What we mostly knew about the new Malibu hybrid when we drove it last year was that it had graduated from a mild belt-alternator-starter system to the big-boy Chevy Volt’s architecture. Now that the EPA numbers are official (47/46/46 city/highway/combined!) and cars are shipping to dealerships, Chevy sat us down to explain some interesting differences in the Malibu’s riff on the Volt’s electrical architecture.
Only an absolute expert will be able to distinguish between the electric transaxle drive units of a Volt and a Malibu, even in cutaway form, but five parts differ. The rotors on both electric motors and the stator for motor A are new, tailored to the Malibu’s different driving characteristics—namely, operating with the engine running most of the time. In the Volt, motor A manages to forego pricey rare earth magnets for cheaper ferrite ones, putting out 64 hp. This design is most efficient during charge-depleting (electric-only) driving. In the Malibu, neodymium-iron-boron magnets are used, boosting output to 74 hp and delivering lower losses during the charge-depleting mode, which the Malibu spends most of its time in. Motor B employs rare earth magnets in both cars, but in the Malibu the output drops from the Volt’s 117 to 102 hp—a change that didn’t require a new stator.
Since the Volt must be able to deliver peak acceleration with the engine off, there is a one-way clutch that prevents the engine-input shaft from rotating during hard acceleration. The Malibu doesn’t need that part, because it never accelerates hard without the engine. Leaving it in caused parasitic losses, so it’s out, partially defraying the increased cost of the fancier magnets. Finally, the Malibu’s 306cc larger 1.8-liter engine required stiffer springs on the input shaft torsion damper. Beyond that, there are some calibration tweaks and a slightly different connector shield (required for the different crash characteristics).
Speaking of that “Midsize Gasoline Engine Family” 1.8-liter, it gets a few spiffs unique to its new hybrid role, including pistons and rods that provide 11.5:1 compression, a single-volume close-coupled catalyst, and a direct-to-the-block mount for the A/C compressor. The bigger changes are a cooled exhaust gas recirculation system to optimize fuel economy (all the cool new hybrids are getting this feature) and an exhaust-heat recovery system. During cold starts this feature temporarily diverts hot exhaust gasses exiting the catalyst through a heat exchanger to warm the engine coolant much more rapidly. This improves both emissions light off and the time required to warm the cabin. It also lets the powertrain function with the engine off for 50 percent or more of the time on the fuel-economy test schedule, even when run in 20-degree weather.
The meticulous calibration of these two retuned motors and the Voltec’s double-planetary transaxle’s four operating modes allow the Malibu Hybrid to drive the city-oriented fuel-economy test schedule and the more highway-oriented US06 schedule with this highly efficient engine operating within 2 percent of its peak brake-specific fuel consumption for most of the time. That’s how Chevy manages to land those big EPA numbers.
Read our 2016 Chevrolet Malibu Hybrid Quick Test Review RIGHT HERE
Voltec 3.0?
Almost no details are available yet, but Chevy’s Voltec folks let slip that the forthcoming Cadillac CT6 hybrid’s Global Rear-drive Electric (GRE) powertrain will expand upon the Volt and Malibu Hybrid’s GFE (front-drive) architecture by adding a third planetary electric motor element.
Malibu Hybrid Battery Pack
The power-biased type of battery best suited to a charge-sustaining hybrid like the 2016 Malibu’s is necessarily very different from the energy-biased types used in pure EVs and range-extended EVs such as the Volt. This new pack marks a quantum improvement relative to the one in the 2008-2009 Malibu Hybrids, but the chemistry is the same: lithium-ion graphite mixture with a nickel-manganese cobalt-oxide cathode. This type provides the strong cold-cranking amps required to start the engine. Power density improves greatly by switching from cylindrical to flat pouch-type cells grouped 10 cells to a module, with eight modules comprising the pack. It stores 1.5 kW-hr, triple the old Malibu Hybrid pack’s energy with 75 percent greater power density. It’s air-cooled, drawing air from the passenger compartment, and the pack weighs just 95 pounds. Expect the forthcoming Silverado Hybrid (due in fall 2016) and the Cadillac CT6 Hybrid to employ their own unique battery packs using this same cell-and-module layout.
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