Getting a charge out of Nissan’s Leaf
This thought came to me as I was piloting the Nissan Leaf electric vehicle prototype around Dodger Stadium last Friday: When gasoline-powered cars sleep at night, they dream of being electric.
Think about it: Every year, automotive engineers find new ways to smooth more rough edges off the conventional automobile. For example, long gone are the rude jolts that used to accompany gear changes in automatic transmissions. These have been ironed out either by continuously variable transmissions (which have no stepped gear intervals) or by sophisticated suites of computer programming that modulate engine torque at the precise moments of gear change. Even set-to-kill sports cars like Ferraris and Lamborghinis and Porsches -- cars that used to wrench your neck like a Leavenworth hanging -- now shift gears with a kind of eerie, liquid transparency. The only things that change are engine pitch and the needle on the tachometer.
This level of refinement, which is such a struggle to achieve in conventional cars, is a birthright of electric cars. In the Leaf -- an all-electric, five-passenger car that will start hitting American streets in late 2010 -- you step on the accelerator and the car spools out velocity in one continuous, syrupy stream. It’s nothing short of elegant.
Once upon a time -- 10 years ago -- cars had such things as torque curves. Which is to say that, because of the peculiarities (the volumetric efficiency) associated with different internal combustion engine designs, each model of car hit maximum torque at a particular rpm. Cars with big American push-rod V8s under the hood typically had massive torque at lower rpm, and cars with multivalve overhead-cam fours and sixes hit peak torque at higher rpm.
These liabilities have been largely erased in the current generation of cars, thanks to computer-controlled throttles, variable valve timing and duration, forced induction and variable-geometry intake manifolds -- all of which help optimize the flow of gas in and out of an engine and establish a “flat” torque curve. In the case of a BMW twin-turbo 3.0-liter engine, for example, maximum torque comes at 1,400 rpm and doesn’t start to go away until 5,000 rpm.
The BMW engine is, in other words, more like an electric motor. In fact, an EV’s motor produces maximum torque at 0 rpm and maintains consistent torque across most of its operating speed range. That’s what makes EVs such little hot rods -- loads of off-the-line quickness and mid-range punch.
During my all-too-brief drive, the Leaf prototype (clad in Nissan Versa bodywork), with three people on board, shot across the stadium parking lot like it had been pinged with a BB gun. Zero-to-40 mph acceleration, I estimate, is in the mid-5-second range, which would suit a decently sporty little car. Arrayed around the Leaf chassis is 90 kilowatts worth of lithium-ion batteries driving an electric motor good for 106 horsepower and a healthy 207 pound-feet of torque. According to Nissan, the Leaf’s top speed is 90 mph and the nominal range is 100 miles.
One last tech-wonk example: Automakers are continuously evolving technology to help cars maintain traction and directional stability. With conventional traction and stability systems, if wheel slip or vehicle yaw is detected, the computers will pulse the appropriate wheel’s brake or retard engine timing or both, until the vehicle regains stability. But this is a big, sloppy, coarse means of doing the job. What’s needed is a finer-grain method of modulating wheel speed without scrubbing off all the speed and momentum.
Electric motors are instantly and almost infinitely variable, and are vastly more articulate with regard to changes in traction. This is why the Tesla Roadster, which can maintain almost 100% traction at the rear wheels under acceleration, corners harder and faster than the Lotus Elise upon which it is based.
Imagine the potential road-holding power of an all-wheel-drive electric sports car, such as Audi’s promised e-Tron. Imagine what you could climb with an electric Jeep.
Here’s my point: As repeatedly underlined at the Nissan Leaf’s U.S. debut last week, the future of EVs comes down to the question of consumer acceptance. Will consumers buy them? Will they like them? What about battery leasing and recharging infrastructure, and carbon emissions? What about cost? These are reasonable questions.
But I predict consumer acceptance will ultimately be a nonissue. Why? Because the trajectory of vehicle engineering has trained car buyers to expect their next car to be smoother, quieter, quicker, more high-tech, with better cabin isolation and more road-holding, than the one before.
Two decades of computerization of the automobile have created a kind of well-oiled semiautonomous being, half semiconductor, half metal and glass. Many cars today have electric steering, electric brakes, virtual gauges, video camera mirrors, even virtual bumpers. In other words, cars are nearly electrified already.
The next logical -- even inevitable -- step in the evolution of the automobile is when we jettison the big, heavy, hammering, noisy piece of reciprocation under the hood.
The Leaf is definitely Car 2.0. Sweet, glycerin smooth, techy, frisky and even a little bit beautiful. It just feels like tomorrow. Perhaps the question is not “Will people buy them?” but “Can we build enough?”