The Cadillac CT6 Hybrid powertrain was the subject of a technical overview at the recent SAE 2016 Hybrid and Electric Vehicle Technologies Symposium in Anaheim, California. The presentation was led by Tim Grewe, general director of electrification and Pete Savagian, general director of electric drives and systems engineering reports Green Car Congress.
The CT6 hybrid powertrain has a total of 449 horsepower, 266 from a turbocharged 2.0 liter 4 cylinder direct injection engine and 183 from a special transmission that houses dual electric motors. A liquid cooled 18.4 kWh battery allows for 37 miles of all electric range at speeds up to 78 mph. The car accelerates to 60 mph in 5.6 seconds. What is truly astonishing about Cadillac’s new large sedan is that, when equipped with this plug-in hybrid powertrain, it consumes less than 2 liters of fuel every 100 kilometers. That translates to 117.7 mpg in the US test cycle. Amazing.
“We have a PHEV system that has incredible efficiency, but it is also one of the highest performing vehicles on the road with extraordinarily connected feel to it,” says Tim Grewe.
The new electrically variable rear wheel drive transmission has 2 electric motors, 3 planetary gears, and 5 clutches that deliver four continuously variable transmission modes with 3 fixed gears. Providing all-electric launch, selectable regeneration, and power blending with the turbocharged engine, the transmission provides smooth and seamless power through the entire driving range. The system also includes an electric oil pump for the engine.
The first motor in the new system is an induction motor, which lowers production costs. It also does not use an rare earth materials. “The induction motor is something we are particularly proud of,” Grewe says. “We’ve done a great deal of work on interior permanent magnet machines, but we haven’t designed many induction machines.”
The second motor is a permanent magnet design. It is produced at the GM’s Baltimore facility, which also makes the motor for the Chevy Spark EV. The Cadillac unit is 50 mm shorter, however, which helps it fit within the casing for the transmission.
The battery for the CT6 is related to the one in the Chevy Volt but is packaged differently. In the Cadillac, the battery packs are mounted on their sides for more interior room. “[B]asically we cut out the whole back off the CT6, says Grewe. “We use the tray of the battery pack as the main floor structure. With the ability to handle the weight of the battery in the car structure, it really improved the stiffness. To handle that mass on the rear wheel drive, it actually made driveability better, because it is stiffer and engineered to go together.”
To make the car more fun to drive, GM added a third planetary gearset and two more clutches, Grewe says. “Basically, that gives you a Volt on steroids. It gives you tremendous launch torque. You look at some of the EV effort we have here, you’re almost above 5,000 newton-meters of torque. You have that EV launch feel.” Indeed, the larger, heavier CT6 is almost 2 seconds quicker to 60 than the Volt.
All CT6 Hybrids will be assembled in China. Any offered for sale in the US will be imported, rather than built domestically. That’s assuming any American buyers want a large, comfortable sedan that gets outstanding gas mileage. With gas selling for less than CocaCola, does anyone really car?
Photo credits: Green Car Reports