Lexus GS 2006 Review

Local Launch       

Not so much
Loss of boot space
Fidgety low speed ride
Lack of headroom

The GS450h does not have a 4.5-litre V8 as its model number would indicate. Instead, 450 denotes the fact that its combined power sources deliver “22 per cent more power than the most powerful model in the Lexus range” according to Lexus. For most of the time, the powertrain replicates the sensation and linear delivery of a very fast and smooth electric loco. Buyers of the GS450h do not have to come to grips with oddball looks and packaging, loss of performance and equipment or face a new way of driving to experience hybrid motoring.

In other words, it is technology that can be installed into an existing large car tomorrow and turn it into 1.8-2.0-litre economy cars in terms of fuel consumption without loss of performance. The main penalty is the 69kg metal hydride battery pack (similar to a mobile phone on a larger scale) that also eats into boot space over the rear axle.

Even if is smaller than an LPG tank, serious golfers and their partners need not apply. In the Lexus GS450h, the smaller size and the weight-saving technology of the V6 petrol engine have cut its weight back to an installed 177kg compensating for some of the battery pack. The all-up weight of 1865-1930kg is comparable to top shelf V8 luxury models. The car also boasts almost perfect 50:50 weight distribution -- important (in this case) for the regenerative braking that acts through the back wheels.

It is worth noting that Holden’s latest 6-litre V8 with its simpler and lighter pushrod technology weighs 180kg and delivers a superior power output to the GS450h’s combined 254kW. It’s the combined torque output of the GS450h powerplants and how it is used that delivers V8 performance with four-cylinder economy.

By exploiting the instant 275Nm torque of the main electric motor to move the car off the line then feeding the petrol engine’s output through the continuously variable transmission, Lexus has made the switch between power sources imperceptible while eliminating wasteful torque-converters and clutches. Depending on the charge in the battery pack, the petrol engine supplements the electric motor only when required.

The GS450h has its own self-contained energy loop and like its Prius stablemate does not require electricity from an external mains source, only petrol. During a hard run around the Bathurst circuit, the charge of the battery pack would be heavily depleted after the electric motor’s full performance was required to supplement the petrol engine for a flat out uphill run. On the way down, the regenerative braking ensured it had enough charge to do it all again.

Lexus makes several bold claims for what is the world’s first volume production rear-drive hybrid. By pricing it at $121,990 or just $9690 above the GS300 Sports Luxury model and $15,210 below the GS430 V8 model (to read CarPoint's review click here), it is a viable alternative in this market niche. If leasing deals award it higher residuals than normal, the difference in monthly payments between the GS300 could well be negligible. Data from existing Prius deals would enable financiers to make such a call.

Although Lexus claims the battery pack will last the life of the car, it is expensive and its life will be shortened by irregular usage so exactly how the used market responds to such a variable at the close of a five-year lease remains to be seen.

Depreciation at the top end of the market in raw dollar terms can be savage compared to any petrol savings so extra gains or losses here could make a huge difference to the bottom line.

Routine maintenance according to Lexus should be the same as for the GS300.

The GS450h with its 7.9lt/100km combined fuel figure betters the GS430 by 31 per cent and the GS300 by 19.3 per cent deliverying a potential range of 822km. Actual savings will vary according to usage and may not add up for some drivers hence the emotive Lexus push over the “guilt-free” high performance.

Owners who must use their cars everyday with the right combination of inner city and freeway/open road cruising to keep the battery pack charged should get the best out of the hybrid powertrain. The GS450h’s real agenda could be to position the hybrid powertrain away from the abstemious Toyota Prius and Honda Insight as something sexy and prestigious in preparation for mass fitment in the Toyota range, an outcome hinted at during the launch.

FEATURES
Because the GS450h prime focus is a top-shelf luxury alternative, not a green machine --virtually nothing is missing. The tachometer is replaced by a power meter which provides an instantaneous reading of the number of kilowatts required for what you are doing. A neat dash EMV graphic indicates whether you are drawing on the electric or petrol motors, or both, or if you are putting charge back into the system.

The EMV screen will track energy usage in bar graph form over a given trip as well as display a more detailed graphic of what’s happening inside the energy loop. The same screen also covers the rear view camera function. Standard DVD satellite navigation can plot a route across Australia.

