2011 Porsche Cayenne S Hybrid Full Test

The 2011 Porsche Cayenne S Hybrid is dead quiet as it waits on the Inside Line test track, its start-stop mode engaged. Throttle wooded, the hybrid Cayenne's electric motor hums to life, and a fraction of a second later, the shrill roar of the supercharged, direct-injected V6 fills the air.

Only then does the Porsche Cayenne Hybrid punch a hole through the morning haze. Along the way, it sounds like the nicest, most expensive vacuum cleaner we could ever hope to own. Still, the 2011 Porsche Cayenne S Hybrid is quicker and more engaging than any other hybrid SUVs we've ever tested, which is an admittedly low bar.

The real question, then, is not whether you'd buy a Cayenne Hybrid over a cheaper, less personable Lexus RX 450h, but whether you'd choose it over any of the other 2011 Porsche Cayennes.

We Took Out 300 Pounds, Then We Put Them Back
Porsche started work on the hybrid Cayenne six years ago (and indeed we drove a prototype with the old bodywork), but the automaker waited for the SUV's 2011 redesign before rolling out the production version. This was a wise move, because the Cayenne S Hybrid would have weighed 3 tons on the original leaden chassis.

The new unit-body is 150 pounds lighter, and altogether the base Cayenne V6 and V8-equipped Cayenne S weigh 300 pounds less than their 2010 counterparts.

Of course, the hybrid components add back all that weight, but at 5,165 pounds, our 2011 Porsche Cayenne S Hybrid test vehicle is just 50 pounds heavier than the last Cayenne Turbo we tested. So there's that.

Like a Honda, But Better
As hybrids go, the Cayenne Hybrid is pretty simple. Like all Honda hybrids to date, it's a parallel hybrid. There's a 47-horsepower electric motor sandwiched between the longitudinally mounted, supercharged, 3.0-liter V6 and an eight-speed automatic transmission that drives all four wheels through a conventional all-wheel-drive system. A nickel-metal hydride battery pack is mounted behind the rear axle.

But Porsche has gone one better than Honda by fitting a clutch between the 333-hp V6 and the electric motor. The clutch fully disengages the engine during electric-only operation and coasting, rather than allowing the pistons and crankshaft to keep cycling, and this reduces frictional losses. (On Honda hybrids, only the engine's valves close.)

The hybrid system's clumsy management of regenerative braking is unacceptable at this price.

What makes the 2011 Porsche Cayenne S Hybrid different from series-parallel hybrids like the Prius and RX 450h is that it can't operate its gas V6 and electric motor at different rpm and blend them together for maximum fuel economy benefit. To do that, the Cayenne would need a second electric motor and a continuously variable transmission. This approach would have cost more and risked an un-Porsche-like driving experience.

Quick When It Has a Full Charge
Although it's technically possible to drive the hybrid Porsche Cayenne on electric power alone up to 37 mph, it requires tiny throttle inputs and considerable patience from other motorists.

Mostly, the electric motor is just an assist for the V6, and when the batteries have a full charge, this combination (380 total hp and 427 pound-feet of torque) delivers you to 60 mph in 6.1 seconds (5.9 seconds with 1 foot of rollout as on a drag strip) and has you at the quarter-mile mark in 14.5 seconds at 93.9 mph. Among hybrid SUVs, only the V8-equipped BMW ActiveHybrid X6 (claimed 5.4-second 0-60 time) could beat those numbers. For comparison, the RX 450h takes 7.6 seconds to reach 60 and 15.6 for the quarter-mile, while the Cayenne Turbo is on a different planet (4.6 and 12.8, respectively).

The battery charge depletes quickly, though, and on Interstate 5's Tejon Pass, the Cayenne's V6 feels pretty ordinary and sounds as if it would rather be motivating a tractor. The eight-speed automatic, though, is always on its game, moving between gears so deftly that we barely notice shifts. The transmission's sharpness also keeps us from being annoyed by its aggressive overdrive gearing, which has the engine at 1,800 rpm at 70 mph.

