Northstar engine series

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Northstar engine
Cadillac 4.6 L DOHC V8 engine.jpg
4.6 L Northstar engine
Overview
Manufacturer General Motors
Also called Cadillac Northstar
Production 1991–2010
Combustion chamber
Configuration DOHC 90° V8/V6
Chronology
Predecessor
Successor

The Northstar engine series of automobile engines is General Motors' most technically complex 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 did expand with longitudinal and 4.4 L supercharged versions. The Northstar name was used outside Cadillac as well, with Pontiac and Buick versions carrying that moniker.

Pre-2003 Northstar engines have been noted for having headgaskets that are prone to failure, often requiring replacement of the engine. A new patented cylinder head stud is on the market to repair these engine blocks, so owners no longer need to replace the engine- they can now simply repair it. GM ceased production of the Northstar engine in July 2010. Production of the final cars to include the engine, the Cadillac DTS, Buick Lucerne, and Cadillac STS, ended in 2011.[1] Newer Cadillac V8 models like the CTS-V use the GM small-block OHV engine, marking a return to simpler engine design.

Development and features[edit]

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 because the c.a.f.e ratings for 1982 would not allow for the use of the V8-6-4 of 1981. At the time it was GM's corporate policy not to pass the gas guzzler tax on to the consumer.

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, and new to the luxury car market 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.

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 silicone 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 cast aluminum pistons included valve clearance. Northstar is an interference engine, with bronze pin bushings and free-floating piston pins.

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 are magnesium for light weight.

Eight thermoplastic tubes were used in the induction system, leading to sequential fuel injection. The engine used a distributorless ignition system with a waste spark setup. 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 "limp home" fail-safe mode which allowed the engine to continue running for a limited time without any coolant. Supplying fuel to only one cylinder bank in turn, the engine would "air cool" the inactive bank. This technique, combined with its all-aluminum construction and large oil capacity, allows the engine to maintain safe temperatures, allowing a Northstar-equipped car to be driven with no coolant for about 100 mi (161 km) without damage. However, the head gaskets are prone to leak, causing loss of some coolant, and high engine temperatures. It is not enough to cause the fail-safe mode so the high temperature can cause the block to crack.

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 direct coil-on-plug ignition, and variable valve timing, which can vary intake by up to 40° and the exhaust by up to 50°. VVT 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[edit]

The engine was introduced in mid-1992 in the 1993 Cadillac Allanté, eventually ended up in most Cadillac automobiles, but is now phased out of all 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 2004-2005 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 had killed the idea.

Most Northstar engines produce 275 hp (205 kW) to 320 hp (239 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 Northstars displaced 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[who?] 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, although only in the Cadillac DTS, since it was announced that the final production year of the STS will use the 3.6L V6 engine only.

The Northstar System included the following components:

    • L37 high-output 300 hp (224 kW) and 295 lb·ft (400 N·m)
    • LD8 high-torque 275 hp (205 kW) and 300 lb·ft (407 N·m)
  • GM 4T80-E 4-speed automatic transmission
  • Road Sensing Suspension
RSS was available in both standard and CV-RSS (continuously-variable) systems. It monitored damping rates of the shock absorbers every 15 milliseconds, selecting between two settings.
Magnasteer combines conventional hydraulic power steering and magnetized "doughnuts" mounted around the output shaft, which stiffen the steering as vehicle speed increases.

The later versions of the Northstar engine included 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[edit]

The L37 (VIN "9") was the original North star. It is tuned for responsiveness and power, while the later LD8 is designed for more sedate use. The L37 code had been used on all high-output transverse Northstars, even as the exact engine specifications evolved. Its displacement is 4600cc. The compression ratio for the L37 is 10.3:1 for engines built prior to 2000, and 10:1 for those built afterwards. 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.[citation needed] 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:

Year Model Power Torque
1993 Cadillac Allanté 295 hp (220 kW) @ 5600 rpm 290 lb·ft (393 N·m) @ 4400 rpm
1993–1994 Cadillac Eldorado ETC 295 hp (220 kW) @ 5600 rpm 290 lb·ft (393 N·m) @ 4400 rpm
1995–2002 Cadillac Eldorado ETC 300 hp (224 kW) @ 6000 rpm 295 lb·ft (400 N·m) @ 4400 rpm
1993 Cadillac Seville STS 295 hp (220 kW) @ 5600 rpm 290 lb·ft (393 N·m) @ 4400 rpm
1994–2004 Cadillac Seville STS 300 hp (224 kW) @ 6000 rpm 295 lb·ft (400 N·m) @ 4400 rpm
1996–2004 Cadillac DeVille Concours/DTS 300 hp (224 kW) @ 6000 rpm 295 lb·ft (400 N·m) @ 4400 rpm
2005 Cadillac DeVille DTS 290 hp (216 kW) @ 5600 rpm 285 lb·ft (386 N·m) @ 4400 rpm
2006–2011 Cadillac DTS Performance 292 hp (218 kW) @ 6300 rpm 288 lb·ft (390 N·m) @ 4500 rpm
2008–2011 Buick Lucerne Super 292 hp (218 kW) @ 6300 rpm 288 lb·ft (390 N·m) @ 4500 rpm

