June 23, 2006
Click image to enlarge. Photos: Bill Petro, Chris Nefs, Paul Strak, Lexus, a division of Toyota Canada Inc.
By Greg Wilson
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“Performance hybrid” might seem like a contradiction in terms, but the performance numbers for the new 2007 Lexus GS 450h Hybrid sedan speak for themselves: 0 to 60 mph (97 km/h) in 5.2 seconds, 30 to 50 mph (48 to 81 km/h) in 2.7 seconds, average fuel consumption of 8.3 L/100 km, and exhaust emissions that meet stringent Super Ultra Low Emissions Vehicle (SULEV) standards. Propelled by a combination of a 3.5-litre V6 engine, electric motor and powerful battery, the new GS 450h is not only faster than its competitor’s V8-powered luxury sedans, it’s also much more fuel efficient and kinder to the environment – at least as far as exhaust emissions go.
Stuart Payne, Director of Lexus Canada at the media introduction for the 2007 Lexus GS 450h, explained it this way: “To date, when people think of hybrid technology, they tend to think ‘fuel efficiency’. While this is an important benefit, I believe the real advantages are the performance gains and the reduced emissions that hybrid technology makes possible.”
So there you have it: the GS 450h is a “have-your-cake-and-eat-it-too” performance sedan that makes no sacrifices in performance for significant fuel economy gains and emissions improvements.
What’s really interesting, to me at least, is that the GS 450h weighs over three hundred pounds more than some of its V8-powered competitors! And yet, it’s quicker in a straight line. With hybrid performance vehicles, ‘big and heavy’ doesn’t necessarily mean ‘slow and cumbersome’. In fact, the combination of gasoline and electric power is redefining the traditional relationship between engine size, vehicle weight, performance and fuel economy that we thought we all knew!
GS 450h vs GS 430
First, let’s take a look at the differences between the GS 450h and the GS 430. The two cars look almost identical, but subtle exterior differences include a “GS 450h” emblem at the rear,
a “Hybrid” emblem on the side rocker moulding, and special 18-inch alloy wheels.
Inside, the GS 450h’s instrument panel includes a centre display with an “Energy Monitor” showing real-time energy consumption and average fuel consumption, and to the left of the speedometer is a “Power Meter” with a Kilowatt reading that replaces the tachometer.
Another key difference between the GS 450h and GS 430 is the amount of trunk space. Because of the large battery positioned behind the rear seat, the GS 450h’s trunk is only 280 litres (9.9 cu. ft.) vs the GS 430′s trunk with 430 litres (15.2 cu. ft.). That’s a 35% reduction in trunk space! And with the extra battery and hybrid hardware to carry around, the GS 450h weighs 175 kg (386 lbs) more than the GS 430. Yet, as I mentioned, the GS 450h is quicker in a straight line.
Lastly, the GS 450h is priced slightly higher than the GS 430: $76,900 vs $74,700.
GS 450h hybrid powertrain
The GS 450h’s sophisticated hybrid powertrain is state of the art. It’s a full hybrid, meaning that it can operate on the gasoline engine alone, the electric motor/battery alone, or a combination of the two, depending on power requirements. The gasoline engine is a 3.5-litre V6, first seen in the Lexus IS 350, and in the GS 450h it makes 292 hp @ 6,400 rpm and 267 lb-ft of torque @ 4,800 rpm. That compares to the GS 430′s 4.3-litre V8 with 300 hp @ 5600 rpm and 325 lb-ft of torque @ 3400 rpm. However, the GS 450h has more torque overall due to its powerful electric motor – more about that in a minute.
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The 3.5-litre V6 has dual overhead camshafts, four valves per cylinder, Dual Variable Valve Timing-intelligent (VVT-i) on the intake and exhaust cams, and both direct and port fuel injection systems that inject fuel directly into the cylinders as well as into the intake ports. Lexus says this increases the compression ratio (11.8:1) to enhance performance under high load, while increasing fuel efficiency under low and moderate loads. This fuel injection system received the “Best New Technology” award for 2006 from the Automobile Journalists Association of Canada.
An electric motor provides 197 hp (147 kW) @ 5,615-13,000 rpm, and a torque rating of 203 lb-ft (275 kW) @ 0-3,840 rpm, all of which goes to the rear wheels. Note that the generous torque of the electric motor is available as soon as you put your foot on the accelerator, giving the GS 450h its formidable acceleration. Another electric motor powers the electrical systems and recharges the battery. Both are housed inside the CVT (continuously variable transmission) which, by the way, is the world’s first longitudinal CVT in a hybrid vehicle. Though it’s an automatic transmission with no shift points, the CVT features a sequential manual-mode shifter with six ‘gears’ for those who want to shift manually.
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The hybrid drive system also includes a 288-volt nickel metal hydride battery, and a compact Power Control Unit (PCU) that converts the battery’s DC power to AC power. The hybrid drive system (engine/electric motor/battery/PCU) produces the equivalent of 339 horsepower, which Lexus says offers the performance equivalent of a 4.5-litre V8.
As I mentioned, the GS 450h offers significantly better fuel consumption than its V8 competitors, as well as fewer NOx, hydrocarbon, and CO emissions, and less carbon dioxide (greenhouse gas) emissions. Official fuel consumption figures are 8.7 L/100 km (32 mpg Imp.) in the city and 7.8 L/100 km (36 mpg Imp.) on the highway. Compare that to the GS 430 with 12.7 city/8.5 hwy and the GS 300 with 10.7 city/7.2 hwy. In fact, the GS 450h’s combined fuel consumption rating of 8.3 L/100 km (34 mpg Imp.) compares to an average of 13.8 L/100 km (21 mpg Imp.) for its performance-equivalent V8 competitors (BMW 550i, Audi A6 4.2, Mercedes-Benz E500, Infiniti M45). Compared to those vehicles, Lexus says the GS 450h will save 414 litres of fuel per year and require ten less fill-ups, based on 20,000 km driven annually.
