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Lexus performance hybrids driven

2008-09-30 07:38
Looks like a standard Lexus RX SUV. Under the styl

Looks like a standard Lexus RX SUV. Under the stylish exterior is an absurdly swift hybrid drive system endowing it with stunning performance and environmental impact much lower than the Witbank smokestack in the background.

Vehicle Specs
Manufacturer Lexus
Engine 3.3l, 3.5l V6,
Power 155kW @ 5 600r/min (123/50kW electric), 218kW @ 6 400r/min (147kW electric)
Torque 288Nm @ 4 400r/min (333/130Nm electric), 368Nm @ 4 800r/min (275Nm electric)
Transmission CVT
Zero To Hundred 7.3 sec, 5.9 sec
Top Speed 200km/h, 250km/h
Fuel Tank 65l, 69l
Fuel Consumption 8.1l/100km, 7.9l/100km
Weight 2000kg, 1930kg
Boot Size 439l, 280l
Airbags seven (RX400H), ten (GS460h)
Warranty 3 years/100 000km

Lance Branquinho

Since the mid 1990s car manufacturers have been teasing the public with motorshow concept hybrids from the fertile imaginations of their research and development engineers.

How these hybrid drive concepts were going to thread their way to market was unclear.

With current emissions related taxation eroding the viability of large capacity engines and escalating fossil fuel costs the time for hybrid drive vehicles has arrived.

Performance with conscience?

The GS450h sedan and RX400h SUV might not be entirely new vehicles – having been on sale in hybrid form for close on two years in other markets – but they represent a unique driving experience and product alternative dynamically.

Though local legislation does not incentivise hybrid technology vehicles yet – quite unfairly so – the Lexus hybrids offers some compelling purchasing rationale from sources not exclusively aligned with saving the polar ice caps – witness the sub six second GS450h 0-100km/h sprint time for example.

You’ll invoke the ire of Lexus engineers if you make mention of the Prius as a cousin to the GS450h and RX400h hybrids. The Lexus hybrids are petrol cars augmented by electric hybrid drive technology to render seamless, almost severe, performance at reasonable operating costs and dramatically reduced emissions.

Understandably the last point is lost on local buyers - as driving a heavily polluting car in South Africa is currently unburdened by additional taxation. Uncannily though, for something espousing Captain Planet technology, the performance imperative of the Lexus hybrid technology is an unexpected boon.

Essentially then, all traditional Lexus virtues – refinement, reliability and cosseting luxury – are given a significant performance boost from the addition of electric drive technology.

Why petrol electric and not diesel?

Concerning the petrol-electric hybrid configuration Lexus believes it to be the most market viable alternative currently.

Hydrogen systems have huge infrastructure inefficiencies – they practically don’t exist in most of the developing world – and diesel is seemingly at the Bell curve turning point in its balance between power, efficiency and particulate emission volumes.

In a South African context the prevalence of low-grade diesel – especially in rural areas where one inevitable is forced to fill-up at odd hours during marathon drives – serves as a further barrier to diesel-hybrid deployment.

Add to this the intense forces necessary to start a compression ignition engine (compared to petrol), and the severe accompanying torque and vibration characteristics, and it’s clear an electric hybrid drive system, which continuously dovetails between internal combustion and electric drive, is incommensurable with diesel.

Self sustaining

Both GS and RX hybrids employ petrol V6 power with double-overhead camshafts and dual VVT-i valve timing and lift technology. The GS 3.5l V6 produces 218kW and 368Nm and the RX 3.3l engine 155kW and 288Nm.

Augmenting the petrol engines are Lexus hybrid electric motors of a compact, permanent magnet type design benefiting from both water and oil cooling.

Numerically the AC synchronous motor adds 147kW and 275Nm to the standard drivetrain of the GS. The RX features two electric motors, one adding 123kW and 333Nm to the front wheels while the second unit enables 50kW of power and 130Nm or torque on the rear axle when all-wheel capability is necessitated.
Charging of the batteries is accomplished in two ways, both vehicle dynamic sources. The electric motor captures kinetic energy harnessed by the sheer momentum of either the GS (1930KG) or RX (2000KG) in motion when on overrun or braking to recharge the Nickel hydride batteries. The 650V motor is managed by a Power Control Unit (PCU).

When necessary the batteries are recharged by drive off the petrol engine itself and you can watch the entire interaction on a drivetrain configuration display screen.

Both GS and RX start in electric mode with the PCU initiating the internal combustion engine as demand for more power and torque increases with throttle position or speed (to overcome drag or road gradient).

Stop-start internal combustion efficiency technology is incorporated too, as the PCU automatically switches off the internal combustion engine at low speed, especially when negotiating stop-start traffic.

Power not quite by the numbers

There are a few technical issues worth clarifying. Firstly, the power and torque figures are supplemental between the V6 and electric drive system; you cannot calculate a combined peak power or torque figure by adding the numbers.

In real world driving the PCU dovetails the internal combustion element and electric motor continuously, ensuring there is never a maximum combined output.

