| Σ engine Sigma engine | |
| Manufacturer: | Hyundai Motor Company |
| Production: | 1989–2007 |
| Configuration: | V6 |
| Block: | Cast iron |
| Head: | Aluminum |
| Valvetrain: | SOHC, DOHC 4 valves x cyl. |
| Fueltype: | Gasoline LPG |
| Fuelsystem: | Multi-port fuel injection |
| Coolingsystem: | Water-cooled |
| Displacement: | 2497cc 2972cc 3497cc |
| Bore: | 83.52NaN2 91.12NaN2 932NaN2 |
| Stroke: | 762NaN2 85.82NaN2 |
| Power: | NaN0NaN0 |
| Torque: | NaNkgm |
| Successor: | Hyundai Lambda engine |
The Hyundai Sigma engine is a series of V6 piston engines from Hyundai Motor Company, based on the Mitsubishi 6G7 engine. The Sigma engine family began life with the simple V6 name. Displacement ranges from 2497to.
The DOHC G6AV (also called the 2.5 D) is the small 24971NaN1 version. Bore is 83.52NaN2 and stroke is shared with the 2972cc at 762NaN2. Output is 162- at 6,000 rpm and 20.8- at 4,500 rpm.
The DOHC G6AT and G6CT (also called the 3.0 D) both displace 29721NaN1. They share the 2.5's 762NaN2 stroke but use a larger 91.12NaN2 bore. Output for the older G6AT is 185- at 6,000 rpm and 24.6- at 4,000–4,500 rpm, while the G6CT produces 187- at 5,500–6,000 rpm and 26.5- at 3,500–4,000 rpm.
The older SOHC G6AT 3.0 S produces just 141- at 5,000 rpm and 22.9- at 2,500–3,000 rpm.
The L6AT displace 29721NaN1. They share the 2.5's 762NaN2 stroke but use a larger 91.12NaN2 bore. Output is 1350NaN0 at 4,500 rpm and 23- at 2,500 rpm.
The G6AU and G6CU (both also called the 3.5 D ) are the large 34971NaN1 versions of the Sigma engine. Bore and stroke are both larger at NaN2NaN2, respectively. Output is 203- at 5,500 rpm and 29.6- at 4,000 rpm for the older G6AU and 195- at 5,500–6,000 rpm and 30- at 3,500 rpm for the newer G6CU.
The 3.5 D has a cast iron engine block and aluminum DOHC cylinder heads. It uses Multi-port fuel injection, has 4 valves per cylinder, and features forged steel connecting rods. It is designed to run on "regular" unleaded gasoline rather than the premium fuel used in many other high-output V6 engines.
The US-market version produces 1970NaN0 at 5,500 rpm with 30.3kgm of torque at 3,500 rpm. It was introduced with the Kia Sedona minivan in 2001.