Post by Aurora40 on Dec 24, 2009 8:28:44 GMT -6
This is from GM's press release about the 2000 Cadillac Seville. However, the information is equally applicable to the 2001 Aurora V8 as it had the same redesign.
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Northstar System
In terms of performance, the Seville SLS and STS feature Cadillac’s widely praised Northstar dual overhead cam V8 engine with the enhanced StabiliTrak 2.0 stability control system, enhanced continuously variable road-sensing suspension, all-speed traction control, ABS and Magnasteer™ speed-sensitive steering.
The 2000 Seville benefits from the next step in modern engine design in the form of an improved Northstar V8. While the basic engine architecture remains a predominantly aluminum 4.6-liter DOHC 32-valve V8, major design improvements have been incorporated to deliver lower emissions, excellent mileage with regular fuel, and smoother, quieter operation.
The list of new Northstar V8 features includes:
* Roller-follower valvetrain design
* Improved combustion chamber configuration
* Center-feed intake manifold
* New pistons
* Coil-on-plug cassette ignition system
* Siemens powertrain control module (engine/transmission control computer)
* Exhaust manifolds with integral air-injection passages
* Flex pipe between the exhaust Y-pipe and the catalytic converter
* Twin electrically driven, two-stage air pumps (LEV applications only)
* Direct mounting of all engine-driven accessories (power steering pump, AC compressor, electrical generator)
* Integrated coolant crossover and throttle-body support
The Seville’s fuel recommendation changes from premium (93 octane, lead-free) to regular, resulting in a major reduction in operating expense. To facilitate this gain, the Northstar’s compression ratio was lowered from 10.3:1 to 10.0:1.
One result of these improvements is that the 2000 Seville will be certified for sale in California and certain Northeast states as a low emissions vehicle (LEV). This was achieved by means of a reaction-heated catalyst, pistons with reduced crevice volume and a new combustion chamber design.
Engine Design Changes
Revised combustion chambers are superior to previous designs in terms of both tumble motion of the incoming fuel-air mixture and burn rate. The intake and exhaust valves have been resized. Larger intake valves improve the engine’s breathing ability, while smaller exhaust valves increase flow velocity, an aid to catalyst light off.
While the new combustion chamber design helps maximize fuel efficiency, even larger gains are made by the addition of roller-follower devices between each cam lobe and valve stem. Compared to the previous Northstar’s direct valve actuation, the result is a substantial reduction in friction. During moderate driving conditions, the torque necessary to turn Northstar’s four camshafts is reduced by 50 percent or more.
The Northstar also benefits from a new ignition system that delivers power to the spark plugs directly instead of through wiring. A cassette containing four ignition coils linked by short secondary leads to adjoining spark plugs now attaches atop each cylinder head cover.
In addition to improved reliability, the new ignition system permits scheduling the magnitude of the voltage sent to the spark plugs. High voltage is used during full-load, high rpm and heavy EGR (exhaust gas recirculation) conditions to guarantee complete combustion. The energy level is reduced to minimize electrical loads and radio frequency interference during light-load conditions, such as medium speed cruising. The result is extended spark-plug life and a peak energy capacity that is 130 percent higher than the system it replaced.
Northstar’s new powertrain control module is a single circuit board device housed within a sealed aluminum case engineered to withstand the harsh underhood environment. The module contains dual microprocessors to monitor and direct engine and transmission operations.
Noise and vibration improvements are the result of adopting a center-feed design for the composite-plastic intake manifold, as opposed to the previous end-feed design. The new design facilitates a near equal-length induction path for all eight cylinders. In contrast, the previous design provided a long path to the front cylinders and shorter paths to rearward cylinders. With the reduction or elimination of many harmonic tones, the resulting induction sound is more of a hum.
A molded-plastic cover backed with acoustical foam rests above the intake manifold to reduce induction, fuel-injector and other noises radiated by the engine. Direct mounting of accessories eliminates flex and vibration inherent with extra brackets. A flexible connection in the exhaust system en route to the catalyst helps quell another source of noise and harshness.
Outstanding Power, Torque
The 4.6-liter dual-overhead-camshaft Northstar V8 installed in the SLS generates 275 horsepower (205 kW) at 5600 rpm and 300 lb.-ft. (407 N•m) of torque at 4000 rpm. The sportier STS is equipped with a retuned version of the Northstar V8 producing 300 horsepower (224 kW) at 6000 rpm and 295 lb.-ft. (400 N•m) of torque at 4400 rpm.
The redline of the SLS is 6500 rpm and 6700 rpm in the STS.
The Northstar engines offer 100,000-mile (160,000-kilometers) durability and limp-home mode in case of total coolant loss. The Northstar’s maintenance-free design allows the car to go up to 100,000 miles before its first scheduled tune-up — only changing the oil, oil filter and air filter. In limp-home mode, the engine can operate on four cylinders at speeds of 50 mph (80 kph) for about 50 miles (80 kilometers), giving the driver an opportunity to reach a safe location. The engine accomplishes this by alternately delivering fuel to four of the eight cylinders. The remaining four cylinders do not fire but continue to pump air, which cools the engine.
On both SLS and STS, the 4T80-E transaxle is linked to the engine via a viscous converter clutch, which assures smooth operation by reducing torque variation when the torque converter clutch is applied. The 4T80-E also features equal-length drive axles, which limit torque steer by minimizing angle differences from side to side as the car accelerates.
