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The Toyota Prius (2000), The successful blend of gasoline and electricity

By Larry Weitzman

Electric cars do not appear to be a viable alternative for the family sedan. Battery technology is limited by energy density, with gasoline have a 10 to 1 edge in energy density over batteries. Pure battery powered electric cars will always be limited in range to well under 100 miles and will take hours to be refueled, i.e., resupplied with electrons. But Toyota has a better idea. What if we combine the best of battery technology and with an extremely clean running conventional gasoline engine? The answer is a very high tech, high mileage four door sedan Toyota named the Prius with reasonably good performance.

That's exactly what the Prius does. But in doing so Toyota cleverly designed a power delivery system that seamlessly uses power from the electric motor in conjunction with the gas engine or solely the gas engine powering the wheels, while simultaneously charging the batteries or with solely the electric motor driving the front wheels. More on it's operation later.

The exterior design of the body appears to be dictated by the function of the Prius. It has some of the characteristics of the Echo, but it is better looking. The front end is very short and sloping. The steeply sloped hood is only about 28 inches long by 57 inches wide. Stuffed under that hood is a transverse mounted l.5L DOHC four cylinder engine and to the left is an electric motor system. In addition, somewhere in all that mass of hoses, wires, reservoir and metal objects is a transmission and the key to the system, a power splitter. The body is hard edged with and upper and lower ridge line giving needed definition. The window line is clean and pleasing with the rear deck also being very truncated. Take away the spoiler and the rear deck measures about 10 inches. Good looking tail lights finish off the clean design.

It is only 169.6 inches long on a very cab forward and long 100.4 inch wheel base. Width is 66.7 inches and height is a tall 57.6 inches. Because of the thick hip, cargo capacity is a generous 11.8 cubic feet.

Under that small front hood is the Toyota 1.5L four cylinder DOHC gasoline engine with VVT-i. It is unusual in that it puts out 70 hp at 4,500 rpm and 82 pounds of torque at 4,200 rpm in the Prius with an extremely high 13:1 compression ratio. In the Echo, this same power plant pumps out 108 hp @ 6,000 rpm with "only" 10.5:1 compression. Both vehicles run on 87 octane regular unleaded. VVT-i, which means variable valve timing with intelligence, gives the engine more flexibility, torque and better emissions through the more precise controlling of engine breathing. After all, an internal combustion engine is nothing more than an air pump, and being able to more efficiently control the breathing of that air pump will only make it more efficient and cleaner running.

But this gas engine has a "kicker" in the form of a permanent magnet 44 hp electric motor. All this power is available anywhere from 1,040 to 5,600 rpm. Torque is rated at 258 pounds at 0-400 rpm. This motor can operate independently of the gas unit. It is connected to the front wheels through and electronically controlled continuously variable transmission (CVT) and a power splitter. The electric motor gets the energy to drive from a generator driven by the gas engine or the small sealed nickel metal hydride battery pack located in the floor of the trunk between the rear wheel wells(it has an 8 year/100,000 mile warranty) which is recharged by the gas engine or the Prius regenerative braking system. With regenerative braking, the engine is off and the electric motor which is still connected to the drive wheels becomes a generator, converting the kinetic energy that would be lost to ordinary braking into a flow of electrons to recharge the batteries.

The CVT transmission is not new technology. It has been used in small automobiles manufactured in the Netherlands called the DAF and in a motor scooter from the 1940's and 50's called the Salisbury. It provides, though a series of belts and pulleys, an infinite number of gear ratios that provide the optimum in performance for given speed or power demand.

The CVT never shifts into a new planetary gear. Power delivery resembles a pre 1957 Buick Dynaflow, except it is a lot more responsive and faster than either a 1954 200 hp Buick Century or a 1955 188 hp Buick Special which ran 0-60 in 12.3 seconds and 13.5 seconds respectively. And that was using low gear before manually shifting into drive. If the Buicks were to start in drive, which was how they normally were driven, then the Prius would win an drag race even if you left the emergency brake on.

