Infiniti's performance Hybrid

Tired of being tied to Toyota's coattails in the hybrid race with its Toyota-licensed front-wheel-drive hybrid powertrain in the 2008 Nissan Altima Hybrid, Nissan has developed a rear-wheel-drive hybrid system of its own.

We drove the 2008 Infiniti G35 Hybrid Prototype at Nissan's proving ground in Oppama, near the seaport town of Yokohama, Japan, and it makes us think that a hybrid performance car from Infiniti could be in our future.

It's on the Way
While we tried out this system in a 2008 Infiniti G35 Prototype, this won't be the car Nissan finally introduces two years from now. We know, because Nissan's Minoru Shinohara, senior vice president of technical development, told us so. Of course, we wouldn't be a bit surprised to see a hybrid version of the Infiniti G37 sedan show up a year or so after the inaugural model makes its bow.

Nissan plans a "new model" for its first self-developed hybrid, Shinohara says. It is to be launched in the company's fiscal 2010, a 12-month period that spans the final three-quarters of 2010 and the first quarter of 2011.

It won't be the industry's first RWD hybrid — Toyota's Lexus brand captured the honor with the 2007 Lexus GS 450h. But it will be unmistakably a Nissan and express the brand's sporting, performance-oriented DNA, the Nissan executives emphasize.

This could be good, but Nissan ought to take a close look at Honda's attempt to stress performance over fuel economy with its short-lived Accord Hybrid (2005-'07). The car never caught on, not because it wasn't a good vehicle but instead because hybrid buyers at the time were chasing mpg, not mph.

Nissan execs, though, say they can bring both to the table with their new rear-wheel-drive system.

Expect a New Infiniti
If we were guessing — and we are — we'd anticipate that the first rear-wheel-drive hybrid from Nissan will appear not as a Nissan but as a new Infiniti model, since this is the brand that Nissan is using to promote its RWD platforms.

Shinohara and other Nissan executives and engineers at Oppama were pretty close-mouthed about specifics of the new rear-wheel-drive hybrid package. Among the things we don't know are the hybrid package's total horsepower and torque, estimated fuel economy or anticipated acceleration performance.

All Nissan would tell us at this stage is that the system is more powerful than a standard 306-horsepower 3.5-liter V6, but not as powerful as Nissan's 390-hp 5.0-liter V8.

The standard G35 scoots to 60 mph in about 5.6 seconds; we're guessing 5.4 seconds or less for the hybrid.

As for fuel economy, one engineer whispered something that sounded like Nissan thinks that the new hybrid could get 40 percent better mileage than a standard G35 sedan. This would lead us to expect about 24 mpg in the city and almost 34 mpg on the highway in a G35 sedan-size vehicle.

Truncated Test
The other thing we don't know much about is how Nissan's rear-wheel-drive hybrid system performs on the road. That's in part because we were driving a G35 hybrid prototype and not the new car itself. More important, Nissan only gave us about five minutes behind the wheel of the G35 mule, and we drove a tiny loop that was entirely flat and had no challenging corners.

The only time we tried to put our foot in it, our Nissan-assigned co-driver used what little English he had to politely say, "Slow, please. This is test car only."

All we can tell you is that when we goosed it, the G35 mule shot out of the blocks like a sprinter fleeing a doping test. With its V6 boosted by a powerful electric motor, the G35 with the new hybrid system is definitely quicker than the standard gas model. But it also stumbled and bucked at the critical junction of low-speed cruising and full-throttle acceleration, when the power-management computer was cycling the system between all-electric and gas-electric modes.

Nissan Hybrid Engineering Manager Tatsuo Abe acknowledged the problem, reminding us this was a "development vehicle" and that the system — especially the power control software — still needed refining.

Also in need of refining, he admitted, is the regenerative system that feeds power generated by braking into the battery pack to help top off its charge. The brakes shuddered as the system tried to transition between the regen system and the mechanical system, an issue with all regen braking systems that requires some fairly sophisticated development.

Lithium-Ion, No Plugs
Nissan didn't design the new hybrid to be a plug-in, saving that honor for its proposed battery-electric car that it also plans to bring out in 2010 in very limited numbers.

Instead the system uses excess energy generated while braking and at cruising speeds to charge up the specially developed lithium-ion battery pack, just like all of today's conventional hybrids. The battery packs weigh in at about 100 pounds apiece, and were developed by a company jointly controlled by Nissan and Japanese electronics giant NEC.

One version of the new battery design will be used in the all-electric car, optimized for energy density in order to provide acceptable range between charges. The hybrid will use a different design that packs more power at the expense of all-electric range.

Flat Is Cool
Nissan's battery engineers wouldn't reveal details, but said the new hybrid batteries will provide about twice the power density (power per kilogram of weight) of most existing lithium-ion batteries. That's what quickly provides the jolt of juice the electric motor needs in massive but short bursts when the driver stomps on the accelerator.

Unlike most lithium-ion cells that use cathode and anode layers rolled into a cylindrical shape like flashlight batteries, Nissan's are laminated and lay flat, a design that makes them easier to cool — a critical attribute to ensure both longevity and safety in heat-prone lithium-ion batteries. The flat shape also makes it easy to stack cells into compact modules that reduce weight.

Not So Simple
No hybrid system is simple, since it involves packing two complete power plants and lots of expensive electronic controls into one car. That's why hybrids today can cost thousands of dollars more than gas-only versions of the same model.

Nissan's is no exception, although its unique design does simplify the powertrain somewhat because it does away with the hefty torque converter that the seven-speed automatic transmission would otherwise require in a standard gasoline-only car.

A pair of clutches replaces the torque converter — a dry clutch between the engine and the transmission plus a wet clutch behind the electric motor at the end of the transmission case.

Four Modes of Power
When accelerating, Nissan's new hybrid uses both the gas engine and the electric motor, so both clutches are engaged. That's the first of the system's four operating modes.

In low-speed city driving — or in traffic jams and at stop signs — the electric motor can do all the work (it reportedly can move the car for up to 3 miles at city speeds before it needs help from the V6). As a result, the front clutch is disengaged because the engine is shut down.

At higher city and highway cruising speeds, the gas engine provides motivation and both clutches are engaged — the rear clutch channeling power from the spinning electric motor back into the battery pack to help replenish its juice.

And finally, when the car is braking, the gas engine and front clutch shut down, and the heat energy from braking the rear wheels generates electricity that is channeled through the rear clutch and into the battery pack.

Low Carbon, High Profit
Nissan is launching the hybrid as part of what it sees as a well-rounded portfolio of green technologies that will help it achieve a goal of reducing carbon dioxide emissions from its cars by 70 percent from levels set in 2000.

The only way to slash CO2 — a by-product of burning hydrocarbon fuels like gasoline and diesel — is to improve mileage, and Nissan plans to use hybrids, battery and hydrogen fuel-cell electric vehicles, electricity and other fuels from renewable energy sources, improved gasoline engine technologies, more efficient transmissions and a host of other incremental improvements to achieve its goal by 2050.

Yet as Senior Vice President of Technical Development Minoru Shinohara emphasizes, Nissan wants to make sure that in striving to remove the negatives from the automobile, it doesn't shed the positive attributes of performance, enjoyment and utility in the process.

The presence of this new rear-wheel-drive hybrid system in this 2008 Infiniti G35 Hybrid Prototype is part of this effort. After all, Nissan's CEO Carlos Ghosn has mandated that every car, no matter how green, must bring in the green as well. And a luxury rear-wheel-drive hybrid can attract deep-pocket buyers in a way that a Prius cannot.