Overview: Lexus CT200h
The Lexus CT200h is the first full hybrid vehicle to be launched in the premium compact segment. As such, it has some significance. C-segment cars represent an important part of the market, and the ‘prestige’ manufacturers are already there with various conventional vehicles: Audi, BMW and Mercedes-Benz already offer small cars; there is a new small Saab on the way, and Volvo’s existing C30 has its own niche in the C-segment. Owners of larger cars are opting for more economical models, and drivers who have previously bought cars from mainstream manufacturers look up to marques like Lexus. With Mercedes-Benz still a long way from production with its B-class F-cell, the CT200h is the first car to be sold in this category with an unconventional drivetrain.
The newcomer is a full series-parallel hybrid and thus technically complex, yet it is still the entry model to the Lexus range. Lexus hopes that it will attract new, younger customers to the brand. The CT200h was designed and developed specifically with the European market in mind. Audi’s A3 and BMW’s Einser are the obvious targets: its wheelbase of 2600mm compares with the Audi’s 2578mm and the Bavarian’s 2660mm.
The production-ready CT200h retains strong visual links to the LF-Ch show car that appeared at last year’s Frankfurt motor show.
The Lexus Hybrid Drive system in the CT200h is, of course, a transplant of Toyota’s Hybrid Synergy Drive system. The 1.8-litre petrol engine combines with an electric motor in a series-parallel drivetrain: the car can be driven by either power unit individually, or by both together. Unfortunately, like the Prius, performance under electric power is rather limited by the cars’ modest nickel hydride battery pack: the range is 1.2 miles, the maximum speed 28mph.
The petrol engine operates on a pseudo-Atkinson cycle, in which the expansion ratio is greater than the compression ratio. This is achieved by leaving the intake valves open for the first few degrees of the piston’s upward stroke. A power split device combines power from the petrol engine and the electric motor-generator, and to the motor-generator on overrun, as driving conditions demand. Drive torque is transmitted to the wheels through an electronically controlled CVT.
Drivers have the choice of four selectable drive modes: Normal, E.V., Eco and Sport.
From start-up and at speeds below 28mph, the CT200h automatically operates in E.V. mode; the driver can also select E.V. mode manually. When the car reaches the limit of its range under electric power, or exceeds 28mph, the petrol engine is automatically started.
In Eco mode, response to accelerator pedal input is softened and the air conditioning control is adjusted to maximise fuel economy.
Sport mode is designed to deliver extra electric motor power, with the supply voltage boosted by 150V to a maximum 650V. Higher crankshaft speeds are used, and the throttle and electric power steering (EPS) settings are adjusted for quicker response and extra feedback. Operation of the traction control and Vehicle Stability Control (VSC) is also rendered less intrusive.
The CT200h is built on a new platform with a dedicated double wishbone and trailing arm rear suspension system. A McPherson strut set-up is used at the front. The double wishbone rear assembly is exclusive to the CT200h and incorporates a lightweight trailing arm. The springs and dampers are positioned separately to minimise intrusion into the loadspace. Apparently to counter vibration, Lexus has designed an optional lateral performance damper system: used in place of fixed bracing, this feature deploys horizontal dampers located between the front suspension towers and the left and right sides of the rear structural frame.
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Power steering is electric, with the motor powered by the hybrid powertrain’s NiMH battery-pack. Some better-specified CT200h models will come with double LED dipped-beam headlight units.
Inside, the instrument binnacle houses two large dials. In Sport mode, the hybrid indicator in the binnacle turns into a rev-counter and — an extraordinarily naff feature — the ambient lighting turns from blue to red. The two-mode switch ring and a spotlight in the centre cluster also light up in red. Ho hum.
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series & parallel