The Northstar engine series of automobile engines is General Motors' modern 90° V engine architecture. The family is most associated with Cadillac's Northstar V8, but the family has also seen use at Oldsmobile (as the Aurora L47 V8 and "Shortstar" LX5 ). The Oldsmobile variants are no longer in production, but the Northstar family has expanded with new longitudinal and 4.4 L supercharged versions. The Northstar name is now used outside Cadillac as well, with the Pontiac and Buick versions now carrying that moniker.
Development and features
The Northstar's design was initiated as a response to the advanced dual overhead cam V8 engines introduced by European and Japanese competitors of Cadillac in the late 1980s. At that time, Cadillac was using the aluminum HT Overhead Valve (OHV) V8 which had been pushed hastily into production after the failure of the V8-6-4 of 1981.
Cadillac was developing new models like the Allanté and updated Eldorado and Seville STS which they hoped would compete against the best from BMW, Mercedes-Benz, Lexus, and Infiniti. They developed a laundry list of items that must be included in these new models, including sophisticated steering, braking, and suspension technologies, which became known as the Northstar System . One key element was a high-tech V8 engine with all of the features and performance of the competitors' offerings.
The "Northstar" V8, as it was then known, was an evolution of the Lotus-designed Chevrolet LT5 all-aluminum DOHC 32-valve V8 used in the Corvette ZR-1. Archrival Ford Motor Company was developing a similar engine at that time as well, and Ford's Modular engine would precede the Northstar into production with its introduction on the 1991 Lincoln Town Car. Both continue in production at 4.6 L of displacement.
Capable of producing 300 hp (224 kW) out of its 4565 cc displacement, the Northstar featured a cast aluminum 90° V8 block with 102 mm (4 in) bore spacing split into unitary upper and lower halves. The lower crankcase assembly supported the crankshaft without conventional main bearing caps. An oil manifold plate with an integrated silicon gasket forms the oil gallery under this. A typical oil change used 7.5–8 quarts of oil.
Cast-iron cylinder liners were specified and the forged aluminum pistons included valve clearance. Northstar is a interference engine, with bronze pin bushings and free-floating piston pins used.
Cast aluminum cylinder heads were used featuring 4 valves per cylinder. The heads used dual overhead cams which are driven through the "maintenance-free" cam-drive chain case. The cams act directly on hydraulic lifters on the ends of the valves and are fed with a lubrication passage drilled through the cylinder head lengthwise. The intake valves are inclined at 25°, while the exhaust valves are canted to 7° with center-mounted platinum-tipped spark plugs. The cam covers were fabricated from magnesium for light weight.
Eight thermoplastic tubes were used in the induction system, leading to sequential fuel injection. The engine uses a direct ignition system with a single coil per cylinder and no distributor. The PCM controls spark and fuel injection timing as well as the shift points for the new 4T80-E transmission.
One notable feature, advertised at the time, was the fail-safe cooling mode which allowed the engine to continue running for a limited time without any coolant at all. It alternated banks of cylinders, basically "air cooling" the inside of the cylinders, to maintain cool temperatures, allowing a Northstar-equipped car to be driven with no coolant for about 100 mi (161 km) with no damage.
Another unusual feature of some Northstar-equipped cars is a liquid-cooled alternator used on Cadillac's Seville, DeVille, and Eldorado. The liquid-cooling helped prolong the life of the alternator in these electronic-laden models, though GM reverted to a traditional air-cooled setup for 2001 to eliminate potential leak points and extraneous tubing.
All engines of this family share the same Northstar bellhousing pattern.
Later developments included variable valve timing, which can vary intake by up to 40° and the exhaust by up to 50°. This system was devised for the longitudinal LH2 version, and has not, to date, been used on the transverse front wheel drive engines due to packaging considerations.
Northstar series
The engine was introduced in mid-1992 in the 1993 Cadillac Allanté and continues to be used in most Cadillac models. The original Northstar Allanté also introduced the Northstar System which included traction control, adaptive suspension, and antilock brakes. Early Northstar required premium grade gasoline to run safely.
