2004 Toyota Prius

Hey there, time traveller!
This article was published 29/08/2003 (8257 days ago), so information in it may no longer be current.

PASADENA, Calif. — I have driven the future.

Sitting in the 2004 Toyota Prius, key in pocket, is all that’s needed to prepare the car to move. Press the brake and, like turning on a DVD player, push the power button. Nothing, aside from the instrument panel lighting up and displaying the word “ready”, happens.

A slight left-and-upwards tap of a short joystick and press of the accelerator and the Prius accelerates rearward. Silently.

Tapping the same joystick left and down readies the car for forward motion. Still, nothing, aside from the transmission indicator reading ‘D’ for Drive, happens.

It’s only when you push the accelerator does anything happen. Generally at this point, the gas engine starts, but not always.

Where’s George Jetson when you need him?

When it’s time to park, hold the brake and press ‘P’ for Park; the transmission disengages and the parking pawl clicks in to keep the car still. Then turn the power off. Or, simply turn the power off and it all happens automatically.

It is hard not to think that as technology evolves and more conventions are discarded, this is what driving will become.

And that’s not even counting the gas savings from the Prius’ hybrid gas-electric powertrain.

The 2004 Prius is what environmental-automotive engineers dub a full hybrid, able to run entirely on gas or on electric as well as on a combination of both. Other hybrids on or coming soon to the market are considered soft hybrids, needing at all times the gas engine for propulsion, with the electric kicking in only when needed.

At the gas-engine heart of the Prius is a 1.5-litre, four-cylinder Atkinson-cycle engine. It delivers its power to a power-splitter that splits power between an electric generator and the drive wheels.

At its electric-motor heart is a 50 kW bi-directional electric motor that feeds a planetary gearset in the Prius’ transmission.

The Atkinson-cycle gas engine, with its long expansion stroke, is known for exceptional effficiency but is no powerhouse. It produces but a measly 76 horsepower and puny 82 pound-feet of torque. By itself, it would mean a car that does 0-100 measured in minutes, not seconds. But the electric motor adds 67 horsepower and 295 pound-feet of peak torque (more torque than a Porsche Boxster, by the way) from 0-1,200 rpm.

Yes, from 0-1,200 rpm. That torque is there right now.

Unlike conventional automatic transmissions that run through a series of gears to accomplish gear changes, or belt-driven continuously variable transmissions that vary the radii at each end of the belt to manage torque, the Prius planetary gearset works in strange, almost alchemic, ways.

The easiest way to think of it may be as a four-way power coupler, taking power from the electric motor and gas motor and delivering power to the generator and drive wheels. By varying the speeds of the electric motor and the generator in relation to engine and vehicle speed, the planetary gearset is able to provide the action of a continuously variable transmission.

Strangely, what the planetary-gear transmission means is that the gas engine cannot be used for reverse, since there’s no provision for direction change. “You can’t make a gas engine go backwards,” says Dave Hermance, one of the lead Prius engineers. Because the planetary gears do not provide for direction reversal, the answer is to simply run the electric motor backwards for reverse and freewheel the gas engine.

Hence, the silent rearward motion. It’s so quiet, Toyota programmed in a reverse beeper to sound inside the cab to let drivers know the car is in reverse. It’s so quiet, Toyota should have placed a reverse beeper outside the car as well.

Making seamless the transition from regular cars to the Prius was a priority for chief engineer Masao Inoue. A priority almost to the point of obsession. Ever take your foot off the brake at a stoplight? What happens? The car, thanks to the residual torque available at idle, creeps forward, doesn’t it?

That wouldn’t normally happen with the Prius, since the gas engine shuts down instead of idling. Not willing to let even that concession to regular cars slip by, Inoue’s team programmed the electric motor to provide the “stoplight creep” of conventional cars when the brake pedal is released.

In some hybrid cars, the Honda Insight for one, the air conditioner runs, like almost all cars, on a compressor driven by a fan belt on the gas engine. OK, but what that means is if you want air conditioning, you give up the engine-stop-at-idle feature. Or, if you want engine-stop-at-idle, you give up air conditioning. Try that on days such as during last week’s heat wave.

On the Prius, the compressor runs much like your compressor at home: driven by an electric motor and not by the fan belt. That requires an inverter to convert the direct current from the Prius’ large-capacity battery into three-phase alternating current to drive the motor, but it means the air conditioning is not dependent on the gas engine.

Converting the battery’s DC to AC was necessary for the electric motor in the powertrain anyway, so why not power the air conditioning too?

And yet some conventions were abandoned entirely, such as the typical PRND21 layout of a transmission shift lever. And who ever imagined a POWER switch?

Two major advances contributed to the new Prius. The first was the development of a high-density nickel metal-hydride battery that allowed Toyota to get the same amount of power as in the out-going Prius in a much smaller package.

That let them put the battery on the floor of the cargo area, allowing for more cargo room, fold-flat rear seats and an under-floor storage area for the spare tire and more. The previous Prius batteries were mounted to the rear seat seatback, cutting into trunk space and ruling out folding seats.

The other was the development of the high-voltage circuit that is able to increase the voltage from the battery’s 200 volts to 500 volts, allowing for greater power from the electric motor for a given amount of battery power.

Both let them significantly increase the Prius’s size, inside more than out. The length grows by 140 millimeters to 4,445 mm, with width by 30 mm while the height stays the same.

But the real story is inside, where there is an additional 61 mm of interior width leading to an additional 11 cubic feet of interior volume. Though the exterior dimensions don’t suggest it, the growth in interior volume moves the Prius from the compact category in 2003 to mid-size in 2004.

