Bionic cheetah gives chase to Porsche SUV.

Introduction

The new Infiniti FX45 is quicker than Porsche's new Cayenne S. Specifically, the FX45 can zip from 0 to 60 mph in slightly more than 6 seconds, while the Porsche Cayenne S takes a bit longer. 

How can that be? Though the Porsche is more powerful, the Infiniti has a better power to weight ratio. The 315-horsepower Infiniti FX45 weighs about 600 pounds less than the 340-horsepower Porsche Cayenne S. Do the math. (Actually, we'll do it for you: The 4,949-lb. Porsche uses 1 hp per 14.5 lbs.; the 4300-lb. Infiniti has 1 hp per 13.6 lbs.) Infiniti claims the FX45 is quicker than the other hot-rod SUVs, namely the Mercedes M55 AMG and the BMW X5 4.6is. 

At the same time, the Infiniti models cost less than their German counterparts. 

These performance and pricing advantages come partly by making a conscious decision that Infiniti's new luxury sport-utilities would not be designed to go off-roading. Therefore, the FX45 frame could be lighter, lightening the load for the Infiniti V8. 

The weight advantage was just a starting point, however. Infiniti added enormous 20-inch wheels and tires and racecar-sized brakes. Infiniti's goal was to make the FX45 as fun to drive as a sports car. It achieves this by compromising in ride comfort, space and rock-climbing ability. The end result is a car-based crossover SUV that's exciting to drive on sports car roads and full of character, but has a stiff suspension and ride, a tight cockpit, and flamboyant styling. 

Squeezing into the cockpit and bouncing along a bumpy snow-belt backroad in the FX45 will appeal only to confirmed sports car enthusiasts. Infiniti expects to sell just 30,000 per year, while BMW last year sold about 43,000 X5s. 

The suspension reflects Infiniti's decision not to make the FX an off-roader: Generally off-road ability is enhanced with long-travel and compliant suspension tuning, but that same ability compromises handling on winding roads. FX is tuned for those winding roads, and despite its tall 7.6-inches of ground clearance, it has no skid plates or underside armor. FX is based on the same Front-Mid engine platform used for the Nissan 350Z sports car and Infiniti G35. Thicker frame members make FX strong enough to handle the extra weight of the bigger four-door wagon body. 

Marketing played a role in the FX's pure pavement identity: Infiniti doesn't believe anyone who spends up to $50,000 for a crossover SUV will risk scratching it in the dirt. 

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Lineup

Two models are available: Infiniti FX35 ($34,200) is powered by the 3.5-liter V6 from the Nissan 350Z. FX45 ($44,225) gets the 4.5-liter V8 from the Q45 luxury sedan. 

Both come with a five-speed automatic transmission, dual-zone climate control, power front seats, split folding and reclining rear seats, tilt/telescope steering wheel, traction control, stability control, brake assist, and high-intensity discharge headlights. 

FX45 gets a firmer suspension, 20-inch wheels, leather heated seats and trim, power tilt/telescope steering wheel, memory for seat, mirrors, and steering wheel, auto up/down windows. FX35 offers those items in its a Premium Package ($2,600), which also includes a sunroof, a more-powerful stereo with controls on the steering wheel, automatic headlights, and a garage door transmitter. You can add the last four items to the FX45 in a Premium Package ($2,100). 

Both models offer a Technology Package that includes all of the options in the Premium Packages, plus a navigation system, a remote sensing door key, traffic-sensing cruise control, a DVD system, a rear facing camera to assist backing up, and a tire pressure monitor. The Technology Package for the FX35 also adds the 20-inch wheels and the stiffer suspension, and costs $9,400 on top of the FX35's base price; the package adds $7,600 to the FX45's base price. Roof rails are available for $300 on cars with the Premium Package and satellite radio is $400. 

Only a third of Infiniti SUV buyers are expected to buy the FX45. A lower-priced V6-powered FX35 starts at $34,200 in rear-drive-only form, though only about 14 percent of buyers are not expected to get the $1500 all-wheel-drive system that's available on the FX35 and standard on the FX45. 

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Walkaround

You might not notice the curvy body of the FX45 because the enormous wheels attract most of your immediate attention. BMW's hottest X5 also comes with 20-inch wheels, but on the curvy Infiniti the wheels look disproportionately larger. The FX35 comes standard with 18-inch wheels, which are also larger than what you'll find on most SUVs. Once you get used to the monster wheels, the curved body takes your attention. 

Infiniti says the FX is supposed to look like a sports car from the beltline up. A big grille greets oncoming traffic, but the bulging hood looks high to us: A peek underneath the hood of the FX45 shows the big V8 is tucked far down below. 

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Interior

When you climb into the driver's seat, you're coddled by the console and instrument panel, and it feels like a tighter fit than you'll find in most other SUVs. 