The Northstar was sold exclusively by Cadillac for over a decade before being introduced in the 2004 Pontiac Bonneville and 2006 Buick Lucerne. However, the 4.0L L47 V8 variant was used in the Oldsmobile Aurora and the 3.5L LX5 V6 in the Oldsmobile Intrigue. The engine received a forged steel crankshaft in October 2003. Cadillac had planned to introduce a V12 Northstar this decade, likely for use in the Escalade, but economics and new CAFE standards have killed this idea.
Most Northstar engines produce 275 hp (205 kW) to 315 hp (235 kW). The engines were revised for 2000 with coil-on-plug ignition and roller follower valvegear for improved fuel economy and reduced emissions. Though power output did not change, this update eliminated the need for premium fuel.
All but the supercharged Northstar displace 4.6 L (279 cu in) with a 93 mm (3.7 in) bore and 84 mm (3.3 in) stroke. For better head gasket sealing between cylinders, the supercharged version is de-bored to 91 mm (3.6 in) for a total displacement of 4.4 L (266 cu in) . The block is said to be capable of expansion up to 5.4 L, though no such engine has been produced.
The Northstar was on the Ward's 10 Best Engines list for 1995, 1996, and 1997.
The Northstar System was Cadillac's trademarked name for a package of automobile performance features. Introduced in mid 1992 on the 1993 Cadillac Allanté and later on that year's Seville and Eldorado, the Northstar name continues in use to this day.
The Northstar System included the following components:
- L37 high-output 300 hp (224 kW) and 295 ft·lbf (400 N·m)
- LD8 high-torque 275 hp (205 kW) and 300 ft·lbf (407 N·m)
- GM 4T80-E 4-speed automatic transmission
- Road Sensing Suspension
- 4-wheel disc brakes with Bosch antilock brakes
- Magnasteer speed-variable power steering
The latest versions of the Northstar engine include the 4.6L 320 hp (239 kW) and 315 lb·ft (427 N·m) LH2 which began in 2004, and supercharged 4.4L 469 hp (350 kW) LC3 created for the STS-V which are detailed below.
General Motors employed a continuously variable system for the Cadillac Northstar System, VVT (Variable Valve Timing). The Northstar VVT provides a continuously variable system throughout the RPM range, increasing fuel economy. GM engines use the double overhead cam, varying both intake and exhaust for better performance.
L37
The L37 (VIN "9") was the original Northstar. It is tuned for responsiveness and power, while the later LD8 is designed for more sedate use. The L37 code has been used on all high-output transverse Northstars, even as the exact engine specifications evolved. Its displacement is 4600cc flat the compression ratio for the L37 is 10:1, shared with the LD8.
The original L37 was specified at 290 hp (216 kW), but 1993 production examples were rated at 295 hp (220 kW). The engine topped out at 300 hp (224 kW) from 1996 through 2004 on the STS, DTS and ETC models, making these some of the most powerful domestic front wheel drive cars ever built, the most powerful title still belonging to the 1970 Cadillac Eldorado 500 cu in (8.2 L) with 400 hp (298 kW) (although the latter's rating is in the older SAE gross horsepower system, figured without accessories or muffler, where the current engine outputs are as-installed, net ratings). For 2005 the high output Northstar became Northstar NHP, and was downrated to 290 horsepower (220 kW) under the new SAE certified horsepower rating system. In 2006, the updated DTS "Performance Package" model got a slight bump to 292 hp (218 kW). Vehicles using the L37 include:
LD8
The LD8 (VIN "Y") is a transverse V8 for front-wheel drive cars. Introduced in 1994, it is designed to provide more torque than the high-revving L37. The LD8 code has been used on all torque-tuned transverse Northstars, even as the exact engine specifications evolved. Compression ratio is 10:1.
The 1998 revision is quieter than previous Northstar engines, due to hydraulic engine mounts, and performs better due to a tuned intake system.
Most LD8 Northstars are rated at 275 hp (205 kW) and 300 lb·ft (407 N·m).
LH2
The Northstar was designed originally for transverse front-wheel drive applications. It was modified substantially in 2004 for longitudinal rear- and all-wheel drive use in the SRX and XLR, as well as receiving continuously variable valve timing on both in
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