This, along with the Cayenne Hybrid's ability to shut off its engine when coasting at up to 97 mph, explains why the hybrid Porsche is rated at 24 mpg on the highway versus just 20 mpg in the city. We easily lay down a 24.2-mph highway-only tank, and on our city-intensive fuel economy loop, we get 23.2 mpg. Our average over 1,400 miles is 21 mpg.

Make It or Brake It
Parallel hybrid systems can be clumsy when transitioning between power sources, but the 2011 Porsche Cayenne S Hybrid's clutch-type system is smoother than most. When you're coming off coasting mode, it uses the electric motor to get the V6 up to the appropriate rpm.

Unfortunately, it isn't nearly as coordinated at managing the transition between regenerative braking and the normal, friction brakes. The small battery pack is again a factor, as it's continually in need of a top-up. When slowing in city traffic, a wave of regenerative braking takes hold abruptly, and it's hard to predict when it will let go and give us back the real brakes. The more we try to be smooth, the worse it gets. We're still apologizing to our woozy passengers.

Braking from higher speeds feels far more natural, as the hybrid Cayenne's conventional brakes grab immediately. This SUV has large six-piston front calipers squeezing 14-inch discs, along with four-pot rear calipers and 13-inch rear discs. Its 60-mph-to-0 braking distance is merely average at 120 feet, though, as its low-rolling-resistance Michelin Latitude Tour HP265/50R19 tires don't give it much grip.

A Cayenne in All Other Respects
Yet, those same tires contribute to the Porsche Cayenne Hybrid's very livable ride quality. Air springs and adaptive dampers with driver-selectable Comfort, Normal and Sport settings are standard on the hybrid Cayenne, and the Normal setting is just the right blend of compliance and control.

Sport is our choice on solo drives, as it makes this heavy SUV feel a bit more buttoned-down around corners. Its slalom (64.2 mph) and skid pad (0.87g) numbers fall well short of the Cayenne Turbo (67.0 mph, 0.94g), which had 295/30R21 tires and a penchant for defying physics.

The 2011 Porsche Cayenne S Hybrid's variable-ratio steering is the automaker's first application of an electric-motor-driven hydraulic pump. It's a lighter setup than you might expect from Porsche, but considering the modest tires, there's a surprising amount of steering feel.

Inside, the 2011 Porsche Cayenne Hybrid is as elegant as every other Cayenne we've ever driven. It certainly helps that ours has the full leather option, with real hide stitched onto the dash and doors. Porsche has always made a point of furnishing its SUV to a richer standard than any BMW, Benz or Land Rover. It's obvious here.

The familiar left-side ignition and center-mounted analog tachometer remain in the hybrid Cayenne, though there's an option to watch a hybrid energy flow display if you find that more interesting.

Needs Fine-Tuning
As we drive the 2011 Porsche Cayenne S Hybrid, there's little doubt that the 2011 redesign of the entire Cayenne line is a success. The ride and handling balance is spot-on, even on the hybrid model, and the updated cabin now has a backseat sized for adults.

That said, the case for the Cayenne Hybrid is not clear-cut.

Acceleration is certainly respectable, and there's a definite fuel economy benefit, as other 2011 Porsche Cayennes are rated at just 15-16 mpg in city driving. But the supercharged 3.0-liter V6 is noisy and devoid of charm, and while that might be OK in the $61,000 Touareg Hybrid, it's tough to take in a Porsche that starts at $68,675. Even more so in our tester that carries an $86,510 sticker.

Moreover, the hybrid system's clumsy management of regenerative braking is unacceptable at this price. It kills any appeal the Cayenne Hybrid might have over the slightly less expensive V8-powered Cayenne S.

Porsche's engineers need to put their heads together on this one, preferably before the 2012 Panamera Hybrid sets sail. We have a feeling that Cayenne buyers might be willing to put up with finicky brakes. We doubt Panamera buyers will do the same.

The manufacturer provided Edmunds this vehicle for the purposes of evaluation.