| General Motors Atlas | |
|---|---|
 | |
| Overview | |
| Manufacturer | General Motors Corporation |
| Also called | Vortec |
| Production | 2002–2012 |
| Layout | |
| Configuration | Straight-4,Straight-5, andStraight-6 |
| Displacement |
|
| Cylinder bore |
|
| Piston stroke | 102 mm (4.02 in) |
| Cylinder block material | Aluminum |
| Cylinder head material | Aluminum |
| Valvetrain | DOHC4 valves x cyl. withVVT |
| Compression ratio | 10.0:1 |
| RPM range | |
| Max. engine speed | 6,300 rpm |
| Combustion | |
| Fuel system | Multi-point fuel injection |
| Fuel type | Gasoline |
| Oil system | Wet sump |
| Cooling system | Water-cooled |
| Output | |
| Power output | 175–291 hp (130–217 kW) |
| Torque output | 185–277 lb⋅ft (251–376 N⋅m) |
| Chronology | |
| Predecessor | |
Atlas is a name for a family ofinlinepiston engines fortrucks fromGeneral Motors, used in theGMT355 andGMT360 platforms. The series debuted in 2002 with theOldsmobile Bravada, and is used in theBuick Rainier, theChevrolet TrailBlazer andColorado, theGMC Envoy andCanyon, theHummer H3,Isuzu Ascender andi-370, and theSaab 9-7X. The engines use GM's Vortec name, withstraight-4,straight-5, andstraight-6 engines all part of the same family, sharing the same manufacturing equipment, rods, pistons, valves, and other parts. They featurecoil-on-plug ignition systems,[1]variable valve timing on theexhaust side,electronic throttle control, and a special oil pan with a pass-through for thehalf shafts infour-wheel drive vehicles. The inclusion of VVT on the exhaust camshaft side allows the Atlas series to meet emissions standards without the use ofEGR, simplifying the engine design and increasing power for a broad power curve. The LL8 shares 75% of its components with the LK5 and L52; while the LK5 and L52 share 89% of their components.[2]
The Atlas engines feature aluminum cylinder blocks and heads, with the cylinder bores featuring replaceable steelcylinder liners.[1] The 4- and 5-cylinder versions feature dual balance shafts,[3][4] which are unnecessary in the 6-cylinder.[5]
The Atlas program began in 1995 along with the planning for GM's next-generation mid-sizeSUVs andpickup trucks. These vehicles were designed around the I6 engine. The I6 version was used in aBaja 1000 racing truck, winning its first race in a class that also includedV8 engines. Another I6-powered truck won the truck class at thePikes Peak International Hillclimb.
The Atlas engines were produced at theFlint Engine South plant inFlint, Michigan, while the I4 and I5 versions were produced at theTonawanda Engine plant inTonawanda, New York, nearBuffalo.
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TheLL8 (orVortec 4200), is astraight-6 gasoline engine produced from 2002 to 2009. It was the first Atlas engine, and was introduced in 2002 for theChevrolet TrailBlazer,GMC Envoy, andOldsmobile Bravada. The engine was also used in theBuick Rainier,Saab 9-7X, andIsuzu Ascender.
It displaces 4.2 L (4,160 cc; 253.9 cu in), with a 93 mm × 102 mm (3.66 in × 4.02 in) bore and stroke. It has four valves per cylinder, dual-overhead cams (DOHC), andvariable valve timing on the exhaust cam, a first for GM inline engines. When introduced, this engine's power was 270 hp (201 kW) at 6,000rpm and torque was 275 lb⋅ft (373 N⋅m) at 3,600 rpm. 2003 saw a slight bump in power to 275 hp (205 kW), while torque was unchanged. For 2006, power was increased to 291 hp (217 kW) at 6,000 rpm and torque to 277 lb⋅ft (376 N⋅m)) at 4800 rpm with the addition of aMAF and a complete internal redesign of the engine; however, due to the newSAE rating procedures, ratings can vary slightly between years. The engine redline is 6,300 rpm. TheLL8 was on theWard's 10 Best Engines list for 2002 through 2005 and was the basis for all the otherAtlas engines. With the closure of theMoraine, Ohio, plant and the discontinuation of theGMT360 platform (Chevrolet TrailBlazer, GMC Envoy, etc.), production of theLL8 also ended.[6]
Applications:
TheLLR (also calledVortec 3700), is astraight-5DOHC engine produced from 2007 through 2012. It displaces 3.7 L (3,653 cc; 222.9 cu in), courtesy of a larger 95.5 mm (3.76 in) bore while keeping the 102 mm (4.02 in) stroke. TheLLR also corrected the head issue found in theL52. It produces 242 hp (180 kW) at 5,600rpm and 242 lb⋅ft (328 N⋅m) at 4,600 rpm. The engine redline is 6,300 rpm.[6]
Applications:
TheL52 (also calledVortec 3500), is astraight-5DOHC engine produced from 2004 through 2006. It displaces 3.5 L (3,460 cc; 211.1 cu in), with a 93 mm × 102 mm (3.66 in × 4.02 in) bore and stroke.Dynoed at theflywheel it produces 220 hp (164 kW) at 5,600rpm and 225 lb⋅ft (305 N⋅m) at 2,800 rpm. The engine redline is 6,300 rpm.[4]
Applications:
TheLLV (also calledVortec 2900) is a 2.9 L; 178.3 cu in (2,921 cc)straight-4DOHC engine produced between 2007 and 2012, with a 95.5 mm × 102 mm (3.76 in × 4.02 in) bore and a stroke. It replaced theLK5 and produced 185 hp (138 kW) at 5,600rpm and 190 lb⋅ft (258 N⋅m) of torque at 2,800 rpm. The engine redline is 6,300 rpm.[7]
Applications:
TheLK5 (also called theVortec 2800) is a 2.8 L; 169.0 cu in (2,770 cc)straight-4DOHC engine produced between 2004 and 2006, with a 93 mm × 102 mm (3.66 in × 4.02 in) bore and stroke. It produces 175 hp (130 kW) at 5,600rpm and 185 lb⋅ft (251 N⋅m) of torque at 2,800 rpm. The engine redline is 6,300 rpm.[3]
Applications:
