Tech tweaks cut fuel use in new cars
Fewer fill-ups, reduced emissions an ongoing mission
In this second week of entries for the 2012 edition of the Automobile Journalists Association of Canada Technology Award are new powertrain answers to the auto industry’s ongoing quest for improved fuel economy and reduced auto emissions.
The winner of this award will be announced at the opening of the Canadian International Auto Show in Toronto next month. What follows is a short overview of three entries (the remaining entries will be covered in next week’s Auto View column).
GM eassist
Available in special edition versions of Buick’s La Crosse and Regal models and the upcoming 2013 Chevrolet Malibu, eassist is a relatively inexpensive, compact and lightweight mild hybrid powertrain system. Fuel savings can be up to 17 per cent on the highway and a whopping 23 per cent in the city.
The eassist’s compact 115-volt air-cooled lithium-ion battery pack only weighs 29 kilograms (65 pounds) and is positioned in a compartment between the rear seat and trunk. Electric fans draw air from the passenger cabin, from vents in the rear package tray, to cool this power pack. An integrated inverter also supplies 12-volt power.
The system’s motor-generator is externally mounted to a 2.4-litre Ecotec 4-cylinder gas engine and takes the place of a conventional alternator. Its motor assist and electric-generating functions are provided through a new-design engine belt-drive system.
The compact high-performance induction motor is liquid-cooled. It can provide the gas engine with 11 kilowatts (15 horsepower) of electric power assist during heavy acceleration and up to 15 kilowatts of regenerative braking power, which reduces brake pad wear.
The system also allows the Ecotec engine to shut down fuel delivery in certain deceleration conditions, to save additional fuel. While in fuel shut-off mode, the motor-generator unit continues spinning along with the engine to provide immediate and smooth takeoff power when the driver presses on the gas pedal.
GM’S Voltec Propulsion
Voltec Propulsion is the drive system that propels the Chevrolet Volt, which GM describes as an “extended range electric vehicle.” That’s because all of the Volt’s drive power is provided by an electric motor. However, unlike a pure electric car, it also has a small gas engine that generates electricity to recharge its battery and extend its driving range.
The Volt’s large battery pack is recharged by plugging the Volt into the main electrical grid. It takes about three to four hours, when connected to a level-2 (240 volt) charger. It’s a T-shaped 16-kwh lithium-ion battery pack that’s centrally located in the Volt and it supplies electrical energy to a 111-kw (149-hp) electric drive unit.
In pure electric-only mode, the Volt can provide a driving range of between 40 and 80 kilometres. If needed, the small 1.4-litre gas engine can extend its driving range by about another 500 kilometres. The Volt’s official government fuel consumption rating is 2.5 L/100 km (both city and highway), but actual consumption, if any, depends on the user. Mazda’s Skyactiv Technologies
Skyactiv is not a specific new technology from Mazda, but rather a collection of new technologies with a common goal — improved efficiency and fuel economy. Mazda claims that Skyactiv initiatives will cut fuel consumption by a whopping 30 per cent across the entire Mazda product line by 2015.
New engines with super-high compression ratios, new diesel engines with super-low compression ratios, plus the use of auto-stop and regenerative braking technologies are all part of the plan. So, too, are smaller, lighter transmissions and lighter vehicle bodies.
The 2.0-litre Skyactiv gasoline engine that will replace the current MZR 2.0-litre has a 13:1 compression ratio (production engines are generally no higher than 10:1), yet it runs on regular gasoline. At the heart of the engine is a uniquely designed smaller diameter piston with a central depression that’s used in a two-stage combustion process that provides a more complete burn.
This engine also uses continuously variable sequential valve timing (intake and exhaust) and internal friction has been reduced by 30 per cent. Mazda claims a 15-per-cent improvement in fuel economy and a 15 per cent boost in torque at low band mid range engine speeds, from an engine that’s 10-per-cent lighter.
Really good news is Mazda’s intention to offer the Skyactiv 2.2-litre diesel engine option in Canada. This engine’s very low (for a diesel) compression ratio of 14:1 is a world first for a production engine. Mazda also claims that it meets the highest environmental standards without the need for an exhaust after-treatment system.
Bob Mchugh is a freelance automotive journalist, writing on behalf of BCAA. Contact him at drivingwheel@shaw.ca