At 240,000 kilometres, Lexus estimates that the GS 450h will have saved 14 metric tonnes of carbon dioxide from being released into the atmosphere.
All of this sounds almost too good to be true. Is it? Our brief road test revealed some trade-offs.
The GS 450h is the first full hybrid with a front-mounted engine and rear-wheel drive. Front engine/rear-drive is the layout preferred by luxury automakers in the mid-size segment because it provides better ride and handling characteristics. So Lexus really had no choice but to adapt the hybrid drive system to this layout, something we’ll also see on the upcoming full-size LS 460 Hybrid.
With a fully independent suspension (front double-wishbone/rear multi-link), front and rear stabilizer bars, an Adaptive Variable Suspension (AVS) system that constantly adjusts shock absorber settings in response to road surfaces and vehicle speed, and standard 245/40R18-inch performance summer radials, the GS 450h really carves up the road and sticks to the pavement like glue. Yet, in typical Lexus fashion, the driver feels almost removed from what’s going on because the car is so quiet and easy to drive.
With so much power on tap right from the get-go, there’s no sensation of it being overweight, and with its computer-controlled adaptive suspension, it rides comfortably and offers balanced handling. Throw it around a bit though, and its mass becomes more apparent, confirming that Newtonian physics laws still apply.
The gasoline engine/electric motor combination provides plenty of instant torque, and with a stab on the accelerator, the GS 450h just leaps off the line and rockets away. Any wheelspin is countered by standard traction and stability control. Under hard acceleration, the CVT transmission will wind the engine up quickly to redline and stay there until you back off, but there’s so much torque that you don’t need a heavy right foot to move quickly.
The hybrid drive system automatically turns off the gas engine at stoplights to save fuel, but not all the time. It depends on the current operating conditions. When accelerating at low speeds, the electric motor operates by itself and saves fuel, but if more power is required the gas engine turns on automatically. Under electric power only, a slight whine can be heard from the electric motor, and even when the gas engine turns on, the car is very quiet.
Under braking, the driver will notice some additional braking force being applied by the regenerative braking system (which uses braking energy to help recharge the battery) but there’s no lack of stopping power. Four big ventilated disc brakes assisted by ABS, Electronic Brake force Distribution (EBD), Brake Assist (for extra brake force in panic situations) have no problem hauling down this heavy cruiser.
The GS 450h features Lexus’ Vehicle Dynamics Integrated Management (VDIM) system which automatically makes subtle adjustments to steering, acceleration, and braking based on driver input and road conditions to help maintain control and stability. VDIM includes traction control and stability control – the latter automatically cuts the throttle back and brakes individual wheels to help prevent understeer or oversteer in a slippery curve. I was able to test this system on a test track in a GS 430 last year, and it worked well without being intrusive or bothersome.
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The GS 450h’s electric power steering with variable assist provides quick response and low effort at city speeds while a firmer feel at highway speeds. Its turning diameter of 11.2 metres (36.8 ft.) is tight enough for easy u-turns.
The GS 450h is like the GS 430 in many respects, but drivers will notice more low-end torque, and a difference in the way the CVT transmission performs under acceleration.
The GS 450h is a loaded luxury car, and there are no options. Its high quality leather and woodgrain interior features a standard DVD navigation system with a screen that can be used for the map, hybrid drive display, or back-up camera when in Reverse gear; an automatic climate control system, and a Mark Levinson Audio system with cassette/CD/DVD changer, MP3/WMA capability, Bluetooth capability, and 14 speakers.
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Other standard features include power tilt-telescoping wood steering wheel, heated front seats, ‘smart’ key entry system with push-button starting, power rear sunshade, power windows with automatic up and down function for all windows, power moonroof, factory-installed first aid and tool kits.
There are eight airbags: dual-stage front airbags, knee airbags for both driver and front passenger, front and rear seat side airbags, and curtain airbags for both rows of passengers. Five adjustable head restraints, and five three-point seat belts with pre-tensioners and force limiters are provided.
Though it’s a mid-sized sedan, the GS 450h’s interior feels a bit cosy, particularly for rear passengers. The centre rear position in particular has a raised cushion and uncomfortable backrest. Just as the exterior styling seems to be wrapped tightly around a form, the interior seems to wrap around the driver and occupants. It’s partly because of the high window sills, thick pillars and low rear roofline. Whether you like this cosy feeling will be a matter of personal preference, but I would recommend that taller drivers check to see there’s enough headroom and legroom – front and rear.
The instruments and controls are easy to see – though the unique ‘stainless steel’ gauges are easier to read with the lights turned on. The centre display includes big buttons for easy operation of the navigation, audio and climate control system, with the major heater controls below the screen for easy use. A display for the hybrid system gives real time information as to energy being used and fuel consumption, but of course you can’t see this and the navigation screen at the same time – or the audio or heater screen functions.
If you plan on going on a trip with a full load of passengers, the GS 450h’s 9.9 cubic feet trunk may be too small. Competitor’s vehicles offer between 15 and 18 cubic feet. And of course, the GS 450h has no folding seatbacks.
With class-leading acceleration, fuel economy, and emissions performance, the new Lexus GS 450h performance hybrid sedan sets new standards in the mid-size luxury performance class. But there are some compromises such as less trunk space and a heavier curb weight, and some people might find the interior a bit cosy.
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