'Cadillac Of Powertrains' Drives The New CTS
FOR RELEASE: August 16, 2001'Cadillac Of Powertrains' Drives The New CTS
Nürburg, Germany. - In creating the new Cadillac CTS sports sedan, General Motors engineers benchmarked the competition's best, including the BMW 528i sedan. The CTS is designed to bring a performance quotient and a fun-to-drive factor to match its eye-catching exterior design.
Designed from the ground up with an exclusive rear-wheel-drive architecture, the new CTS can accelerate from 0-60 mph in less than seven seconds when equipped with the manual transmission. This is complimented with excellent road handling capabilities unlike any Cadillac ever produced. Also, like any true sports sedan, the CTS has something no rear-wheel-drive Cadillac has had in 50 years: a manual transmission. Combined with rear-wheel drive and a 220-hp 3.2-liter V6, the setup will leave very little doubt that Cadillac is poised to reclaim world leadership in affordable luxury accompanied by bold, striking design and exhilarating, outstanding performance.
The Science behind the Art: New 3.2-liter DOHC V6 The 3.2-liter V6 powering the CTS in North America has been fully revised to improve driveability, power, torque and emissions. It's designed to take full advantage of every bit of its 220 horsepower, with the induction and exhaust system allowing the engine to breathe freely and easily. The Engine Control Module (ECM) is calibrated for maximum power when it's needed most.
While most V6 engines use a 60-degree inclination, the CTS Team chose the 54-degree bank angle because of the wide cylinder head assembly inherent to the double-overhead camshaft layout. The reduced bank angle was chosen to accommodate the packaging requirements of the CTS.
Although the cast-iron cylinder block may appear the same externally as the previous engine, the 3.2-liter 54-degree V6 is actually an all-new design. The 54-degree angle between the cylinder banks is unique among General Motors four-camshaft V6s. This compact packaging makes it appropriate for both transverse and longitudinal applications.
Martin Vögler, GM Europe engineer in charge of the 54-degree project, said, "We needed to pick up what we would lose due to the different exhaust after-treatment system, as well as to improve the launch performance of the car, providing more low-end torque, and therefore flexibility."
The longitudinally mounted V6 features a stiffer, stronger cylinder block, forged steel crankshaft, improved lubrication, better cooling, higher fuel pressure delivery to improved fuel injectors, an improved combustion chamber design to reduce unburned hydrocarbons and a drive-by-wire throttle system for better emissions performance. Improved breathing is through a redesigned intake manifold and sheetmetal exhaust manifolds.
For export markets in Japan and Europe, the CTS will also be available with a 2.6-liter V6, essentially an enlarged version of the 2.5-liter V6 offered in Europe. Maximum power of both engines occurs at 6000 rpm, with the 3.2-liter making 220 hp against 200 hp at 6,000 rpm for the previous 3.0-liter. The 2.6 produces 175 hp versus 168 hp at 5800 rpm for the previous 2.5 liter in Europe.
Maximum torque occurs at 3400 rpm for both engines, with the 3.2 providing 218 ft.-lbs. and the 2.6 yielding 171 ft.-lbs.. The latest version of the 54-degree V6 meets US Federal LEV emission requirements, as well as Euro 3 levels in its European form.
Two new transmission choices
For the first time in approximately 20 years, a Cadillac will be available with a manual transmission, which, along with the rear-drive application, underscores GM's flagship division's commitment to making the CTS a true driver's car.
The five-speed manual from Getrag, also found in the Holden Commodore, uses a rod-actuated shift linkage and is characterized by its durability, smoothness and accurate shift feel. Once the Getrag unit was decided upon, the CTS team began adapting it for service and to meet the quiet operation required in a Cadillac.
Changes included:
- Larger diameter drive axles
- Foam-filled, two-part driveshaft
- Soft rubber coupling design for the driveshaft
- Reprogrammed ECM to anticipate gear changes and reduce torque
- Revised transmission mount at the rear for better isolation
- Addition of rubber shifter bushing for increased noise isolation
- Increased acoustic baffling and foam in the transmission tunnel
- Dual-mass flywheel to isolate engine torque pulses and smooth neutral gear rattle
The clutch actuation is performed by a concentric hydraulic slave cylinder. The concentric cylinder applies clutch load more evenly and provides a more linear load and a more progressive feel. A self-adjusting clutch was selected to provide consistent pedal effort over the life of the vehicle.
Customers not selecting the manual will receive a GM first: a five-speed electronically controlled automatic transmission, the 5L40-E Hydra-Matic. This GM-designed transmission also is used in the BMW 5 Series and X5 SUV.
A state-of-the-art transmission, the light and compact 5L40-E features a full complement of advanced electronic control capabilities. These include a shift mode button that allows the driver to select between "Sport," "Winter" and "Economy" modes, shift patterns that adapt to driving conditions and driver style, traction control capability, engine torque management during shifts, and powertrain protection capabilities. Another electronic feature is also a first for GM: engine braking in all five gears, giving the automatic the same sporty feel as downshifting a manual.
The 5L40-E uses an electronic controlled capacity clutch in the torque converter, instead of a mechanical lock-up clutch. This clutch uses sophisticated electronics to maintain very small amounts of slip between the pressure plate and the torque converter housing cover, and to maintain a slight hydraulic cushion between the two halves of the torque converter. The ability to precisely control continuously variable amounts of slip leads to reduced torque pulses and allows the clutch to be applied at lower vehicle speeds and with smoother engagement. This results in improved driveability and better fuel economy.
The electronics that control the "Sport Shift" adaptive mode are highly advanced. Sport shift algorithms analyze throttle inputs, cornering factors (wheel speed differences from left to right), and vehicle speed. Based on these parameters, the 5L40-E is able to identify high-performance inputs from the driver and hold a gear after the driver's foot is lifted off the accelerator pedal. Sensing cornering factors above a certain level, the 5L40-E will hold the gear indefinitely.
Both CTS transmissions, mated to the 3.2-liter DOHC V6 and transferring its power to the car's rear wheels, help carry out the vehicle's mission to be a world-class sports sedan.