GM Premium V engine

Infobox Automobile engine
name=GM Premium V
aka=Cadillac Northstar
manufacturer=General Motors
production=1991–
class=DOHC 90° V8/V6
predecessor=Cadillac HT V8
LQ1 V6
similar=Jaguar AJ-V8
Ford Modular V8
Ford/Yamaha V8
Chrysler PowerTech V8
Mercedes-Benz M113/M115
BMW M62/S62
BMW N62
Toyota UZ
Nissan VH
Nissan VKThe Premium V family 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. Alfa Romeo is rumored to be another future user of the Premium V in the US-market Kamal.

Development and features

The Premium V 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 Convert| 300|hp|kW|0|abbr=on, the Northstar featured a unique die-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 8.5 quarts.

Cast-iron cylinder liners were specified and the forged aluminum pistons included valve clearance, making Northstar a non-interference engine, with bronze pin bushings and free-floating piston pins used.

The one-piece cast aluminum cylinder heads extend around the "maintenance-free" cam-drive chain case. Direct-acting hydraulic valves are used 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. Direct ignition was a novelty for the time, with an electronic system adjusting 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

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.

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 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 to 315 hp (205 to 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, these revisions allowed the engines to run strictly on regular grade gasoline.

All but the supercharged Northstar displace 4.6 L (4565 cc/279 in³) with a 93 mm (3.66 in) bore and 84 mm (3.31 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 (4371 cc/266 in³). 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.

L37

The L37 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. Compression ratio for the L37 is 10.0:1, shared with the LD8.

The original L37 was specified at Convert|290|hp|kW|0|abbr=on, but 1993 production examples were rated at Convert|295|hp|kW|0|abbr=on. The engine topped out at Convert|300|hp|kW|0|abbr=on 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 domestic title still belonging to the 1970 Cadillac Eldorado with 400 hp (500 in³, 8.2 L) (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).

Vehicles using the L37 include:

upercharged LC3

A 4.4 L (4371 cc/266 in³) supercharged Northstar is 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 ft·lbf (595 N·m) at 3900 rpm with 9.0:1 compression and the XLR-V engine produces 443 hp (330 kW) at 6400 rpm and 414 ft·lbf (561 N·m) at 3900 rpm .

L47

. The bore is 87 mm and the stroke is 84 mm. The L47 has a 10.3:1 compression ratio and uses premium fuel.

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 prevents the starter from engaging if the quiet L47 is already running.

A highly modified version of this engine was used by General Motors racing division initially for Indy Racing League competition starting in 1995, 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.

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.

LX5

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 4 valves per cylinder, but is an even-firing design with a split-pin crankshaft similar to the modern GM 3800 engines. The LX5 displaced 3.5 L (3473 cc) and produced 215 hp (160 kW) and 230 ft·lbf (312 N·m). Bore is 89.5 mm and stroke is 92 mm. 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. It was entirely different from any other V6 in the GM inventory, and as with the Aurora V8, production stopped with the demise of Oldsmobile.

This engine was used in the following:
* 1999-2002 Oldsmobile Intrigue
* 2001-2002 Oldsmobile Aurora

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

References

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See also

* GM High Feature engine
* Cadillac V8 engine
* List of GM engines

External links

* [http://www.autospeed.com/cms/A_1569/article.html Technical article from AutoSpeed]
* [http://waw.wardsauto.com/ar/auto_general_motors_corp_3 Ward's article]