lexus gs 450h 2012-2013 review:
As with all Lexus hybrid vehicles, the new Lexus GS 450h is a full hybrid capable of operating in gas-only or electric-only modes, as well as a combination of both. Its Lexus Hybrid Drive system features an ultra-smooth running, Atkinson cycle 3.5-liter V6 engine mated to a compact, high-output, water-cooled permanent magnet electric motor. The two powerplants drive the rear wheels both independently and in tandem, as needed.
In addition to the gas engine and electric motor, the new GS 450h's hybrid drive system a generator; a high-performance nickel-metal hydride battery; a power split device which, via planetary reduction gears, combines and re-allocates power from the engine, electric motor and generator according to operational requirements; and a compact power control unit to govern the high speed interaction of the system components.
Adapted specifically for the hybrid powertrain and a first for premium performance sedans, the 3.5-liter V6, DOHC engine benefits from several technical improvements including the adoption of the Atkinson Cycle engine design to optimize the fuel-efficient benefits of Lexus Hybrid Drive.
Compression is delayed in an Atkinson Cycle engine, because the intake valves close late. This creates a high expansion ratio for less compression, reducing intake and exhaust energy losses and converting combustion energy to engine power more effectively.
A high compression ratio of 13:1; a new, mid-port intake tumble generator; and the adoption of the latest evolution of Lexus' four-stroke, direct injection technology, D-4S, help the Lexus GS 450h achieve better fuel consumption.
With one injector installed in the combustion chamber and a second mounted in the intake port, D-4S combines the strengths of both direct and port injection, realizing optimum engine efficiency throughout the power band and improving torque across the rev range, while minimizing fuel consumption and emissions.
The D-4S system features new slit-type injector nozzles with a modified port shape, a higher fuel pressure for more efficient combustion, and idle port injection for improved NHV characteristics.
Engine noise, vibration and friction have been lowered through the adoption of lightweight chain technology.
The cooling performance of the hybrid system's Power Control Unit (PCU) helps reduce fuel consumption and has been improved through the adoption of dual cooling paths and a single-piece, integrated AC/DC converter.
System control has been enhanced. The PCU boosts motor drive voltage to a maximum 650V in Sport mode and limits it to a maximum of 500V in Eco mode under normal driving conditions where maximum output is not required. The motor is driven at lower voltage to provide a more environmentally-advanced driving performance to help enhance fuel efficiency.
The electric motor features lighter mounts and reduced friction. The system's regenerative braking operation range has been expanded, contributing to further improvements in fuel efficiency. In addition, the battery layout has been redesigned. A new stacked configuration maximizing luggage space allows the 2013 GS 450h to have more cargo area than the previous generation gas model.
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