LD8[edit]

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 had been used on all torque-tuned transverse Northstars, even as the exact engine specifications evolved. Compression ratio is 10.3:1 for engines built prior to model year 2000, and 10:1 for those built afterwards.

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).

Year Model Power Torque
1994 Cadillac Eldorado 270 hp (201 kW) 300 lb·ft (407 N·m)
1995–2001 Cadillac Eldorado 275 hp (205 kW) @ 5750 rpm 300 lb·ft (407 N·m)
2002 Cadillac Eldorado 275 hp (205 kW) @ 5600 rpm 300 lb·ft (407 N·m) @ 4000 rpm
1994 Cadillac Seville SLS 270 hp (201 kW) 300 lb·ft (407 N·m)
1995–2004 Cadillac Seville SLS 275 hp (205 kW) @ 5600 rpm 300 lb·ft (407 N·m) @ 4000 rpm
1994 Cadillac DeVille Concours 270 hp (201 kW) 300 lb·ft (407 N·m)
1995 Cadillac DeVille Concours 275 hp (205 kW) @ 5750 rpm 300 lb·ft (407 N·m)
1996–2001 Cadillac DeVille 275 hp (205 kW) @ 5750 rpm 300 lb·ft (407 N·m) @ 4000 rpm
2002–2005 Cadillac DeVille 275 hp (205 kW) @ 5600 rpm 300 lb·ft (407 N·m) @ 4000 rpm
2006–2011 Cadillac DTS 275 hp (205 kW) @ 6000 rpm 295 lb·ft (400 N·m) @ 4400 rpm
2004–2005 Pontiac Bonneville GXP 275 hp (205 kW) @ 5600 rpm 300 lb·ft (407 N·m) @ 4000 rpm
2006–2007 Buick Lucerne CXS 275 hp (205 kW) @ 6000 rpm 295 lb·ft (400 N·m) @ 4400 rpm

LH2[edit]

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 STS, SRX, and XLR, as well as receiving continuously variable valve timing on both intake and exhaust sides. The RWD (LH2) Northstar produces 320 hp (239 kW) and 315 lb·ft (427 N·m). An increased compression ratio of 10.5:1 enables most of the increase in power from the L37 and LD8 Northstars.

Year Model Power Torque
2004–2009 Cadillac SRX 320 hp (239 kW) @ 6400 rpm 315 lb·ft (427 N·m) @ 4400 rpm
2004–2009 Cadillac XLR 320 hp (239 kW) @ 6400 rpm 310 lb·ft (420 N·m) @ 4400 rpm
2005–2010 Cadillac STS 320 hp (239 kW) @ 6400 rpm 315 lb·ft (427 N·m) @ 4400 rpm

Supercharged LC3[edit]

A 4.4 L (266 cu in) supercharged Northstar was used in the 2006 Cadillac STS-V and Cadillac XLR-V. The bore was reduced for increased strength and improved head gasket sealing. Variable valve timing is used on both the intake and exhaust sides. The STS-V engine produces 469 hp (350 kW) at 6400 rpm and 439 lb·ft (595 N·m) at 3900 rpm with 9:1 compression and the XLR-V engine produces 443 hp (330 kW) at 6400 rpm and 414 lb·ft (561 N·m) at 3900 rpm.

Year Model Power Torque
2006–2009 Cadillac STS-V 469 hp (350 kW) @ 6400 rpm 439 lb·ft (595 N·m) @ 3900 rpm
2006–2009 Cadillac XLR-V 443 hp (330 kW) @ 6400 rpm 414 lb·ft (561 N·m) @ 3900 rpm

L47[edit]

An L47 inside an Aurora's engine bay

The L47 Aurora engine was a special V8 designed for the Oldsmobile Aurora, based on the Northstar engine. It is a DOHC 3,995 cc (3.995 L; 243.8 cu in) V8 which produced 250 horsepower (186 kW) and 260 lb·ft (353 N·m) of torque. The bore was 87 mm (3.4 in) and the stroke was 84 mm (3.3 in). The L47 had a 10.3:1 compression ratio and used premium fuel.

