Toyota Prius sedan looks conventional but uses two engines
Bob Plunkett
Date Posted: 5/10/2005
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HOT SPRINGS, Ark. -- Cruising up Central Avenue in the spa city of Hot Springs, a four-door vehicle of compact dimensions darts through the traffic of so many tourists who flock to this resort in the pine-covered mountains of Arkansas.
None of the sightseers seems to notice that the perky little car moving up the avenue represents a revolutionary concept in vehicle propulsion and as such happens to be a rarity among all automobiles on American roads.
Instead, our car simply blends into the street scene, its roly-poly shell effectively concealing the radical nature of the mechanical systems that motivate it.
What makes this vehicle so unusual?
Well, anyone who pops the hood and peers into the engine compartment will find not one but two motors aboard. There's a thrifty but conventional 1.5-liter four-cylinder plant that operates on gasoline plus a battery-powered electric motor of permanent-magnet design.
A sophisticated computer device controls all energy produced by the two motors and applies it directly to the front wheels in infinitely variable measures.
Under light-load situations, such as start-up or moving in reverse, all power comes from the silent electric motor.
For normal driving, the 70 hp gasoline engine supplies primary thrust.
However, power from the gas engine is utilized in two different ways. One portion of this energy is used to turn the front wheels, while another portion powers an electric generator that runs the electric motor, which in turn sends supplemental power to the wheels.
Stomp the accelerator to speed into a passing lane and the electric motor continues to supplant the power, yet for such a heavy demand of power the operating energy comes directly from a bank of on-board batteries.
A regulator maintains a constant battery charge so no external recharging is needed. Internal recharging occurs either during braking, when the gas engine operates as a generator, or when the electric generator does the recharging job.
What's the point of such a complex powertrain?
It's to conserve carbon fuels and at the same time generate far fewer harmful greenhouse gases than the typical emissions of a conventional car.
This vehicle -- developed by Toyota and labeled as the Prius -- earns fuel economy figures as high as 52 miles per gallon in stop-and-go urban driving situations.
Further, it pares hydrocarbon and nitrous-oxide emissions dramatically and qualifies as a super-ultra low emission vehicle (SULEV), meaning that its emissions are 75 percent cleaner even than an ultra-low emission vehicle (ULEV) and 90 percent better than the LEV standard.
But the magic behind Toyota's design is that the Prius accomplishes these energy-conservation feats without resorting to radical sheetmetal schemes or by compromising space and comforts for the passengers who ride in the car.
It looks conventional and drives that way too, although in recent tests the Prius we piloted for more than 500 miles consumed less than ten gallons of regular-grade fuel.
During all of that drive time, we never noted a lack of muscle for quick accelerations or to keep pace with traffic on a freeway because there was always enough spark.
Also, we never worried about which engine was supplying the power or felt any loss of power in the transition from one motor to the other because power and energy management works automatically.
A video screen, centered high on the dashboard atop the central stack of audio and climate controls, illustrates operations of the energy management system with icons representing the gas engine, electric motor, drive wheels and battery. Colored arrows depict the energy flow, with a red arrow running from the gas engine or electric motor to the wheels when either plant supplies the power, or a green arrow flowing back to the electric motor and on to the battery when recharging occurs.
It's fun to observe the intricate dance of red and green arrows, although as driver you must be careful to keep eyes on the road instead of the video screen.
The only thing different you'd notice when steering the Prius is the position of the instrument panel. The digital display is mounted not directly in front of the steering wheel in the customary position but at the top center of the dash at the base of the windshield.
Backlighted icons indicate transmission gear selections, fuel level and odometer mileage plus digits showing vehicle speed.
And the transmission is an electric continuously variable device, so you don't feel the abrupt shift points of a conventional automatic, only a smooth power flow.
Toyota's designers borrowed spatial concepts for Prius from the Echo subcompact sedan with its tall structure. Rather than the typical long, low and slinky shape of a conventional car, the Prius stands tall in the aerodynamic format of a vertical bubble on wheels, seemingly tipped forward due to the high tail and low nose united by an arched roofline inset with a sharply raked windshield.
Inside, the cabin floor dips low so you can step aboard easily, and the ceiling bows high to fit tall chair-like seats. Passengers in the two front buckets sit upright, with their heads positioned higher than normal for better visibility though an expansive wrap of windows.
Still, ample air space remains overhead, which diminishes the crammed and jammed atmosphere of the typical small car.
Prius also contains a back bench seat that fits three, plus a rear trunk of reasonable scale.
Standard appointments include air conditioning, power windows and door locks, power mirrors and an audio kit with cassette deck and AM/FM stereo.
Safety gear ranges from a safety-cell structure to frontal air bags, quick-acting rack and pinion steering and brakes with anti-lock controls.
An independent front suspension adds MacPherson struts and L-beam lower control arms, while the rear torsion-beam axle conserves space to make room for the large trunk.
All of this complex technology as applied to Prius should load the bottom line yet Toyota brings Prius to market for $19,995.
In addition, up to $2,000 of the purchase price may qualify as a clean-fuel vehicle tax deduction.
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| 2001 TOYOTA PRIUS VEHICLE SPECIFICATIONS |
| Description: |
Compact hybrid sedan
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| Model Options: |
Compact hybrid sedan
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| Wheelbase: |
100.4 inches
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| Overall Length: |
169.6 inches
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| Engine Size: |
DOHC 1.5-L I4
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Magnet 33 kW Electric Motor
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| Transmission: |
Electric CVT
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| Drive: |
Front
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| Braking: |
Disc/drum/ABS
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| Airbags: |
2 (front)
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| Gas Mileage: |
52/45 mpg
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| MSRP Price: |
$ 19,995 |
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