DETROIT – The 2013 Chevrolet Malibu Eco with eAssist technology is the most fuel-efficient Malibu ever – delivering a GM-estimated 37 mpg on the highway, thanks to smart electric technology that doesn’t affect ride or performance.
The 2013 Malibu Eco is the first Chevrolet vehicle to feature eAssist. Along with specific aerodynamic enhancements, it achieves 12-percent greater highway fuel economy than current models equipped with the 2.4L engine.
“Malibu Eco’s eAssist system integrates regenerative braking with the latest lithium-ion battery technology, to give our customers significant fuel-efficiency gains,” said Steve Poulos, global chief engineer of eAssist.
“Providing electric boost to the powertrain system during heavy acceleration and grade driving helps the transmission operate more efficiently. The engine’s start-stop and fuel shut-off during deceleration features add to the fuel savings.”
The eAssist system is made up of a 32-cell, 0.5-kW lithium-ion battery, an electric motor-generator and next-generation six-speed transmission. The system’s electric motor-generator is mounted to an Ecotec 2.4L four-cylinder engine, in place of the alternator, to provide both motor assist and electric-generating functions through a revised engine belt-drive system. The motor-generator is a high-performance, compact induction motor that is liquid-cooled for increased performance and efficiency.
The air-cooled 115V lithium-ion battery is integrated into a power pack located in a compartment between the rear seat and trunk. The power pack is surprisingly compact and lightweight, weighing only about 65 pounds (29 kg). It allows rear access to the trunk via the split-folding rear seat, unlike other hybrid competitors.
Trunk space is slightly reduced from 2011 models, but still offers 14.3 cubic feet (405 liters) of storage for luggage, golf clubs and other large items. An electric fan cools the power pack, drawing air from a vent located in the package tray, behind the rear seat.
The induction motor-generator bolsters the engine with approximately 11 kW (15 horsepower) of electric power assist during heavy acceleration and 15 kW of regenerative braking power. This power capability enables the battery to capture energy during regenerative braking for improved fuel economy.
e Assist technology also allows for a numerically lower 2.64 final drive ratio. As a result, the Malibu Eco can travel 580 highway miles (965 km) between fill-ups, despite having a smaller (15.8-gallon / 59.9 L) fuel tank than other 2013 Malibu models (18.6-gallon / 70.4 L).
The system also enables the Ecotec engine to shut down fuel delivery in certain deceleration conditions, which saves fuel. While in fuel shut-off mode, the motor-generator unit continues spinning along with the engine to capture regenerative braking power and provide immediate and smooth take-off power when the driver presses on the accelerator.
Then, as the vehicle comes to a stop, the motor-generator unit spins the engine, bringing it to a smooth stop – and properly positions it for a smooth and seamless restart.
“The battery system is designed to provide power assistance to the internal combustion engine, rather than storing energy for all-electric propulsion,” said Poulos. “It’s really an extension of the conventional internal combustion engine, not a replacement for it.”
Additional fuel-saving features include:
An aerodynamically optimized exterior, including underbody panels and electronically controlled shutters in the lower grille that close at higher speeds to push more air over and around the vehicle.
Lightweight components and systems, including an aluminum hood, aluminum rear bumper beam, low-mass carpet and dash mat and more, save approximately 130 pounds (58 kg) compared to comparably equipped non-Eco models.
An Eco gauge in the cluster continuously responds to driving behavior, encouraging fuel-efficient driving, while an Auto Stop Indicator on the tachometer informs the driver when the engine is in start-stop mode.
A power flow display in the driver information center – or the center console screen when equipped with the navigation system – indicates which of the following modes the Malibu Eco is operating in:
Battery charging – the eAssist motor is charging the high-voltage battery when the vehicle is slowing.
Electric assist – the eAssist motor is providing electric power boost to the engine
Auto-Stop – the vehicle is stopped, the engine has automatically shut off and is ready to automatically restart when needed.
Driver-selectable modes are offered to enable maximum comfort or efficiency of the air conditioning system and include:
Eco mode – which maximizes the frequency and duration of Auto-Stop, while providing excellent cabin comfort
Comfort mode – reduces the frequency and duration of Auto-Stop to maximize cabin comfort.
2.4L Ecotec engine and next-generation six-speed
The eAssist system works with Malibu’s 2.4L Ecotec four-cylinder engine, which features fuel-saving variable valve timing and direct injection technology. It is rated at 182 horsepower (136 kW) and 170 lb.-ft or torque. That’s 13 more horsepower and 12 more lb.-ft of torque than the previous Malibu. – and it’s more power and torque than the 2012 Toyota Camry Hybrid, 2012 Hyundai Sonata Hybrid, and 2012 Ford Fusion Hybrid.
The next-generation Hydra-Matic 6T40 six-speed transmission is designed to enhance powertrain efficiency.
Significant internal transmission changes to clutch controls and hardware provide reduced spin losses while improving shift response and time. The added electric power provided by the eAssist system allows for higher gearing to improve steady state efficiency without impacting acceleration performance or driveability.
The system’s ability to provide some electric assistance at cruising speeds allows the driver to accelerate lightly or ascend mild grades without the transmission downshifting. Automatic Grade Braking keeps the transmission in a lower gear when decelerating or coasting on a downgrade, helping to improve brake wear performance.
An auxiliary, electric-driven transmission oil pump is added to the 6T40, which keeps the transmission primed and the fluid flowing when the engine shuts down at a stop. That keeps the transmission ready to perform when the driver accelerates, for a seamless, uncompromised driving experience.
“It’s a very integrated powertrain system, with no compromises in driving performance, shift quality or ride and handling,” said Todd Stone, Malibu lead development engineer. “We believe this combination points to the future of vehicles powered primarily by an internal combustion engine.”
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