The Toyota Prius Hybrid - Part 1

Take a long look at one of the most exciting, intelligent vehicles you'll see on Australian roads.

The Toyota Prius is the first hybrid-powered 4-door sedan available on the Australian market. It's a car that offers all the practicality of an everyday small-medium sedan, but - thanks to its electric power hybrid technology - produces a claimed 80 percent less emissions and uses up to 50 percent less fuel than an equivalent vehicle. It's a phenomenal piece of engineering.

So - first - what is the Toyota hybrid system and how does it work?

The Prius is propelled by two parallel power sources - a petrol engine and an electric motor with a battery pack. The petrol engine is used only under acceleration or for medium-to-high load conditions. For the remainder of the time - when there's only a small amount of power required - an electric motor is used to drive the wheels. At maximum throttle, however, the Prius effectively compounds both drive sources for the maximum available power.

The key philosophy behind the hybrid system is to use electric power in instances when the petrol engine runs relatively inefficiently.

The petrol engine itself is a VVT-i, DOHC, 16-valve 1.5-litre four cylinder featuring electronic throttle control, direct fire ignition and a MAP sensor. Interestingly, the engine employs the Atkinson cycle principle which - by keeping the exhaust valves closed until the end of the expansion stroke - is said to offer greater efficiency than a conventional Otto cycle engine.

Peak power is achieved at relatively low revs - 53kW at 4500 rpm - while torque is listed at 115Nm at 4200 rpm.

Working alongside the petrol engine is the electric drive motor - this produces 33kW all the way from 1040 to 5600 rpm. As mentioned, at maximum throttle, the Prius combines the petrol engine's 53kW and the electric motor's 33kW to achieve an 86kW total output.

The electric motor's associated battery pack - which is located in the boot - comprises thirty-eight Nickel-Metal Hydride (Ni-MH) cells, giving a total of 273.6 volts.

Maintaining battery charge is a regenerative brake system, which converts the vehicle's kinetic energy into electrical energy. The regenerative system is engaged whenever the throttle is released or the hydraulic brakes are applied. The system is used to slow the vehicle's forward motion and - using the traction motor as a generator - produces current to top-up the battery pack.

Depending on conditions, battery charge can also be derived from the petrol engine; a percentage of the engine's output is used to generate the electricity to charge the battery cells.

Note that the Prius' battery pack does not require charging from an external power source, such as an electric socket.

The hybrid configuration gives its largest benefit during city and urban driving conditions, where the driver is frequently on/off the throttle and stopped in traffic. Every time you touch the brake pedal or release the accelerator (to coast up to a set of lights, for example) the petrol engine is automatically switched off. There's no fuel burned and - therefore - there are none of the associated tailpipe emissions.

Sitting in stopped traffic onboard a Prius, you find yourself looking at everyone else's cars, scorning the fact that their engines are running and pointlessly spewing out emissions.

Toyota claims the Prius' levels of carbon monoxide, NOx and hydrocarbons are less than 8 percent of the official maximum level. It is also said that - during city driving - the Prius produces only about 20 percent of the carbon dioxide generated by an equivalent sized conventional car.

In terms of fuel consumption, we recorded an astounding 5.15 litres per 100 kilometres during our urban/city driving. On the open road, however, the Prius relies mainly on the power of its petrol engine and - therefore - we saw a less amazing 4.9-litres per 100 kilometres under these conditions.

While these overall fuel consumption figures are very impressive, we must point out that the Peugeot 406 turbo diesel can crack into the 5-litre per 100km bracket on the open road. Also, the sole other hybrid vehicle on the market - the $8910 more expensive Honda Insight 2-seater - can better the Prius' fuel consumption, with a claimed 3.6-litres per 100 kilometres on city cycle...

The Prius' accelerative performance scrapes in as acceptable for everyday urban driving situations. Throttle response is reasonable, torque spread is adequate and there's just enough peak power to allow for safe overtaking. A standard-fitment continuously variable automatic transmission ensures the engine is always running near its optimum rpm and - as a bonus - eliminates the disruption of making a gearshift.

Noise from the petrol engine does intrude at higher load and rpm, although - when only the electric motor is in service - the Prius creeps along absolutely silently. Driving slowly through a shopping centre car park, for example, you need to beep people out of the way who don't hear you coming...

The Prius' impressive design doesn't end with its hybrid technology.

Inside, the Prius offers excellent space and features. Its high-line cabin allows ample front headroom for the over 6-foot brigade, and there's well-up-to-standard levels of legroom and width. The driving position is very comfortable, aided by an adjustable height driver's seat and adjustable angle steering column. Visibility is excellent, but - because the bonnet slopes away out of sight - it's difficult to judge how far to edge forward when parking.

The cabin is very quiet, with absolutely no rattles or buzzes from the interior trim - the only noise that catches your ear is the distant whir of the regenerative brake system when you're decelerating.

The Prius specifications list gets a long line of ticks - twin airbags, seatbelt pre-tensioners and force limiters, power windows and mirrors, analog climate control, an in-dash 6-stack CD/tuner/cassette player, map lights, remote central locking, engine immobiliser, adjustable headlight angle and a rear fog light.

There are two separate digital displays to be dazzled by.

A centre-forward LED display shows road speed, fuel level, odometer/trip meter A and B, a gear selection indicator as well as a 'Ready' sign for when the hybrid system is running. Note the absence of a tachometer and coolant temperature gauge - there's only a blue or red temperature light to indicate cold or hot coolant temperature.

