2013 Lexus GS 450h first drive: A hybrid? Could have fooled us.

2013 Lexus GS450h

2013 Lexus GS450h in the infield at Phoenix International Raceway

We’ll confess that we didn’t look to see exactly which 2013 Lexus GS we had jumped into before we buckled up and headed out onto the infield road course at Phoenix International Raceway. Nor when we put the hammer down. Nor when we clipped the corners and ran the inside tires up over the ramp-type curbs only to have the tires to return to earth, the Lexus GS wholly unperturbed.

It was only after we exited the car that we noticed on the car’s flanks a small badge that said “hybrid.”

Yes, we had just been circulating the course in a 2013 Lexus GS 450h. Powered by a gasoline-fueled 3.5-liter Atkinson-cycle V-6 rated at 286 horsepower paired with a pair of 650 volt electric motors, one with a power rating of 200 horses that teams with the gas engine to drive the rear wheels. The other has a 180 horsepower rating and it serves as the primary generator, engine starter and engine speed control.

The peak hybrid power system output—because the electric motor and the gasoline engine peak at different speeds—is 338 horsepower. It’s enough to launch the GS 450h from 0-60 mph in 5.6 seconds. And that’s a tick quicker than the standard Lexus GS350. And is has a EPA fuel consumption estimate of 29 mpg city/34 mpg highway and 31 mpg combined. Not, of course, the way we were driving, and it won’t arrive in Lexus dealerships until spring.

The 2013 Lexus GS 450h is a member of the all-new four generation of the Lexus GS family. Arriving in February are the base 2013 Lexus GS350 and GS350 Luxury, and the Lexus GS35- F Sport, scheduled for February. Both the base and Luxury models are available with all-wheel drive. All of the non-hybrid models are powered by the same rear-drive 306-horsepower 3.5-liter V-6 engine and oddly enough in this time of rapidly multiplying transmission ratios, with an only six-speed automatic transmission.

The engine is impressive, however, not only with variable valve timing but also with a combination port/direct fuel injection, which Lexus has dubbed D-4S. Lexus gives the fuel injection system credit for fuel economy and low emissions. The compression ratio, a proxy for the thermal efficiency of the engine, is a high 11.8:1. Without the charge-cooling effect of injecting fuel directly into the combustion chambers such a compression ratio is not possible. The conventional port fuel injection is retained primarily for idle operation where it’s has lower noise and vibration than direct injection.

The engine for the 2013 Lexus GS 450h is based on the conventional Lexus 3.5-liter engine but the Atkinson cycle system reduces pumping losses of the conventional Otto cycle thanks to the altered cam timing achieves a thermal efficiency—and therefore fuel economy—of 12-14 percent. The Atkinson-cycle engine has a compression ratio of 13.0:1.

Instead of the continuously variable-type transmission of the Toyota Prius, the 2013 GS 450h has a conventional automatic transmission which gives the GS450h the sound and feel of a traditional drivetrain. The two motors of the hybrid drive are incorporated into the transmission case with the main drive motor capable of moving the car alone without gasoline engine.

Compared to the previous generation of Lexus GS 450h, the battery pack has been downsized with a two-tier construction, with six modules on top and 34 on the bottom and along with the relocation of other elements allows a larger trunk volume.

The 2013 Lexus GS models have a new “first” for Lexus: a true dual exhaust system, from the engine all the way back to the rear of the car. For the GS450h, however, Lexus pretends that the engine has no exhaust, with the exhaust outlets hidden. That’s simply odd.

More than just powertrain, the 2013 Lexus GS 450h has an all-new chassis with a design feature that’s a precursor to future Lexus design. Lexus calls it the “spindle” grille. It’s an hourglass shape that actually looks better than it sounds and even better in person than in pictures. With the GS at least, there’s function to follow the form. The large slots in the “cheeks” are ducts that blow cooling air directly onto the front brake discs, unlike the dogleg ducts of the previous generation.

Lexus has installed nearly a full belly pan under the GS, not only for reduced drag from the air passing beneath the car, but Lexus has also added vertical “aero-stabilizing” fins to direct and smooth the airflow.

The body is stronger and lighter for the 2013 Lexus GS models. Rather than aluminum for lightness, just over 40 percent of body mass is high-tensile steel sheet and hot pressed steel. The latter is steel so stiff that it can’t be shaped with normal cold stamping. Instead the steel has to be heated (using electric current) to stamp it into the desired shape. It’s used maintain strength between the B-pillar and the roof side rails with a simpler structure that can be lighter in weight.

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