***********************
Northstar System
In terms of performance, the Seville SLS and STS feature Cadillac’s widely praised Northstar dual overhead cam V8 engine with the enhanced StabiliTrak 2.0 stability control system, enhanced continuously variable road-sensing suspension, all-speed traction control, ABS and Magnasteer™ speed-sensitive steering.
The 2000 Seville benefits from the next step in modern engine design in the form of an improved Northstar V8. While the basic engine architecture remains a predominantly aluminum 4.6-liter DOHC 32-valve V8, major design improvements have been incorporated to deliver lower emissions, excellent mileage with regular fuel, and smoother, quieter operation.
The list of new Northstar V8 features includes:
* Roller-follower valvetrain design
* Improved combustion chamber configuration
* Center-feed intake manifold
* New pistons
* Coil-on-plug cassette ignition system
* Siemens powertrain control module (engine/transmission control computer)
* Exhaust manifolds with integral air-injection passages
* Flex pipe between the exhaust Y-pipe and the catalytic converter
* Twin electrically driven, two-stage air pumps (LEV applications only)
* Direct mounting of all engine-driven accessories (power steering pump, AC compressor, electrical generator)
* Integrated coolant crossover and throttle-body support
The Seville’s fuel recommendation changes from premium (93 octane, lead-free) to regular, resulting in a major reduction in operating expense. To facilitate this gain, the Northstar’s compression ratio was lowered from 10.3:1 to 10.0:1.
One result of these improvements is that the 2000 Seville will be certified for sale in California and certain Northeast states as a low emissions vehicle (LEV). This was achieved by means of a reaction-heated catalyst, pistons with reduced crevice volume and a new combustion chamber design.
Engine Design Changes
Revised combustion chambers are superior to previous designs in terms of both tumble motion of the incoming fuel-air mixture and burn rate. The intake and exhaust valves have been resized. Larger intake valves improve the engine’s breathing ability, while smaller exhaust valves increase flow velocity, an aid to catalyst light off.
While the new combustion chamber design helps maximize fuel efficiency, even larger gains are made by the addition of roller-follower devices between each cam lobe and valve stem. Compared to the previous Northstar’s direct valve actuation, the result is a substantial reduction in friction. During moderate driving conditions, the torque necessary to turn Northstar’s four camshafts is reduced by 50 percent or more.
The Northstar also benefits from a new ignition system that delivers power to the spark plugs directly instead of through wiring. A cassette containing four ignition coils linked by short secondary leads to adjoining spark plugs now attaches atop each cylinder head cover.
In addition to improved reliability, the new ignition system permits scheduling the magnitude of the voltage sent to the spark plugs. High voltage is used during full-load, high rpm and heavy EGR (exhaust gas recirculation) conditions to guarantee complete combustion. The energy level is reduced to minimize electrical loads and radio frequency interference during light-load conditions, such as medium speed cruising. The result is extended spark-plug life and a peak energy capacity that is 130 percent higher than the system it replaced.
Northstar’s new powertrain control module is a single circuit board device housed within a sealed aluminum case engineered to withstand the harsh underhood environment. The module contains dual microprocessors to monitor and direct engine and transmission operations.
Noise and vibration improvements are the result of adopting a center-feed design for the composite-plastic intake manifold, as opposed to the previous end-feed design. The new design facilitates a near equal-length induction path for all eight cylinders. In contrast, the previous design provided a long path to the front cylinders and shorter paths to rearward cylinders. With the reduction or elimination of many harmonic tones, the resulting induction sound is more of a hum.
A molded-plastic cover backed with acoustical foam rests above the intake manifold to reduce induction, fuel-injector and other noises radiated by the engine. Direct mounting of accessories eliminates flex and vibration inherent with extra brackets. A flexible connection in the exhaust system en route to the catalyst helps quell another source of noise and harshness.
Outstanding Power, Torque
The 4.6-liter dual-overhead-camshaft Northstar V8 installed in the SLS generates 275 horsepower (205 kW) at 5600 rpm and 300 lb.-ft. (407 N•m) of torque at 4000 rpm. The sportier STS is equipped with a retuned version of the Northstar V8 producing 300 horsepower (224 kW) at 6000 rpm and 295 lb.-ft. (400 N•m) of torque at 4400 rpm.
The redline of the SLS is 6500 rpm and 6700 rpm in the STS.
The Northstar engines offer 100,000-mile (160,000-kilometers) durability and limp-home mode in case of total coolant loss. The Northstar’s maintenance-free design allows the car to go up to 100,000 miles before its first scheduled tune-up — only changing the oil, oil filter and air filter. In limp-home mode, the engine can operate on four cylinders at speeds of 50 mph (80 kph) for about 50 miles (80 kilometers), giving the driver an opportunity to reach a safe location. The engine accomplishes this by alternately delivering fuel to four of the eight cylinders. The remaining four cylinders do not fire but continue to pump air, which cools the engine.
On both SLS and STS, the 4T80-E transaxle is linked to the engine via a viscous converter clutch, which assures smooth operation by reducing torque variation when the torque converter clutch is applied. The 4T80-E also features equal-length drive axles, which limit torque steer by minimizing angle differences from side to side as the car accelerates.