Unfortunately, viewing this display is virtually impossible when it's exposed to direct sunlight - all of the LED sectors 'illuminate' to reveal you're travelling at 188 km/h...

Located within easy reach in the centre of the dashboard is the multi-function touch screen. The 5.8-inch touch screen serves as the controls for the (average sounding) 4-speaker audio system, plus it displays hybrid system operation, fuel consumption monitor, service schedule and ambient temperature. Upon start up, a caution screen also pops up to warn you about the dangers of watching the screen while driving.

Our test vehicle had been equipped with Toyota's $3800 optional DVD-based navigation system. Plug in your destination and the system gives a visual display of your route as well as voice guidance. Points of interests, nearby petrol stations, restaurants and hospitals (including their phone numbers) are also stored in the Australia-wide map information.

The system is fast to update and doesn't get perplexed when the driver makes a wrong turn, though the guidance voice does sound a little disjointed when it gives a long list of instructions.

As a whole, the touch screen arrangement works well - but the greasy fingerprints that accumulate on the screen can become an eyesore. Oh and, just like the caution message says upon start-up, there's a good chance of having an accident if you attempt to drive and operate the touch screen at the same time.

Rear passengers also enjoy the benefits of the Prius' high roofline, with enough headroom for 6-footers. Feet room is also excellent and knee room is okay. The rear seat is comfortable, but - even although there's a retractable centre belt - fitting three persons across would be a very squeezy proposition.

Other features in the rear include a flip-down twin cup holder and seat back map pockets. A cooling vent on the rear parcel shelf is also used to maintain stable battery pack temperature.

Inside the boot are the hybrid system batteries, spanning between each wheel arch and protruding only around 8-inches above the floor of the boot. Boot volume is generous and is easily accessible - you'll also find the jump-start connectors in the left side boot trim (the Prius' 'auxiliary' 12V battery lives in the boot).

All of the hardware contained in the hybrid system contributes to the Prius' kerb mass of 1250 kilograms. This mass is poised on MacPherson-type front struts with lower L-arms at the front and a trailing-arm curved torsion beam axle at the rear. Swaybars are fitted front and rear, while a rear toe control system helps maintain rear stability while cornering.

Don't get the impression the front-wheel-drive Prius is a sharp handler, though - it isn't. It lacks front-end grip when pushed and there's considerable body roll. Toyota's focus has obviously been more towards ride quality - the Prius gives a very soft, compliant ride with minimal suspension noise. The chassis is free of nasties such as tramlining, roll and bump-steer and torque steer.

Steering is through an electric motor assisted rack and pinion arrangement. There's nice steering feel and weight at all wheel positions, and - with four turns lock-to-lock - the Prius has a nifty 9.4 metre turning circle.

The only area where the Prius feels decidedly different to a conventional car is its braking feel. It does take a while to get used to the slowing effect of the regenerative brake system - you have to vary brake pedal effort to maintain a constant rate of deceleration. This aside, the ABS and EBD-controlled front and rear disc brakes perform solidly.

The exterior design - while being a bit slab-sided and unattractive - is very aero efficient.

From nose to tail, the Prius' panels provide smooth, laminar airflow over its top section and the sharp rear cut-off and spoiler help to reduce wake. You may notice the small wind deflector forward of each wheel - these are designed to improve airflow around the tyres. Toyota claims an excellent 0.29 Cd. Other bits'n'pieces include a cooling vent for the hybrid battery in the left-hand C-pillar, side flank ridges (but no protector strips), a roof-mounted aerial and a telltale Hybrid badge on the boot. The large reflector-type headlights have powerful beams.

Wheels and tyres are 14-inch alloys wearing low rolling resistance 175/65 Bridgestone B391s.

The assembly of the Prius is as good as you'll find on any other car of comparable size. Paint quality and panel fit is very good, while interior fitment and trim quality is faultless. Toyota backs the Prius with their usual 3-year/100,000-kilometre basic vehicle warranty and a 5-year/100,000-kilometre hybrid battery warranty. The hybrid battery pack is reputedly designed to last for the life of the vehicle.

So the Prius pretty much has it all - a practical and spacious body, high levels of comfort and brilliant resource-saving engineering. There is, however, one major downside - all of this leading-edge technology comes at a fairly hefty price.

At $39,990 RRP (plus ORCs and the optional navigation system), the Prius is virtually double the price of the comparable Toyota Echo automatic sedan. Ouch...

The fact that Toyota Australia realistically expects to sell relatively few Prius is a terrible shame. It's a shame for us all. If the Australian Government were genuinely serious about reducing the consumption of fossil fuels and reducing vehicle emissions, it would be offering some kind of hybrid incentive scheme for potential buyers. Hybrid vehicles attract tax credits in America, there are subsidies in the UK and Singapore offers a 20 percent registration rebate - why doesn't the Australian government come up with some kind of sweetener?

Until that time, the Toyota Prius is a wonderfully smart, efficient car that will - most unfortunately - go largely wasted in this country.

Toyota Prius Hybrid Fast Facts... Absolutely brilliant levels of fuel consumption and emissions Acceptable performance in city/urban conditions Spookily quiet at light loads Soft, comfortable ride No driving trade-offs compared to a conventional car Spacious and practical Well appointed inside - twin airbags, digital dash, touch screen, climate control, CD stacker, optional navigation Quality assembly Expensive to buy - a car in desperate need of a Government-backed buyer incentive scheme

Test vehicle supplied courtesy of Toyota Australia.