The front seat is adjustable for height with 3 inches of vertical travel, so you can choose to perch up high to keep tabs on the rest of the tall SUV commuters around you, or you can drop your hind end down to the floor for serious driving on challenging pavement. The view over the hood reminds us of a Jaguar's or a Porsche Cayenne's, with a hood contoured over the headlights and grille. It's the opposite look of the squared-off hood of a BMW X5 or Range Rover, and the view keeps telling you you're in a car, not a truck. 

The view out the back is not hindered by the sloping D-pillar, although an optional rear-view camera, like you'll find on big motor homes, will display a rear view on the 7-inch dashboard monitor. The rear display shows two virtual lines on the rear image that correspond to the width of the FX. We still didn't trust it when parallel parking, but we suspect some FX owners will learn to. 

The steering wheel and gauges remind us of the Nissan 350Z's with a thick rim framing big dials. The gauge pod adjusts with the tilt wheel. Given this sports car climate, we expected to find a six-speed manual shifter in the FX, but a five-speed automatic is the only gearbox available. Infiniti, however, says they haven't ruled out offering a manual in the future. 

Three adults fit comfortably in the split reclining rear seats, which we didn't expect with the sloping rear roof. Total rear cargo area is smaller than in square-shaped SUVs. Infiniti says it placed a higher priority on floor space and that the FX offers more floor space than a BMW X5 or a Lexus RX300. 

FX45's optional Bose 300-watt 11-speaker stereo was tuned for the middle-aged mid-life crisis male. Infiniti says it worked with Bose specifically to get the car to play rock and roll. Bass and treble were emphasized. Satellite radio service is optional, too. 

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Driving Impression

Plant the accelerator onto the floor of the Infiniti FX45 and you'll be rewarded with a healthy hot-rod roar. As revs rise, the sound becomes a higher-pitched hum. The brisk acceleration of the big FX makes it feel athletic and nimble, and you get the feeling you can pass anything in your way. 

The FX35 launches impressively from a stop, likely because its 280-horsepower V6 makes 270 pounds-feet of torque at 4800 rpm, the same as the 350Z sports car and substantially more than other V6 SUVs. Approaching higher speeds, the 315-hp FX45 pulls more strongly than the FX35. The price for this performance is 15 mpg on the EPA's city cycle, while the V6 model returns 16 mpg. Top speed in both models is governed to 130 mph. 

All of this power is managed with sophistication: The available all-wheel-drive system is tuned for paved roads. All power is sent to the rear wheels until slip is detected, and then it is gradually transferred to the front wheels. You can manually lock the front and rear axles together, or you can let the electronics do it for you. The standard electronic stability controls, which brake individual wheels to control vehicle attitude, engage so gradually we couldn't detect when they were working. That means the driver makes the big decisions, such as entry speeds into a corner, and the car decides the little things, such as the optimum braking for each wheel to keep the car doing what the driver wants. 

Driving our FX45 test car on the twisty two-lane sports car roads circling the Red and Black Mountains in Southern California, we were still able to induce a slight amount of power oversteer while cornering, although we were never able to break the mammoth rear tires loose. 

In tight and sweeping corners alike, the FX45 rode incredibly flat, which is the plus side of having such a stiff suspension. We pushed the FX45 hard, and didn't give it a break because it was an SUV. Understeer begins very gradually when you aim the FX into a corner, and the front wheels continue to push only slightly until you get near the FX's very high limits. Like the 350Z sports car, the steering is quick, but it doesn't feel as telepathic as a Porsche's. Nor does it feel like the light-and-loose feeling you'll experience in any other SUV, including BMW's X5. 

Infiniti claims the FX will brake better than rivals from Mercedes, BMW, and even Porsche. Our FX45 test car was confident under heavy braking, and that allowed us to drive it very quickly without any scary moments on twisty roads, but there's no question there's a lot of size and weight here. 

Our FX45 was as much fun to drive as most sport sedans, but the price is the stiff ride. On long stretches of freeway, the FX45 is relaxed, and our test car cruised at 80 mph in fifth gear with the engine turning just 2850 rpm. Our FX45 wasn't as quiet and isolated as some luxury cars, and although our test car's cockpit was quiet enough to hold a delicate cell phone conversation on an empty highway, we'd never describe it as a serene environment. 

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Summary

The all-new Infiniti FX is an active-participation machine, not a chamber away from the real world. It offers plenty of confidence in its ability driven quickly. Its acceleration and braking set new standards in performance for SUVs. The suspension tuning of the FX45 is on the firm side. 

To go with the advanced SUV capabilities, at least on pavement, the FX offers luxury toys such as a rear-view camera, an amazing stereo, a DVD video player for rear-seaters, a cruise control that senses traffic ahead, state-of-the-art stability and braking controls, and a door key that automatically unlocks the doors when you approach the car. 

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Model Lineup

FX35 RWD ($34,200); FX35 AWD ($35,700); FX45 AWD ($44,225). 

Assembled In

Kanagawa, Japan. 

Options As Tested

V8 Technology Package ($7,600) includes remote automatically unlocking door key, traffic-sensing cruise control, navigation system, DVD player, rear-view camera, tire-pressure monitor.