There is Bluetooth hands-free mobile phone connectivity, MP3/WMA compatibility and DVD movie capability in the entertainment system. The 14-speaker Mark Levinson premium sound system features a six-disc CD/DVD changer.

A smart security system allows a push button start as soon as the key is detected inside the vehicle. The key can live in the centre console once inside when it doesn’t have to physically contact any part of the car. The dual-zone climate control for the cabin is supplemented by climate control for both front seats.

Rain-sensing wipers, electro-chromatic exterior mirrors, rear power sunshade, glass sunroof, multiple memories for seating positions on both sides and a concealed control panel for cabin switch gear are all part of a technology-loaded cabin that is pleasingly simple and easy to operate.

Over smooth surfaces, the ride and solid feel of the body are exemplary but the 18-inch alloys with 40-series low profile tyres can make the suspension feel and sound quite busy on choppy secondary roads at low speeds. It is not bad but prevents the Lexus from taking top-shelf comfort honours when several local cars at a third of the price do better.

The L-Finesse body design introduced in February 2005 may have the pleasing profile of a sporty four-door coupe but the radical hoop-like roofline generates thicker windscreen pillars than desirable and cuts in too close to the driver’s head. This cuts into rear cabin space too and may be an ongoing problem with taller front seat occupants as the radical roofline also requires occupants of the rear seat to sit low and stretch out when headroom is also tight. Families need to try the GS450h with all occupants onboard before committing.

In terms of finish and materials, the Lexus is up there with the best. The range of front seat and steering column adjustments caters for most drivers. The heating and ventilation system allows you to easily bypass the climate control system and select a simple fresh air function that delivers copious amounts of sweet Aussie country air; an unnecessarily complex task in too many luxury cars.

SAFETY
A detailed examination of GS450h safety features would fill most reviews. Primary safety features include an adaptive front-lighting system, front and rear fog lamps, rear view camera for reversing, radar active cruise control and a Pre-Collision system which can increase braking force if sensors determine that a crash is imminent. It has audible distance warning systems for both the front and rear.

The ventilated front disc brakes are a generous 334 x 30mm with ventilated rear discs. The class-baseline of ABS, EBD (Electronic Brake Distribution), Lexus brake assist, traction control and vehicle stability control (VSC) are all there. It also shares the GS430’s Adaptive Variable Suspension, Variable Gear Ratio steering and the Lexus Vehicle Dynamics Integrated Management (VDiM) which brings active steering into the VSC system.

To supplement the conventional braking system, the GS450h exploits the hybrid powertrain for regenerative braking. The vital PCU/inverter nerve centre which controls the flow of energy and choice of motive power also directs braking effort from the brake pedal to the regenerative braking system. At low speeds and in stop-start traffic, it can provide most of the braking.

If it all goes pear-shaped, the GS450h has no less than 10 airbags including front knee airbags and side airbags for rear seat occupants. 

MECHANICAL
There is little point developing the ultimate hybrid powertrain system if the petrol engine upon which it depends is thirsty and inefficient.

The special 2GR-FSE high compression ratio (11.8:1) version of the Lexus quad-cam 3.5-litre V6 has roller rockers, high tumble inlet ports, swirl-control valves in the inlet ports, electronic Acoustic Control Induction System (ACIS) and all aluminium block and heads. The dual wall stainless steel exhaust manifolds and inbuilt three-way catalyst cut emissions and boost cat temperatures from a cold start, essential when the petrol engine is rested during different phases of the energy loop. A timing chain, direct ignition and special high silicon low friction pistons ensure low maintenance efficiency over a long life.

This petrol engine is also the first of its type in Australia with two fuel-injection systems: direct high-pressure injection to provide a cooling effect for reduced detonation and low fuel consumption in high load situations and low-pressure multi-port injection for optimum economy in light load situations. Its 218kW and 368Nm are not only used for motive power but to power its own starter motor in generator mode when required to top up the battery pack.

The L110 transmission/electric motor module built by Aisin contains the two water-cooled motor generators, one called MG1 to start the petrol engine then act as a generator and the other, MG2, to provide motive power or act as a generator under braking. This system has its own cooling system separate from the petrol engine with its own radiator, water pump and water filter. Several planetary gear sets inside the transmission transmit the various combinations of petrol and electric power with a two stage reduction gear for high and low speeds.