During several 0-60 runs, the Prius averaged 11.70 seconds, with a best run of 10.90. Passing was reasonable with 50-70 averaging 6.56 seconds, about average for most economy cars. Going up hill will slow that time to 12.56 seconds, again about average for its class. But the tranny gives the Prius maximum performance giving the sensation that acceleration improves with speed. It almost does as shown by its reasonably quick 60-80 sprint of 8.01 seconds only a second and a half slower than 50-70 mph.

In around town driving, the Prius shines with quick responsive acceleration. There is no lag time waiting for a downshift, the response is instantaneous, zipping the Prius from 20-40 mpg in what seems to be a second or two. It will satisfy the power hungry and the penny pinchers at the same time. But it will also make smog haters happy. The Prius is rated as a SULEV, or Super Ultra Low Emission Vehicle. That is 90 % cleaner than vehicles that are classified as an LEV and 75% cleaner than ULEV classification. The Prius is as close to a zero emitter as you can get and for all intents and purposes it is a zero emitter as electricity for ZEV cars comes from power plants. ZEVs do emit less relative to their power source, but with the SULEV technology, we are down to the very short strokes as to cleanliness.

But the driving experience is truly unique. Turning the ignition key may or may not start the gasoline engine. You have to be careful backing out of the garage. I almost ran over my dog laying hidden behind the Prius, as the Prius makes no noise without the gas engine running. Sadie got up in the nick to time and look at the car with a bewildered look, thinking that can't be happening with out the vroom-vroom noise. This is not a car to chase down the street. Sadie has since stuck to barking at the local wildlife and napping anywhere but behind cars. It just starts move in the direction desired. Initial response from the accelerator starts with the electric motor and if only low acceleration requirements are sensed by the computer the primay gas motor never starts. I could drive the Prius with light throttle pressure with the electric motor only at speeds up to about 35 mph. So in stop and go city driving, it is possible to use the electric system only. If the batteries get low, the gas engine will come alive and send electrons to the generator and the battery system. A dash mounted color LCD screen tells you what it going on in the power system, whether the gas motor is driving the wheels or the electric motor is doing the work, or whether it is a combination of both motors. It lets the driver know when regen braking is taking place and whether the gas motor is charging the batteries.

In normal driving, the gas engine comes on line instantaneously and both motors power the car, or sometimes the gas motor alone will power the car, the computer gets to decide.

The overall experience is incredible smoothness because of the electric motor.

But thinking that this is a commuter only would be incorrect. In a drive to San Francisco over the weekend, it was number one lane only. The Prius had no trouble keeping up with traffic with good response and plenty of pedal left over even at 70 mph plus (plus). I didn't do a top speed test, but cruising effortlessly at 80 mph will be no problem. Top speed, if not limited by electronic intervention should be 100 plus mph. There is no tach so engine rpm at speed is impossible to tell, but at any speed above 50 mph, the gas engine was on line. That is why the EPA ratings of 52 mpg city/45 mpg highway reported. In the city cycle, the gas engine isn't required, thereby boosting mileage. I am told that the battery range is about 10 -15 miles. So even if you were to run out of gas (never a good idea), you can count on the electric motor getting you to a gas station unless you are in the middle of the Mojave desert.

During one period of 133 miles, the Prius used only 2.77 gallons of fuel. That's 48 mpg and the Prius was driven hard, not easy. Getting good mileage wasn't the objective, it's just the result. My 1956 150 cc, 6 hp Lambretta motor scooter only returned about 70 mpg, and I got seriously wet during winter and fried during the summer. And top speed was about 55 mph flat out. Even of all the motortcycles that I have owned, my most economical was a 500cc Honda Four with 50 hp that averaged about 42-45 mpg. But it would definitely outperform the Prius with 0-60 times well below 6 seconds but had only natural air conditioning..