An early version or prototype of this engine was used in the 2nd generation Oldsmobile Aerotech.

Although most of the Northstar's features, including the coolant loss system, remained intact, the decreased bore increased weight unacceptably. To reduce it, Oldsmobile used a one-piece glass-filled thermoplastic intake manifold and simplified AC Rochester sequential fuel injection. A new die-cast structural aluminum oil pan incorporated baffling to reduce oil starvation in hard driving. A starter interlock prevented the starter from engaging if the quiet L47 was already running.

A highly modified 650 hp (485 kW) version of this engine was used by General Motors racing division initially for Indy Racing League competition starting in 1997, then was later used in the Cadillac Northstar LMP program in 2000. Both engines retained the 4.0 L capacity, but the Northstar LMP version was twin-turbocharged.[2]

The Aurora was also used in the Shelby Series 1 car.

The Aurora engine was introduced in 1994 for the 1995 model year, and General Motors has not used this engine since the demise of the marque in 2004.

Year Model Power Torque
1995–2003 Oldsmobile Aurora 250 hp (186 kW) @ 5600 rpm 260 lb·ft (353 N·m) @ 4400 rpm
1999–2005 Shelby Series 1 320 hp (324 PS) @ 6500 rpm 290 lb·ft (390 N·m) @ 5000 rpm

LX5 (Shortstar)[edit]

The LX5 V6 is a DOHC engine from Oldsmobile, introduced in 1999 with the Oldsmobile Intrigue. It was produced by the Premium engine group at GM and was thus called the Premium V6, or PV6, while it was being developed. It is based on the L47 Aurora V8, which is itself based on the Northstar engine, so engineers called it the Short North, though Oldsmobile fans have taken to calling it the Shortstar.

It is not a simple cut-down V8. Although it has a 90° vee-angle like the Northstar and Aurora, the engine block was engineered from scratch, so bore centers are different. It has chain-driven dual overhead cams and four valves per cylinder, but is an even-firing design with a split-pin crankshaft similar to the Buick 3800 engine. The LX5 displaced 3,473 cc (3.473 L; 211.9 cu in) and produced 215 hp (160 kW) @ 5,600 rpm and 234 lb·ft (312 N·m) @ 4,400 rpm. Bore is 89.5 mm (3.52 in) and stroke is 92 mm (3.6 in). It was also one of GM's first engines to use coil-on-plug ignition. Compression ratio is 9.3:1.

The cost of building this engine was high, and it was not used in many vehicles. It was said at the time that a family of premium V6s would follow, with displacements ranging from 3.3 L to 3.7 L, but only the LX5 was ever produced before GM axed the Shortstar in favor of their current flagship V6, the High Feature, in 2004.

The LX5 was entirely different from any other V6 in the GM inventory - the only other DOHC V6 engines ever offered by GM include the troublesome-to-maintain Chevrolet Twin Dual Cam produced from 1991-1997 (which was made by heavily modifying the traditional Chevy 60-degree OHV block for the dual overhead cams rather than building a DOHC engine from the ground up), and the Cadillac/Holden HFV6 available from 2004 to the present day. These three designs are completely unrelated and oddly enough leave two gaps in 1998 and 2003 where no DOHC V6 was available from GM. (Except for the 54 degree Opel V6 used most notably in the first generation Cadillac CTS at launch as well as the Saturn L Series.) This contrasts starkly with competitors practices of evolving engineering over multiple, continuously improving designs.

As with the Aurora V8, production stopped with the demise of Oldsmobile.

Year Model Power Torque
1999–2002 Oldsmobile Intrigue 215 hp (160 kW) @ 5600 rpm 234 lb·ft (317 N·m) @ 4400 rpm
2001–2002 Oldsmobile Aurora 215 hp (160 kW) @ 5600 rpm 234 lb·ft (317 N·m) @ 4400 rpm

The 3.5L LX5 was on the Ward's 10 Best Engines list for 1999 and 2000.

See also[edit]

Notes[edit]

  1. ^ "Sitemap". Autoblog. Retrieved 2012-06-04. 
  2. ^ Weitzman, Larry (2001).The Aurora by Oldsmobile (2001), Better in every respect. Autochannel. Retrieved on June 28, 2009.

References[edit]

  • Frank Markus. "1993 Technical Highlights". Car and Driver (October 1992): 59–60. 
  • "Technical Highlights". Car and Driver (October 1993): 115. 
  • Joel D. Pietrangelo. "Northstar is heart of Allante re-do for '93 - V-8 engine, General Motors' Cadillac Motor Car Div.'s new model roadster". Ward's Auto World (February 1992). 

External links[edit]