GoAuto 16/05/2006

WITH the hybrid GS sedan, Lexus is hoping to challenge the perception of what exactly constitutes a high-performance luxury touring sedan.

Based on the successful GS300 and GS430, the GS450h shares much with its conventional petrol siblings until you notice the discrete "hybrid" badges on the rear doors or look under the bonnet and see the huge orange electrical connections disappearing into the engine bay.

Like the Prius, the hybrid GS uses both an electric motor and conventional petrol power for propulsion.

The hybrid is powered by a dual-injection – more about that later – 218kW/368Nm 3.5-litre V6 engine mated to two ingeniously constructed electric motors incorporated into the six-speed CVT automatic transmission.

One aids the petrol engine while the other acts as a generator. They are called MG1, which essentially splits the petrol engine power to propel the car and create electricity.

MG2, the second motor generator, acts as the starter motor and also a generator for the regenerative braking system.

Toyota’s engineering prowess with hybrids means it has overcome the problem of making the electric motors the same size as the existing automatic so they fit neatly in the existing transmission housing.

The key to the hybrid is the level of performance, which is comparable to the V8-powered GS430, combined with the fuel efficiency of a 2.0-litre four-cylinder hatch.

We managed 7.8L/100km in some fast highway driving, not sparing the horses, as they say.

The starting system for the hybrid is similar to the rest of the GS range, with the keyless start working a treat. Just push the start button mounted high on the dashboard and away you go.

However, the only way to tell that the car is ready to go is the illumination of the dashboard lighting. At rest, the hybrid, like the Prius, is eerily silent.

Stomp on the accelerator though and it will jump like a greyhound out of the starting box.

The hybrid will to 100km/h in less than six seconds, with the powerful electric motor delivering high levels of torque during mid-acceleration, for impressively quick overtaking manoeuvres.

The combined output of both the V6 and hybrid system is 254kW with the MG2 itself developing 147kW/275Nm from standstill.

We believe them. On a series of repeated uphill acceleration tests around the Mount Panorama race circuit near Bathurst, the instant availability of torque was something more akin to a turbo-diesel, without the noise, in the way the car accelerated away from a standing start.

With the hybrid in tandem, the GS450h delivers instantaneous torque right across the rev range. Apart from fuel economy gains, the hybrid technology ensures that the GS450h has one of the industry’s lowest emissions ratings.

Accelerate at any speed in the GS450h and one thing is quickly apparent. It’s deceptively quick, particularly from 80km/h upwards.

However, those drivers who equate performance with the loud rumble of a muscular exhaust note will be disappointed.

If you think a performance car must have the aural sensation of a V8 then you’d best shop elsewhere. This Lexus is as quiet as a stalking cheetah and just as quick.

The Lexus again goes against convention because the dual exhausts of the hybrid deliver a muted V6 exhaust note. The sound is nothing special.

And that may be a disincentive for some.

In a market sector that mates luxury with performance and just the right exhaust note, the Lexus GS hybrid stands out from its competitors by blending high performance and luxury with environmental efficiency.

As we’ve said before, the GS owes much visually to the LF-S concept car launched at the Tokyo motor show two years ago and the GS450h is almost identical to its siblings.

It carries over the long, Jaguaresque-style profile with a steeply raked front and rear windscreens and almost coupe-like sweep of the rear part of the roof, which looks good but does compromise rear-seat headroom a little.

Despite this the whole execution is handsome and with a wide track, the GS looks solid and well planted on the road, even when stationary.

Visually, only trainspotters will notice the difference between the hybrid and its twin siblings.

There are discreet "hybrid" badges on the lower chrome trim on the rear doors, as well as the boot and the five-spoke 18-inch alloys are bespoke to the hybrid.

It’s this clever detailing that makes it hard to distinguish the hybrid when it’s in traffic – that is, unless you’re stationary at the traffic lights because there is no conventional engine idle, normally associated with a petrol powerplant.

The GS hybrid just sits quietly like a Prius waiting for the light to change.

Apart from the sophisticated engine technology, the hybrid shares its double wishbone front and multi-link rear adaptive suspension with the rest of the GS range and the same slightly numb, electric power-assisted steering.

The ride is well sorted, compliant and manages to tame with European precision that stomach-churning pitch that seems to be apparent in many secondary Aussie roads.

However, after fiddling with the adaptive variable suspension we ended up letting the car decide for us. The system, like others we’ve experienced, was highly capable but you’ve still got to wonder whether an adaptive system is as effective as a well-sorted conventional damping system.

Despite its luxury credentials, the GS450h did transfer some tyre roar into the otherwise serene cabin but there was virtually no wind noise. We suspect Lexus has deliberately done this to give the hybrid a more "normal" driving experience.

In some other Lexus models we’ve driven, the eerie silence of the cabin is quite something.

Inside and throughout the cabin, the Lexus has those thoughtful touches you expect of a luxury marque and the attention to detail is exceptional. You only have to look at the door apertures of the IS and GS and you’ll see what we mean.

The leather seats are heated and cooled, the instruments bright and well laid out and the minor switchgear for things like the boot release, are hidden behind a pop-down panel to the right of the steering wheel.

Standard fare runs to climate-control, satellite-navigation, automatic headlights and wipers, a reversing camera, dashboard monitor, excellent Mark Levinson CD stereo system, pre-crash safety system, a myriad of acronyms for the safety gear, including 10 airbags that all help deliver a five-star Euro NCAP crash rating.

Like the GS430, the hybrid is fitted with Toyota’s Vehicle Dynamics Integrated Management System (VDiM) – a clever bit of software that keeps the car on track by predicting the driver’s intended course and making necessary corrections by managing the throttle, steering angle, steering wheel and brakes.

It is all accomplished without the driver knowing or feeling it happening and in the dry it’s not perceptible but when pushed to its limits, the VDiM and other traction nannies is quick to haul the car back into line.

The hybrid misses the load-thru function of the rear seats because the battery pack is sitting above the rear axle and instead of a tachometer you get a kilowatt gauge.

We can’t see the sense in that really as a tachometer would be a better gauge of engine speed, at least for the V6 petrol part of the equation.

With all the focus on the hybrid system, it would be easy to overlook the sophisticated petrol engine.

The quad-cam 3.5-litre V6 boasts variable valve timing for inlet and exhaust and intelligent electronic throttle control - nothing new there - but the V6 is also the first volume production engine with two fuel-injection systems: direct injection as well as multi-port.

Lexus claims this delivers more precise fuel monitoring across a broad rev-range.

The V6 is a pussy cat around town when it comes to quietness but once on-song, in conjunction with the hybrid motor, is a pussy cat on steroids.

And that’s perhaps the biggest anomaly with the GS450h.

It looks and feels just like an everyday GS sedan. But stroke it and it transforms into a beast of beauty.