The driver controls it by a conventional centre auto selector lever. By programming the “wet brakes” and the engagement of the two-stage reduction gear inside the transmission, it also offers a manual sequential function that replicates the different ratios in a conventional automatic transmission. Because there is no reverse gear, selecting R engages the MG2 electric motor with reversed polarity.

The key is the amazing PCU (Power Control Unit) and inverter which automatically controls the functions of the powerplants, generators, braking and transmission based on driver commands though conventional controls. Its achievement is managing all these systems while never providing even the slightest impression to the driver or passengers that the GS450h doesn’t contain anything other than the simplest single linear power source.

The challenge of housing the PCU/inverter was met by halving its size and mounting it under the bonnet after moving the engine’s battery to the rear. It is water-cooled by the supplementary cooling system.

COMPETITORS
Lexus muddies the issue of rivals when the GS450h is presented primarily as a high-performance sedan with the benefit of 2.0-litre four cylinder economy. Even if there are several elite prestige V8 models that can match its strong performance, none come close to the claimed 7.9lt/100km fuel economy.

If you are attracted to what the GS450h offers, the Jaguar S-type Diesel should be of interest. It offers a more practical cabin, larger boot, fold down back seat, smoother ride, similar performance in practical terms, an overall 7.8lt/100km fuel figure and a more involving driving experience. It’s not quite as slick in several areas as the Lexus but at only $101,490, it has a lot going for it.

The Mercedes-Benz E280 CDI diesel starting at $96,500 has most green credentials covered with a 7.5lt/100km overall figure. Its smooth seven-speed automatic and high 440Nm torque output deliver frugal performance for what has to be one of the most rock solid if slightly austere buys in today’s market. An imminent mid-life makeover should make it even more attractive.

BMW’s latest 530d diesel is the most formidable alternative as it also delivers 7.5lt/100km fuel economy and starts at $114,500. Its 160kW/480Nm engine delivers V8 performance faster than the Jaguar and Mercedes-Benz in what many perceive as the class-leading package for prestige, style, driver pleasure and competence.

With overseas tests suggesting the Lexus should fry the zero-100km/h sprint in the 5sec range compared to the low sevens for the best of the diesels, the Lexus GS450h may really prove to be in a performance/economy class of its own.

ON THE ROAD
The GS450h’s most advanced and intriguing achievements may be its least endearing. There is no denying its outstanding performance and willingness to withstand serious punishment as Lexus demonstrated over and over in several sprints up the Mount Panorama circuit at Bathurst.

Driving off from rest is seriously weird. Once behind the wheel, you don’t even have to insert a key. You press the Power button in Park then select Drive, kick the parking brake and away you go without a sound.

There is no starter, nothing. Bystanders are at risk when there is absolutely no warning that what looked and sounded like a stationary car is now moving. In fact, the absence of wind and mechanical noise could well catch out pedestrians and cyclists even on the highway.

It is only when you want a boost in acceleration that there is a slight increase in noise levels as the petrol engine stirs into life and joins seamlessly into the driving equation. Even then it’s hard to pick when its sound or note is not always related to any change in speed.

Under fierce acceleration there is a sense of it working but it doesn’t rise and fall as you progress. It seems to hang onto a constant note as the electric motor and transmission do their business. The sequential shift function does little under power but can artificially generate an engine braking effect depending on which ‘gear’ you select.

The overwhelming sense is how ridiculously slow the whole car seems when the noise levels at 100km/h are probably the same as most cars at 15-20km/h! This is one car that must be driven with eyes glued to the speedo. It leaves you with a sense of amazement, not involvement. Just how this would leave you feeling over an extended ownership period is an unknown.

The suspension at Australian cruising speeds seems to register every bump and irregularity before it knocks off the rough edges. This suggests the car is set up for much higher speeds. Indeed, there are indications that it would smooth out beautifully.

The steering with all its wizardry is quite numb at low speeds but also livens up when you start making the chassis work. During the high-speed Bathurst trials, the GS450h was a joy to place in the corners when the neutral handling and smooth power delivery allow the driver to follow a very accurate line.

The energy reporting systems certainly leave you pondering over exactly how much grunt you really need. Even going up a hill at 100km/h, the system rarely had to deliver much more than 50kW while just 25kW keeps you moving at 100km/h on the flat.

If the GS450h is all we are left with as petrol draws out of reach, there are worse fates.