I’ll admit I was originally none too fond of the 2004 Prius styling. Well, that was then, this is now. It has grown on me to the point I rather quite appreciate it.

It’s certainly the most avant-garde design to ever come from traditionally, painfully conservative Toyota. The rear may remind of the Pontiac Le Mans hatchback from the 1980s, but here the liftback concept is much more elegantly executed. The slight forward tilt of the vertical rear plays well off the tapered roofline.

Inside, designers have rethought much of what is traditional automotive design. The instrument panel is not, like the previous, centre-mounted, but it is so low-profile it provides the same benefits without the drawbacks. It provides the relevant information: speed, gear selection, turn signals and maintenance indications like temperature and oil. It is offset slightly, but its low profile means it is almost directly below the windscreen, barely any movement from the line-of-sight is needed.

To the right of the steering wheel, from the top, is the power switch, below which is the slot for the key fob. To the right of that is the transmission joystick control, above which is the Park button. Since many automatic transmissions now feature no mechanical linkage between shifter and transmission, the PRND321 (or PRNDL) convention is sure to be history in the not too distant future.

The B position (see picture) operates a bit like a forced downshift, except in the Prius, it invokes a more aggressive form of regenerative braking, which is what charges the battery. It also results in a nice bit of powertrain braking (not engine braking, since the effect is largely from the generator).

So, how is it to drive? It is a lot like a regular car, but not entirely.

There is, thanks to the almost-instant torque delivered by electric motors, plenty of starting power and lots of hill-climbing ability.

The continuously-variable transmission action of the planetary gearset means there are no shifts to feel and the torque management system means the car does indeed accelerate faster than normal cars, but it doesn’t feel like it since torque management removes that initial kick that’s felt in other cars.

Needing to put your foot on the brake to turn it on and hearing the gas engine cut out when it’s not needed are also unusual.

Yet by and large, it is a normal car. It gives up nothing in acceleration to its eco-friendliness, it is fuelled like any other, the air conditioning runs for as long as you need it and there’s plenty of space for people and cargo.

The Prius’ pulling power was evident on our mile-high climb up Mount Wilson, where the majority of accompanying photographs were taken. It handled as well as or even better than most other cars in its category thanks to the low position of the electric motor and its subsequent lowering of the car’s centre of gravity.

The position of the batteries, rearward of the rear seat, means a front-rear weight balance similar to many rear-wheel drive cars.

One question that invariably arises in any discussion about hybrid gas-electrics is maintenance.

Of course, it should be pointed out that the Prius handles all charging itself. There is no need to plug in the batteries for charging as with a straight electric car.

But what about that battery? It is not a cheap item, to be sure. But the Prius qualifies for PZEV emissions rating, which not only counts the stuff coming out of the tailpipe, but in some instances, what’s coming out of the owner’s wallet, as well.

So for PZEV status, (Partial Zero Emissions Vehicle — yeah, I know, you can’t divide zero but that’s bureaucracy for you) all powertrain components, and in this case, that includes the battery, must be warranted for 240,000 kilometres. And Hermance says Toyota’s testing suggests that beyond that, the rest of the vehicle will wear out before the battery does.

“We’re confident the battery is good for the life of the vehicle,” he said.

We’ll see, but 240,000 kilometres is probably as good as any warranty is going to get.

So how much is this going to cost? As much as last year’s, but not more. The starting price for the 2004 Prius is $29,990, the same as the 2003 Prius but in a larger, more well-equipped vehicle.

The up-market Prius adds vehicle stability control, six-speaker JBL audio system, front-seat-mounted side- and side-curtain airbags, anti-theft system, ‘smart key’ system, fog lamps and garage door opener, and starts at $34,055.

Both prices are within spitting distance of the average for mid-size sedans.

Is the Prius the last word in the future of automobiles? Hardly. It may sip gas at a rate that would give teetotallers envy, but it still uses gasoline.

Like Rome, the future won’t be built in a day. But engineers at Toyota, Ford, Nissan, Honda, GM, Chrysler and most other major carmakers are learning more about fuel-saving technology every day. Developments such as the Prius’ planetary gear transmission, high-voltage conversion circuitry and high-density battery all offer important clues for future research.

What carmakers learn from building stepping stones such as the Prius and upcoming Lexus RX400H hybrid will, barring a complete revision of the laws of physics, help future researchers when it’s time to finally make the break from petroleum.

Will that break be to hydrogen? Probably.

What makes that break hard to acheive is the relative simplicity of gas engines and the almost unmatched energy density of gasoline. Because hydrogen is so light, even the best hydrogen vehicles today — including fuel cell vehicles — need fuel tanks almost twice the size of a gas tank to go half the distance.

I would wager that the first viable hydrogen-powered car will be a hybrid. Like the Prius, it would use recovered energy from braking stored as electricity to augment power from either a hydrogen fuel cell or an internal combustion hydrogen engine. That would allow a vehicle to cope with the reduced range of hydrogen and still achieve usable range.

For that, several things must happen, not the least of which is wider availability of hydrogen: packaging of hydrogen fuel tanks must improve to leave some usable cargo room in the vehicle; battery technology will have to become even more refined than in the 2004 Prius; fuel cells will have to shrink in size to co-exist with batteries and means to produce and distribute hydrogen cheaply and energy efficiently must be found.

Also, when hydrogen burns in the presence of normal atmosphere, nitrous-oxides (more greenhouse gases) are formed at rates that rival gasoline. Emissions technology will have to deal with that. (In a fuel cell, hydrogen’s promise of delivering only water as waste is realized.)

All of which means that while the Prius may not be the entire future, it’s a good beginning.

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