the engine or the electric motors (or both) based on driving conditions, and when to charge the Battery.

The engine is permitted to shut down once the engine 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, 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.

(1) ver (http://home.earthlink.net/~graham1/MyToyot...SplitDevice.htm)

2004 Prius

The Prius 2004 model year is a complete redesign of the previous generations of Prius. The first generation (1997–2003) Prius was based on the compact Echo and could not run its air conditioning unless the motor was running. In contrast, the 2004 model is specifically designed for this application and 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.

Hybrid Synergy Drive on a 2004 Toyota Prius.

The left side (black) is a 1.5 liter Internal Combusion Engine which both drives the wheels and the electric generator. The right side (silver) is the Toyota Hybrid Synergy Drive.

The new 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 Kammbak. 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 but higher voltage NiMH Battery 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 city and 51 mpg highway (according to the EPA). As the EPA city test is more consistent with downtown Manhattan then it is with most suburban driving, your milage may vary. When driven appropriately, commuting and mixed suburban drivers are reporting realistic mileages of 45 to 50 mpg.

The display shows mileage bars for each five minute segment of driving and this can encourage economical driving. It would be useful to have these even in gas guzzlers as they increase a driver's awareness of the effect of technique on mileage. 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 Japanese 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. It is likely that this has not been included in the interest of retaining the warranted battery life, for misuse of the button could certainly shorten that. As the battery is an integral part of the drivetrain, and that is warranted for low smog performance, up to 150,000 miles in California, these could be good reasons for not providing the button. In addition to information at online discussion groups, the PRIUS+ Project (http://www.priusplus.org) offers Instructions (http://www.calcars.org/prius-evbutton-install.pdf) for do-it-yourselfers who wish to enable the button, and aftermarket components provider Coastal Electronic Technologies (http://www.coastaletech.com/) offers a kit.

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 (energy recovery 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.

(2) ver (http://www.cnn.com/2004/TECH/ptech/01/15/c...k.ap/index.html)

Notable facts

-» Car of the Year 2005 (Toyota Prius 2nd generation with 406 points, ahead of Citroen C4 with 267 points and Ford Focus II with 228)

-» 2005 European Car of the Year

-» 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 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.

In http://en.wikipedia.org/wiki/Toyota_Prius

Prius 2000

Prius 2004