Braking is unique. Prius uses an electronic "brake-by-wire" system. Upon light brake application, the computer sends a signal to the regenerative braking system to slow the vehicle with generator braking. Further application of the brake pedal causes the front disc/rear drum set up to haul the Prius to a stop. ABS is standard. In panic stops from 40 mph, the Prius would stop between 42 to 45 feet. But they do feel different. In two different cars, the brakes felt the same so the braking feel can not be attributed to this particular sample. As pedal pressure is applied the stopping forces seem to increase without any additional pedal pressure. I felt this in other cars as well including the $70,000 plus Audi A8L. It takes a little getting use to, but after about a week, they feel normal. It is a quirk, and should not be characterized as a deficiency.

Underneath, the solid structure is suspended by MacPherson Struts up front with a torsion beam rear with shocks and coil springs in the rear. Antiroll bars at each end.. On Ponderosa Road, the ride is reasonably good with the suspension soaking up most of the washboard. In the two 90 degree bumpy corners, the Prius was a little twitchy at speed, but certainly nimble.

In the twisties of Green Valley and Airport Road, the Prius could handle the tightest corners at near maximum legal speed. But the Prius may be limited by the skinny 175/65X14 rubber on standard great looking multispoke alloys. The tires felt as if the sidewalls were rolling under during hard cornering. Steering was also a tad bit quick making it feel as if the Prius initially oversteers then succumbs to understeer. There is some body roll, but overall handling is good and after a week, it became throughly enjoyable in the twisties. On the highway, the quick steering required some acclimation, but it was accurate with maybe too quick on center feel, but excellent off center feel.

Prius was controllable at all times and on balance felt no difference than most other small economy cars, especially the Echo, which could be considered a distant cousin. Is it fun to drive? You bet. The uniqueness adds to the fun quotient, but its overall smoothness and quiet adds to the enjoyment. It absorbs bumps and freeway intrusions as good if not better than other small cars and that is good. It did especially well on large bumps.

The inside is comfortable and roomy, again taking a cue from the Echo, which has more room than it should have considering its dimunutive size. The front seats are covered in a thick soft, monotone gray fabric and are very comfortable with manual adjustments fore and aft and seat back rake. The dash is unusual with center instrumentation as in the Echo, with an LCD screen below containing radio functions and systems operation.

The rotary automatic AC controls are located below the radio controls which has a digital clock read out above where the cassette is inserted. But the station readout or operation is read on the LCD screen above.

Below the AC is a door for the optional CD or CD changer ($335/$550). The center console is narrow but deep and there are two cupholders in the front and two in the rear in the rear of the console.

The rear seat is very comfortable for two reasonably sized adults with generous leg and headroom. There is no fold down feature for expanding the trunk, maybe because of the battery pack, but notwithstanding the trunk is well shaped and seems larger than its claimed 11.8 cubic feet.

Pricing is very competitive. It is sold as a single line car with one trim level. Base prise is $19,995 plus $455 for the shipper. It is manufactured in Japan. There are only six options all under $115 except for the two CD options. The single play unit is $335 and the six pack is $550. Go for the six pack when ordering. The only items to go for are the $52 wheel locks (if you live outside of El Dorado County, just kidding) and the really neat embroidered floor mats for $70 with the green leaf. The cargo net is $45 and a glass breakage sensor is $115. The most this automobile can cost you is $21,482.

There is a demo model at Thompson's for customers to try (please give it up when your done) and the orders are placed be the dealer directly with the factory. Deliveries are now being scheduled for January and side impact air bags will be an option. There is a tax deduction for up to $2,000 as the Prius qualifies as a "qualified clean-fuel vehicle".

Maybe I was wrong, there just might be a place for electrons to help power automobiles. Toyota thinks it has the answer in a new Hybrid called the Prius, which uses gasoline and electrons or electrons by themselves to motivate this new car. The first drive made an immediate impression that this vehicle has a place in most everyone's garage. This car is slick.

