The new Infiniti is more generous under the hood, too. The M45's 335-horse, 4.5-liter moves with more authority than the GS's 300-horse, 4.3-liter, despite carrying 164 extra pounds and being down one gear to the Lexus's six-speed transmission. The Infiniti V-8 loves to rev and has a rich top end, blasting the M45 to 60 mph 0.3 second faster and down the quarter-mile 0.4 second faster than the GS 430. It's no surprise the Infiniti's 10 percent horsepower edge allows it to run away from the Lexus in acceleration tests, but the two company's different approaches to vehicle dynamics drive to the heart of their diverging brand identities.
With the upcoming Lexus GS gas/ electric hybrid just around the corner, engineers have developed electronic steering and braking systems that they've also applied to the GS 430. Electronic power steering bases the amount of boost on steering angle, vehicle speed and yaw rate. This is combined with vehicle-speed sensitive variable gear ratio steering, which among other algorithm-enhanced features has a built-in side-wind correction factor. The electronic brakes phone in the driver's commands to the calipers, but Lexus has seen fit to equip the GS 430 with high-friction pads, a combination that makes the brakes touchy and difficult to modulate because of their nonlinearity.

Lexus has a simpler, cleaner center stack approach, with large, readable touch screen.
Vehicle Dynamics Integrated Management is Lexus's fancy name for a combined stability control and electronic braking system that constantly monitors vehicle balance and anticipates situations rather than reacting to them. Lexus boasts that the system takes care of problems before they occur and is the root of our displeasure with this car. In sporty driving, the GS 430 often feels like a baby bird that won't leave the nest--safe and secure in its well-feathered domain, but will never know what it's like to soar.
In contrast, the M45 Sport hugs the road the old-fashioned way--with big, 19-inch meats and a well-calibrated suspension. Its active rear steering system, which gives a variable ratio by moving the toe links on the rear suspension, takes some getting used to. On decreasing-radius exit ramps, the M45's line tightens noticeably and the driver needs to adjust to the sharper turn-in. Stability control is far less aggressive than on the Lexus and can be switched off if desired. And there's no denying the effectiveness of the M45's conventional hydraulic Brembo brakes, which stop the heavier car some 15 feet--nearly one car-length--shorter than the electronically dithered-with Lexus from 60 mph.

Infiniti M45 Sport
If you drove only the GS 430, you'd probably come away impressed with its quiet and confident over-the-road performance. But take a stint back-to-back in the Infiniti M45 Sport, while muscle memory is still fresh, and it's clear the M is crisper, more entertaining and more satisfying in its responses, particularly if you value sportiness. Acceleration is more brisk, turn-in more responsive, braking far more direct, organic, and easier to modulate. The GS 430 is somewhat muted, insulated from what the road, the engine, and the car's other mechanical bits are doing. Its electronic overlords keep you from straying from the smooth and steady, abetting your innate driving abilities with a digitally enhanced reality. Beyond the performance numbers, the M45 Sport with its active rear steering toe links is more responsive in transitions.
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