2013 GS 450h EPA-rated at 31 mpg combined; 35% improvement over preceding generation

2013 Lexus GS 450h. Click to enlarge.

Lexus’s 2013 GS 450h—the new generation hybrid version of the GS 350, introduced at the 2011 Frankfurt Motor Show (earlier post)—offers EPA-estimated fuel economy ratings of 29 mpg US city, 34 mpg US highway and 31 mpg US combined (7.7, 6.9 and 7.6 L/100km, respectively).

These figures represent a 32%, 36% and 35% improvement in fuel economy, respectively, compared to the prior generation of the GS 450h (e.g., MY 2011). These figures also represent a 53%, 21% and 35% improvement in fuel economy, respectively, compared with the conventional 2013 GS 350. (As a side note, the combined cycle fuel economy of the conventional 2013 GS 350 is now the same as the combined cycle fuel economy was for the earlier version of the GS 450h hybrid.)

The second generation of the Lexus Hybrid Drive system applied in the new GS 450h features a next-generation D-4S direct and port fuel injection system with an Atkinson cycle 3.5-liter V6 engine mated to a compact, high-output, water-cooled permanent magnet electric motor powered by a high performance NiMH battery pack. The two powerplants drive the rear wheels both independently and in tandem, as needed. Total system output is 338 hp (252 kW).

Features of the powertrain include:

• Improved fuel consumption is achieved through a high compression ratio of 13:1, a new mid-port intake tumble generator and the adoption of a Lexus four-stroke, direct injection technology, D-4S.
• 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 NVH characteristics.
• 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 DC/DC converter.
• 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 system’s regenerative braking operation range has been expanded, contributing to further improvements in fuel efficiency.
• A new stacked battery configuration maximizing luggage space allows the 2013 GS 450h to have more cargo area than the previous generation GS 350.
• Acceleration from 0-60 mph in 5.6 seconds.
• Super-Ultra Low Emissions Vehicle (SULEV) certification.
• Engine noise, vibration and friction have been lowered through the adoption of lightweight timing chain technology.

The GS 450h has five driving modes that can be operated by toggling the new Lexus Drive Mode selector. In addition to the Normal mode, the following settings let the driver customize the driving experience:

• ECO mode revises throttle mapping, seat heating, and climate control systems for better fuel economy. In ECO mode, meter lighting changes to blue.
• EV mode allows the vehicle to be driven short distances, under certain circumstances, using only the electric motors.
• SPORT S mode revises throttle mapping and transmission shifting priorities to fully exploit the capabilities of the powertrain. In SPORT S mode, meter lighting changes to red.
• SPORT S+ mode engages handling enhancements via a sport setting of the adaptive variable suspension, steering system, and Vehicle Dynamic Integrated Management (VDIM) together with the powertrain enhancements of SPORT S mode.
  
  
  
  
  Source: Green Car Congress