First is the drive system. It has two motors or one engine and one motor. The engine is a 1.5L DOHC inline internal combustion four with 16 valves that puts out a modest 70 hp at a very low 4,500 rpm. The motor is a 44 hp electric with that kind of power generated from 1040-5,600 rpm and a stump pulling 258 pounds of torque between 0-400 rpm. With a unique devise called a power splitter, both motors can drive the front wheels with the electric motor being directly attached to the drive wheels and the gas engine using a gearless continuously variable transmission or CVT.

CVT's have been around for years and are used in a car manufactured in the Netherlands called the DAF. There was a motor scooter in the 1940's called a Salisbury that also used a CVT transmission. The technology is not new, but the application is. The electric motor is driven by a generator that is powered by the gas engine or by the small sealed nickel metal hydride battery pack located in the trunk. This is not an electric car that is powered by batteries alone. If that were the case, the range is about 10-15 miles.

The idea is to continuous charge the batteries and run the generator to power the electric motor with the gas engine when required and to use the electric motor only when conditions permit such as low speed city driving. The braking is regenerative and the performance is brisk, especially considering the EPA fuel economy ratings of 52/45 city/highway. 52 miles to the gallon of gasoline in the city cycle.

By brisk, Toyota estimates 0-60 in the 12 second range, but a couple of quick burst from 0-60 indicate that the estimate is very conservative. Passing tests will have to wait till a full report, but they should be adequate or better. Without a tranny shifting, acceleration seems to increase with speed. But it does so with uncanny smoothness and silence.

The interior is comfortable and roomy, especially for a car that is only 169.6 inches long riding on a 100.4 inch wheelbase. With is a nominal 66.7 inches with a height of 57.6 inches. The exterior appearance is dictated by interior efficiency. But the result is a design that is not unlike the Echo, with a little more of a hard edge look.

The dash is unconventional with a central speedo up on the dash and a LCD screen that tells you what's going on with the systems, fuel economy and the sound system. The AC system worked well in the 100 degree heat. Another unusual feature is the gear shifter. It's dash mounted with the indicator located with the speedo.

Suspension is by MacPherson struts up front and a torsion beam axle in the rear. The ride was extremely smooth and quiet. Handling was quick with decent feedback from the steering wheel. It is fun to drive.

The starting drill is turn the key. Nothing happens. Put it in gear and step on the gas (maybe a better name would be the electron accelerator) and the car with only the electric motor starts to move silently. Step on the go pedal a little more and the engine comes on almost unnoticed as the car moves away smartly, joining with the electric motor for direct power to the wheels and power for the generator and batteries. Back off the throttle at a 25-30 mph cruise down Broadway and Main Street and the engine (again almost unnoticed) gets silent and the car gets very smooth and extremely quiet. Go for a while and the engine comes back on line feeding power to the generator and batteries then off again.

Stopping will also silence the gas engine as the brakes do their regen job. You need to drive this car, it will surprise and amaze you. There is nothing else like it in a four door sedan that drives like every other good sub compact or sub compact except that it is much quieter and more frugal.

Toyota says that the car costs nearly $30,000 to build and sell, but they are selling copies for $20,000. I get it, they loose money on every deal, but make it up in volume. If production goes up, costs will go down, but this car is a real commitment to a new technology that has been proven by its use for three years in Japan.


Price                       $20,000

One 1.5L DOHC 16 valve      70 hp @ 4,500 rpm    
inline four                 82 lb-ft of torque @ 4,200 rpm

One permanent magnet        44 hp @ 1,040-5,600 rpm 
electric motor              258 lb-ft of torque @ 0-400 rpm

Continuous Variable with 
power splitter

transverse mounted, front wheel drive

Wheelbase            100.4 inches
Length               169.6 inches
Width                66.7   inches
Height               57.6   inches
Weight               2,765 Pounds
Fuel Capacity        11.9   gallons
Batteries            228 1.2V cells, sealed nickel-metal hydride

0-60                 12.0 seconds (estimate)
50-70                6-7  seconds (estimate)
Fuel Economy         EPA 52/45 mpg city/highway