POWERTRAIN: STS DELIVERS REFINED POWER, TORQUE

[Bruce Nunnally]

Rear- or All-Wheel Drive Performance

255-hp 3.6L V6 VVT Engine

320-hp 4.6L V8 VVT Northstar Engine

Electronically Controlled Transmissions with Driver Shift Control

With delivery to showrooms scheduled for the fourth quarter of 2004, the all-new 2005 STS will be Cadillac’s first rear-wheel-drive entry in the luxury performance sedan segment in more than 25 years, and its first-ever all-wheel-drive sedan offering.

The STS will be equipped with two engine offerings, including a 320-horsepower 4.6-liter Northstar V-8 with 315 lb-ft of torque, or 3.6-liter 255-horsepower V-6 with 252 lb-ft of torque (estimated). The STS also will be available with all-wheel-drive (AWD) on vehicles equipped with the Northstar V-8.

The 4.6-liter Northstar is expected to deliver 0 to 60 performance at or less than 6.0 seconds. With the V-6 or AWD V-8, the STS is targeted to achieve 0 to 60 performance in under 7.0 seconds.

The V-6 and V-8 are mated to electronically controlled five-speed automatic transmissions – the Hydra-Matic 5L40-E is mated with the V-6, and the Hydra-Matic 5L50-E is mated with the V-8 and has both rear- and all-wheel-drive applications. The 5L50-E is designed to handle the V8’s torque, with a 25 percent torque capacity increase over that of the 5L40-E.

3.6-liter V-6 VVT engine

The 60-degree 3.6-liter V-6 is a highly refined, DOHC four-valves-per-cylinder engine with all-aluminum construction. The valve train configuration includes roller finger followers.

The adoption of fully variable valve timing for both intake and exhaust valves provides outstanding flexibility, fuel economy and emissions reduction. The four-cam variable valve timing is a key element in the V-6’s control strategy, which gives the engine a wide-ranging flexibility. For example, 90 percent of the 3.6L V-6’s peak torque is available across a remarkably broad operating range: from 1,600 rpm to 5,800 rpm. In addition, an electronically controlled throttle (ETC) effectively coordinates the driver’s intentions with the actions of the various control components.

Numerous design features were incorporated into the 3.6-liter engine to ensure it is one of the most advanced V-6 offerings in the world. These include:

A dual-stage variable intake manifold (VIM). The VIM incorporates a switch in the manifold that automatically changes the plenum volume available for resonance tuning of the inlet flow path.

Micro-hybrid engine control unit (ECU). The V-6’s ECU represents the latest in engine-management hardware, as well as the software that dictates every aspect of engine operation.

Specially isolated cam covers incorporate an isolated gasket around the cover perimeter and radial lip seals at the tubes through which each spark is inserted.

Three pressure-actuated piston-cooling oil-jet assemblies in the block each hold a pair of oil squirters that douse the underside of the piston and the surrounding cylinder wall with cooling oil. The benefit is piston temperatures resulting in more engine power.

Polymer coating on the piston skirts helps the piston to track more smoothly and quietly in the bore.

A new oil pump design, the product of a highly specialized analysis of pump flow, prevents noise caused by oil aeration.

A forged steel crankshaft delivers additional stiffness for better noise, vibration and harshness performance; ensures the durability required of high specific output variants; and provides an extra degree of robustness.

Northstar V-8 engine

The 4.6-liter Northstar V-8 is a 90-degree DOHC four-valve-per-cylinder engine, with an aluminum block and cylinder heads and valve train with roller finger followers. The Northstar is equipped with a host of technologies, including:

Four-cam continuously variable valve timing (VVT) for improved performance, refinement, economy and emissions.

Electronic throttle control, providing additional driving refinement. This allows the engine control system to precisely and seamlessly tailor vehicle performance to the driver demands.

Low restriction intake and exhaust manifolds and cylinder head ports designed to ensure optimum airflow and cylinder-to-cylinder distribution for maximum performance and emissions control.

Close coupled catalytic converters, mounted directly adjacent to the exhaust manifolds. They reach effective operating temperature more rapidly after engine start.

New air induction system, redesigned for enhanced capacity and noise attenuation. It features tuned resonators, additional resonators in the clean air duct and use of isolator pads in the clean air duct mounting.

Powerful engine control module (ECM) and high-speed communication system dedicated to engine control. An extremely powerful, state-of-the-art ECM, with a 16-bit, 24 MHz dual microprocessor, high memory capacity, and a redundant “safety” processor backing up the ETC enables the Northstar engine to provide its advanced capabilities. A transmission control module (TCM) controls the transmission with inputs from the ECM.

Polymer-coated pistons and cast-iron exhaust manifolds to further reduce noise, vibration and harshness.

A forged steel crankshaft delivers additional stiffness for better noise, vibration and harshness performance; ensures the durability required of high specific output variants; and provides an extra degree of robustness.

Rear wheel drive

Rear-wheel-drive STS offerings (V-8 and V-6) offer an available limited slip differential, which mechanically limits wheel spin on all surfaces for improved vehicle performance during handling maneuvers.

Vehicles equipped with the V-6, which are only available in rear-wheel-drive, have a performance-optimized drive ratio of 3.42.

Vehicles equipped with the V-8 engine are available with three final drive ratios configurations; 2.73 for enhanced fuel economy; 3.23 for mid-sport performance; and a 3.42 for optimized performance. Exported vehicles are only equipped with the 3.42 final drive.

All wheel drive

Vehicles equipped with all wheel drive (V-8-equipped vehicles only) have a final drive ratio of 3.23. The system incorporates a 40/60 rear bias torque split to provide the STS with superior handling performance, acceleration, traction, and control for dry, wet, icy, and snowy road conditions. Its three open differential layout, coupled with four-wheel traction control, balances driving torque distribution to each wheel and minimizes wheel spin to optimize on-road performance.

Electronically controlled transmissions

The V-8 and V-6 are mated to electronically controlled five-speed automatic transmissions – the Hydra-Matic 5L50-E is mated with the V-8, and the Hydra-Matic 5L40-E with the V-6. Both transmissions incorporate Driver Shift Control (DSC) and Performance Algorithm Liftfoot (PAL) technologies.

Driver Shift Control enables the driver to switch from automatic to a clutchless five-speed high-performance manual transmission. Once the driver moves the gearshift lever into DSC mode, a quick tap is all that is required for smooth, crisp upshifts or downshifts within a selected range.

Performance Algorithm Liftfoot inhibits upshifts while maintaining engine braking following continuous performance driving. The transmission control module (TCM) monitors driver behavior to determine whether or not to enable this feature. For example, if the system detects a drop in vehicle speed prior to entering a turn or a lane change, up to two downshifts can occur to provide the driver with maximum vehicle performance.

[Bentham]

Driver Shift Control enables the driver to switch from automatic to a clutchless five-speed high-performance manual transmission. Once the driver moves the gearshift lever into DSC mode, a quick tap is all that is required for smooth, crisp upshifts or downshifts within a selected range.

Ahh.. that answers that question

-Eric