BY TIM BRITTEN | 8th Jul 2004
Especially when you consider that the Prius is no longer the only realistic hybrid petrol-electric car available. Honda is in there batting too, with an adapted version of its Civic which undercuts the Toyota on price, if not on overall efficiency or dedication to the cause.
Both cars are tentative yet entirely practical forays into future propulsion systems. In the search for more economical and cleaner cars, they adopt existing technology and refine it to often quite amazing degrees.
In the latest version of the Toyota, the Prius II, emissions and fuel consumption are reduced to about half that of a four-cylinder Camry, yet on-road performance hardly suffers. Its 45-litre fuel tank gives a cruising range virtually equivalent to that of a medium-size four-cylinder car with a 90-litre tank.
The Prius, unlike the Honda, is a purpose-built hybrid car, sharing little with any other models from the Toyota range and offering a drive experience that requires no special adaptation.
The body is specific to the Prius, and fits somewhere between small and medium-size, with equivalent front headroom and legroom to the current Toyota Camry on a wheelbase measuring 2700mm – a mere 20mm less than the Camry.
The blatantly aero body brings to mind some Citroens of the past and has an outstanding drag coefficient of 0.26, which is lower than just about anything else on the market.
Toyota’s efforts to make the Prius easy to live with, and to inspire confidence in potential buyers are impressive. Apart from the knowledge that there is some very unconventional engineering underneath, the car presents itself in a non-challenging way.
The controls are completely familiar. If you wanted to ignore the fact this was a vehicle that relied on both a conventional engine and an electric motor to get you places, you quite easily could.
All you do is slip the "key" into its slot on the right side of the dash, press a "power" button and select drive.
What happens next borders on the uncanny. If the petrol engine is warm and you are merely edging out of your driveway or manoeuvering in a parking lot, the Prius glides forward or back with almost total silence as the sealed, 201.6-volt nickel-metal hydride hybrid battery under the rear seat sends power to the electric motor located under the bonnet.
If it’s being started from cold, the petrol engine will fire up a few moments after the power button is pressed just to bring up the correct operating temperature.
But even the way this happens is unusual. Rather than the familiar cranking sound of a starter motor, the engine is brought up to speed by a second, auxiliary electric motor that also acts as a power generator to charge the hybrid battery.
Once under way, in normal on-road use, the hybrid system performs a constant juggling act, doling out power to the wheels via either petrol or electric power, or both, or shutting them down in tandem as regenerated power is fed back into the battery. This happens when the car is coasting to a stop, or rolling down a hill.
At cruising speed, around 100km/h or so, the Prius relies mainly on the petrol engine, which is something of a model of efficiency itself with an ultra-high compression ratio of 13:1, variable valve timing, multi-valve heads, twin camshafts and all-alloy construction.
The charge in the hybrid battery varies constantly, drained then replenished as the system goes though its paces.
The bottom line is an average fuel consumption figure less than five litres per 100 kilometres which, given the size of the car and its performance, is impressive enough although it is made even more so by the concomitant reductions in exhaust emissions.
In fact, because the Prius petrol engine shuts down completely at the drop of a hat when not required, nothing whatsoever comes out of the exhaust when it is sitting in traffic, idle when other cars are idling. At the same time the electric power steering and climate-control system continue to function.
The frenzied activity that allows this is a stunning reminder of how dependent modern cars have become on electronic systems management, but there’s also some clever mechanical engineering in the Prius.
Apart from its ability to segue smoothly from fossil fuel to stored electrical energy, the car’s hybrid system is helped along by a very smart drivetrain that allows the two powerplants to work together harmoniously.
This is brought about by a very clever transmission that interconnects the petrol engine, the smaller electric (starter) motor/generator and the larger electric motor that provides the drive.
Between the two electric motors there is a planetary gear set that provides a virtual constantly-variable transmission via its two ratios (plus reverse), and the electric motor itself.
It’s not a CVT in the true sense of the word, but to the driver it feels just like the belt and pulley systems used by a number of car-makers.