This is the reason you forego a rev counter in favour of a power output dial calibrated to a maximum of 250kW in the GS and 200kW in the RX instrument binnacle – though combined on-paper engine/eclectic output is 328kW for a RX and 365kW for a GS is you simply added the figures.

The other hybrid drive issue concerns battery life. In absolute terms the batteries are guaranteed for three years and should survive the lifecycle of the car, while on a day-to-day basis the intricate PCU system ensures they never run flat.

Does it work?

Beyond the impressive on-paper figures and technological novelty the key questions remains whether the Lexus hybrid drive systems actually deliver on their promise locally. The answers are oddly conflicting.

We spent two days hammering the cars in a very uneconomical style around Mpumalanga – blame the fabulous driving roads and lack of weekend traffic – and the conclusion I reached was counter intuitive.

The hybrid drive GS and RX are negligibly more efficient than a comparable turbodiesel.

Lexus claims 7.9l/100km average consumption for the GS and 8.1l/100km; but these are fairytale, control condition numbers. We averaged 14.3l/100km in the GS and 12.6l/100km in the RX and the reason for this was simply the unbelievable cruising pace the hybrid drive system engages you to sustain.

Juvenile accelerations figures are hugely impressive with the GS dispatching 0-100km in 5.9 seconds and the RX running it in 7.3 second. A more real-world unit of analysis is the 30-80km/h acceleration in 3.5 second and 3.9 seconds respectively for the GS and RX.

At first the drive system is odd; making a fool of me as I switched the GS on and off four times in the hotel parking lot; oblivious to the pre-drive briefing detailing the electric power only start-up-and go operation.

You push the start button; receive a ‘ready’ instrument binnacle signal, slot it into gear and move off on a 275Nm wave of silent torque. Professional assassins the world over; this is the car you have been waiting for…

As you pick up pace the V6 petrol engine come online, but overall the lack of mechanical noise, especially under harsh overtaking acceleration, is eerie.

Cruising speeds of 160km/h are achieved in uncanny refinement; you start noticing tyre noise levels usually inaudible in a normal car. The CVT gearbox on both cars fuses the petrol and electric power curves seamlessly, and it's by far the best adaptation of CVT technology I've driven to date.

Of the two hybrid powered vehicles I preferred the RX; it has infinitely better seats (the GS is cursed with flat-slap American spec items up front) and the RX foot operated parking brake is not hinged as low down in the footwell as the GS either, where it constantly irritates.

In mitigation the GS, with is longitudinally mounted V6, is marginally quieter overall than the RX which has its V6 transversely mounted.

Both cars have slightly over-assisted rack-and-pinion electric power steering, with the GS riding on a double-wishbone suspension set-up all-round, boosted with adaptive control. RX is also independently suspended all-round, but features MacPherson struts.

Though the hybrid drivetrain comes at no additional service or operational costs – service intervals remain the same as other Lexus GS/RX models and there’s the four year/100 000km maintenance plan too – is does incur a pretty severe boot space penalty in the GS.

Whereas the standard GS range has a capacious 430l boot, the GS450h sees its golf club carrying capacity truncated severely to only 280l. The RX suffers no reduction in luggage carrying capacity, and both cars are equipped with a full-sized spare wheel.

The future is now?

Both the GS450h and RX400h are curious cars. A comparable German turbodiesel premium sedan or SUV will match them in overall consumption figures.

Concerning overall driveability though, the hybrids dispel any Prius comparisons. They are both absurdly swift cars, able to cruise at high speed with very low noise levels and reserve overtaking verve easily comparable to a premium class German V8 sedan or SUV.

If the idea of running your premium sedan on putrid local quality diesel does not appeal, and you yearn for some refined, premium cruising capability the GS450h and RX400h should appeal strongly.

The interior materials and design of both cars lack the kudos of their German rivals, but they have electric everything, reversing camera capability and satnav. Both GS450h and RX400h are in fact so comprehensively specced there are no optional extras...

In broader terms though, these cars represent a critical juncture in automotive history. Its all fine and well producing exotic hybrid concepts, another case altogether to ship them to dealers for sale to real world customers.

I expect those willing to pay the significant premium will not be disappointed in dynamic terms, though the significant performance reserves tempt one into adapting a distinctly enthusiastic driving style, defeating the traditional, low-consumption raison d'etre of a hybrid.

The Lexus hybrids are a noble novelty. They’ll make a significant statement at the local country club; showcasing a blend of moneyed style and performance orientated indulgence without any environmental malaise. When emissions tax arrived locally they'll make a lot more sense as a financial decision too...

On a Rand-for-Rand basis running a comparable turbodiesel in the short term would probably be cheaper, though the Lexus vehicles come loaded with kit compared their German rivals.

Saving the polar bears was never supposed to be this swift or stylish.

Thanks to Lexus it is. They deserve a corporate halo of sorts.


RX400h R644 900
GS450h R586 100
GS450h SE R635 000


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