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The Northstar engine series of automobile engines was 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 went out of production in 2003, 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. 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. 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 == GM initiated the Northstar's design 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 GM pushed hastily into production because the CAFE standards 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 luxury cars like Lexus, Acura, and Infiniti. GM developed a laundry list of items to be included in these new models, including sophisticated steering, braking, and suspension technologies. This 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 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. GM specified cast-iron cylinder liners and the cast aluminum pistons included valve clearance. Northstar is an interference engine, the valves will strike the pistons if they lose timing. It has bronze piston pin bushings and free-floating piston pins. GM used cast aluminum cylinder heads featuring 4 valves per cylinder. The heads used dual overhead cams 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 and sound damping. Eight thermoplastic tubes were used in the induction system, providing for sequential fuel injection. The engine used a distributorless ignition system with a waste spark setup. The PCM (powertrain control module) 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. These high temperatures are not enough to cause the engine to enter fail-safe mode so they 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Northstar engine series」の詳細全文を読む スポンサード リンク
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