So the Prius experience is a combination of normal and extraordinary normal in terms of the controls and extraordinary in terms of its fuel consumption and emissions.
And, if the driver is interested in how things are actually working, it’s possible to call up a screen that shows exactly where the power is being drawn from, and where it is going, at any given moment.
There’s also a set of bar graphs that track the fuel consumption and calculate a new average figure for every five minutes of travel. These can vary wildly, but are surprising at times, such as when creeping along in peak-hour traffic when the car will run on electric energy exclusively for a while, consuming no fuel and emitting no exhaust gas.
If the driver wants to get more serious, it’s possible to select a driving mode that favours battery charging more than normally, and amplifies regenerative braking. The only problem is that on not-so-steep inclines it drags speed down to the point where power must be used to maintain momentum.
There’s also the "EV" button on the right side of the dash that tends to favour the electric motor as the main means of propulsion, but it will still switch to the petrol engine if the battery charge level falls past a certain point.
Overall, the Prius relies most of the time on the petrol engine as the battery actually discharges quite quickly. The electric motor is mainly called on in low-speed situations.
And, with the two engines working together, the car gathers up a handy amount of combined torque (although it never feels anything like the Ferrari-beating 478Nm the Toyota press kit boasts about) and is actually very responsive to the accelerator pedal. The Prius has traction control and needs it at times.
We could go on a lot more about this intriguing Toyota, but it would be wise to mention there are things going for it other than its drive system.
The packaging, as alluded to earlier, is surprisingly efficient, with a full load-through hatchback compete with split-fold rear seat, a decent 456-litre boot and a handy, hidden compartment between the boot floor and the space-saver spare tyre.
Passenger space is pretty good too, with lots of back-seat legroom as a complement to that Camry-size front-seat area. The seats are manually adjusted and cloth-trimmed even in the $45,000 i-Tech premium model.
But the base model’s price tag of $36,990 is les than the original Prius which it overshadows in every way, including size, performance and economy.
The i-Tech version includes satellite-navigation and climate-control air-conditioning, front side air bags, curtain air bags, vehicle stability control, smart-entry and start (the car is unlocked and driven without the keys being removed from the driver’s pocket), premium JBL sound system with nine speakers and Bluetooth mobile phone compatibility - which, for some reason, didn’t work in our test car.
The fit and finish of the car is naturally faultless, everything you’d expect in a premium small vehicle.
The Prius is not exactly what everyone would expect for the money though. You don’t exactly get the cache of a European badge, or even that of a Lexus badge, and you’re more likely to be labelled a greenie than anything else if you are seen in one.
To those in the know, the Prius is a source of attention, a source of the odd double take as it reverses out of parking spots in total, eerie silence.
But on the road, particularly the open road, it’s very much like a regular 2.0-litre car: pretty quiet and handy enough when a bit of accelerative power is called for thanks to the added boost of the electric motor.
If it had to rely on just the 1.5-litre petrol engine all the time, the story would be quite different.
It’s arguable that an efficient petrol engine along, perhaps, with the cut-off function when stationary in traffic, would get close to Prius fuel economy. But even if it did, it would be a slug to drive.
The only real conventional-engine economy challenger to the Prius is the lightweight turbo-diesel, the sort of thing found with Peugeot badges, where the miserly rate of fuel sipping is similar.
In fact, one is inclined to ask how hybrid technology would work with a small turbo-diesel, rather than an efficient petrol engine, factored into the equation.
Then of course there’s the question of how wise an investment a Prius would be. Indications are that the original Prius dropped in value a little more sharply over 12 months than a comparably priced Camry, but nothing drastic.
Over a longer term it’s too early to tell, although it’s certain there will be more customers looking for a second-hand Prius than Honda managed to find with its two-seat Insight market experiment. The retained value there became frighteningly small.
And at least there is a decent warranty coverage, with the Panasonic hybrid battery covered for five years or 100,000km.
Is Prius the future of motoring? Maybe, but it’s likely to be only a part of it.