Twin scroll turbocharger in a variable displacement engine
Methods and systems are provided for operating an engine with variable displacement engine (VDE) operation coupled to a twin scroll turbocharger. One method comprises directing exhaust from a first outer cylinder and a first inner cylinder of four cylinders to a first scroll of the twin scroll turbocharger, directing exhaust from a second outer cylinder and a second inner cylinder of the four cylinders to a second scroll of the twin scroll turbocharger, and during a first condition, firing all four cylinders with uneven firing.
1. A method for a boosted engine having VDE operation and a twin scroll turbocharger with first and second exhaust turbine scrolls, comprising:
when all cylinders of an inline group of cylinders including a first outer cylinder adjacent to a first inner cylinder and a second inner cylinder adjacent to a second outer cylinder are activated, firing the second inner cylinder at 120 degrees of crank rotation and flowing exhaust from the second inner cylinder to the second scroll, firing the first inner cylinder at 240 degrees of crank rotation after firing the second inner cylinder and flowing exhaust from the first inner cylinder to the first scroll, firing the second outer cylinder at 240 degrees of crank rotation after firing the first inner cylinder and flowing exhaust from the second outer cylinder to the second scroll, and firing the first outer cylinder at 120 degrees of crank rotation after firing the second outer cylinder and flowing exhaust from the first outer cylinder to the first scroll.
2. The method of claim 1 further comprising, when the first outer cylinder is deactivated and the first inner, second inner, and second outer cylinders are activated, firing the activated cylinders at 240 crank angle degree intervals, flowing exhaust from the first inner cylinder to the first scroll, and flowing exhaust from the second inner and second outer cylinders to the second scroll.
3. The method of claim 2 , wherein the first outer cylinder is deactivated and the first inner, second inner, and second outer cylinders are activated during idle engine conditions.
4. The method of claim 2 , wherein the first outer cylinder is deactivated and the first inner, second inner, and second outer cylinders are activated during medium engine load conditions.
5. The method of claim 1 further comprising, when the second outer and second inner cylinders are deactivated and the first outer and first inner cylinders are activated, firing the activated cylinders at 360 crank angle degree intervals and flowing exhaust from the activated cylinders to the first scroll.
6. The method of claim 5 , wherein the second outer and second inner cylinders are deactivated and the first outer and first inner cylinders are activated during low engine load conditions.