The 2013 Cadillac ATS made its world debut Jan. 8 at the 2012 North American International Auto Show in Detroit with an all-new turbocharged direct-injected 2.0-L inline four among the compact sport sedan's three engine choices.
"This engine was designed specifically for the ATS, and that will be its first application," Dave Leone, General Motors Global Vehicle Line Executive for RWD and Performance Cars, told AEI. "There will be other applications to follow."
The 2012 Buick Regal GS and Regal Turbo sedans use a turbocharged 2.0-L Ecotec producing an SAE-certified 270 hp (201 kW). The new 2.0-L destined for the Cadillac, though not officially certified as this article went to press, is estimated to achieve the same peak rated power and the same specific output: 135 hp/L (101 kW/L). It delivers 90% of its estimated peak 260 lb·ft (353 N·m) from 1500 to 5800 rpm.
Compared with the engine used in the Buicks, the new 2.0-L features a new cylinder block and head, and new balance shafts, crankshaft, valves, and induction system.
"It's not a slightly modified version of today's engine," Leone said. "Compared to today's engine, more than 95% is new hardware."
AEI interviewed the engine's Chief Engineer, Mike Anderson, during a December media briefing at General Motors' Warren, MI, design center.
Q: Engine friction is reduced approximately 16% compared to the current engine. How was that accomplished?
A: The team worked to reduce the friction of every part that rotates, reciprocates, or otherwise mechanically interacts with another part. But we also added new technologies, like an electronically controlled variable-displacement oil pump, which is located at the back of the balance shaft module. It's not GM's first variable-displacement oil pump, but it's the first one that's actively controlled by the engine's computer. This level of control allowed us to run less oil pressure over a very large range of engine operating conditions.
Less pressure means less fuel used to run the pump as well as lower mechanical forces inside the pump, which translates to less noise at the driver's ear.
Q: Why a new combustion system?
A: The capability of GM's proprietary design and analysis techniques using computational fluid dynamics have grown to the point that we were able to explore the combustion system design space more comprehensively than ever before. Key combustion system parameters such as injector spray pattern, piston topology, intake and exhaust port geometry, and installation angles of the valves and injectors have all been optimized to achieve a great balance between in-cylinder mixture motion and flow. For the customer, this means more efficiency at segment-leading levels of power density.
Q: What makes this engine even quieter than the current engine?
A: We worked to reduce or contain all sources of noise and improve the tonal frequency of the sounds that remained. For instance, we moved the balance shafts from the block into a precision gear-driven module that is 'buried' in the crankcase. In addition, we moved from roller chains to inverted-tooth chains to drive the balance shaft module and the valvetrain. An inverted-tooth chain more smoothly engages and disengages the drive sprockets and behaves like a 'silent' chain.
Also, as aluminum is a natural 'speaker' for engine noise, we used finite element analysis on several components, including the cam cover and front cover, to push their radiated sounds into a higher frequency range—well above 2000 hertz—which is more pleasing to the ear. We also increased the number of fasteners on these covers to further increase stiffness and improve refinement.
The Cadillac ATS's base engine will be an all-new 2.5-L I4, details of which will be forthcoming. The ATS also will offer the 3.6-L V6 currently used in the Cadillac CTS and SRX.