With all the recent buzz and federal dollars going to all-electric cars, the opposite—and more practical and affordable—end of the gas-electric spectrum is missing in action in the United States. Micro-hybrids, also known as start-stop systems, use regenerative braking and battery storage to allow cars not to burn fuel while at a stop. Cars using stop-start do not provide propulsion to the wheels, but the technology is low hanging fruit—a cheap and easy way to get about 10 percent more miles per gallon. The cost of a micro-hybrid system can be as low as $500 per vehicle.
Automotive News reported this week that Mazda is struggling to bring micro-hybrids to the US. The company says its system, called i-stop, is good for a 10 percent fuel economy improvement in big city driving, but complained that the US Environmental Protection Agency does not account for the system’s benefits in emissions and mileage testing. Could America’s environmental agency be the stumbling block to bringing a technology to market that some observers think should be required as standard equipment?
Europe sees micro-hybrids as a key strategy for reaching stricter emission standards. Industry analysts forecast that micro-hybrids will exceed all other forms of gas-electric technology. More than 1 million vehicles could use micro-hybrid technology in 2010. Strategy Analytics Automotive Electronics Service forecasts that global sales of stop-start micro-hybrid systems will reach nearly 20 million units a year by 2015. Auto supplier Bosch has sold more than a half-million stop-start systems to BMW, which offers the system as standard equipment in its 1-series vehicles. Supplier Valeo—which estimates that in cities, cars spend up to one-third of their time idling at a standstill—announced last year that it agreed to supply 1 million systems to PSA Peugeot-Citroën by 2011.
A micro-hybrid is the simplest kind of gas-electric technology. It is commonly composed of an energy storage device—like a battery—and a beefed-up starter-motor that can also act as a generator. The car’s engine control unit shuts off the engine when the car slows down or comes to a stop. As soon as the driver puts in the clutch, moves the shift lever, or accelerates, the battery powers the starter motor, which quickly switches on the engine. Stopping the engine while vehicle is at idle conserves fuel, but one disadvantage to this type of system can be the noticeable starting and stopping of the engine.
Mazda’s ”i-stop” uses a different approach, restarting the engine through combustion. Mazda’s system initiates engine restart by injecting fuel directly into a cylinder while the engine is stopped, and igniting it to generate downward piston force.
The upcoming 2009 Frankfurt Auto Show will debut the BMW 320d diesel vehicle and Kia Venga, which will both use stop-start. Europe has so many cars with stop-start that the UK’s AutoExpress recently did a “shoot out” comparing the systems. The BMW 320d beat out its competition—including the Volkswagen Passat BlueMotion diesel, Toyota Auris (sold as a Corolla hatchback elsewhere), Mini Cooper, Citroen C2, and Smart ForTwo.
AutoExpress described the BMW 320d’s stop-start performance: “When you come to a halt at a red traffic light, select neutral and take your foot off the clutch. The power is cut quietly, and you’re left to wait in vibration-free silence.”
In the US, it’s the automakers that are silent. General Motors flirted with micro-hybrid technology in its first hybrid pickups, as well as the early version of its Saturn hybrids. But with the discontinuation of the company’s mild hybrids, the US market is lacking a single micro-hybrid.