Exhaust device of six-cylinder engine

1. An exhaust device for a six-cylinder engine in which the first, second, third, fourth, fifth, and sixth cylinders are ignited in that order, the exhaust device comprising:

an exhaust manifold extending from the first, second, third, fourth, fifth, and sixth cylinders, the exhaust manifold comprising:

first, second, third, fourth, fifth, and sixth upstream exhaust pipes extending respectively from the first, second, third, fourth, fifth, and sixth cylinders;

first, second, and third midway exhaust pipes extending respectively from a first joined portion of ends of the first and fourth upstream exhaust pipes, a second joined portion of ends of the second and fifth upstream exhaust pipes, and a third joined portion of ends of the third and sixth upstream exhaust pipes; and

a downstream exhaust pipe connecting extended ends of the first, second, and third midway exhaust pipes to the ambient atmosphere; wherein

the first, second, third, fourth, fifth, and sixth cylinders define banks in a V-configuration, a first one of the banks being defined by the first, third and fifth cylinders, and a second one of the banks being defined by the second, fourth and sixth cylinders, and the first to sixth cylinders are arranged first to sixth axially along a crankshaft of the engine.

2. The exhaust device of a six-cylinder engine according to claim 1 , in combination with an outboard motor, and further comprising an idling exhaust passage connecting a midway part of the exhaust passage in the exhaust manifold to the ambient atmosphere on the surface of water, and a regulating part configured to vary the opening of a part of the exhaust passage on the downstream side of the midway part of the exhaust passage.

3. The exhaust device of a six-cylinder engine according to claim 1 , further comprising a catalyst disposed in an exhaust passage in the exhaust manifold and configured to purify the exhaust, and an air passage configured to supply secondary air to the upstream side of the catalyst in the exhaust passage.

4. The exhaust device of a six-cylinder engine according to claim 3 , wherein the catalyst has a longitudinal length longer than its radial length in the exhaust passage.

5. An engine comprising first, second, third, fourth, fifth, and sixth cylinders, an exhaust manifold extending from the first, second, third, fourth, fifth, and sixth cylinders, the exhaust manifold comprising:

first, second, third, fourth, fifth, and sixth upstream exhaust pipes extending respectively from the first, second, third, fourth, fifth, and sixth cylinders;

first, second, and third midway exhaust pipes extending respectively from a first joined portion of ends of the first and fourth upstream exhaust pipes, a second joined portion of ends of the second and fifth upstream exhaust pipes, and a third joined portion of ends of the third and sixth upstream exhaust pipes; and

a downstream exhaust pipe connecting extended ends of the first, second, and third midway exhaust pipes to the ambient atmosphere; wherein

the first, second, third, fourth, fifth, and sixth cylinders define banks in a V-configuration, a first one of the banks being defined by the first, third and fifth cylinders, and a second one of the banks being defined by the second, fourth and sixth cylinders, and the first to sixth cylinders are arranged first to sixth axially along a crankshaft of the engine.

6. The engine according to claim 5 , in combination with an outboard motor, and further comprising an idling exhaust passage connecting a midway part of the exhaust passage in the exhaust manifold to the ambient atmosphere on the surface of water, and a regulating part configured to vary the opening of a part of the exhaust passage on the downstream side of the midway part of the exhaust passage.

7. The engine according to claim 5 , further comprising a catalyst disposed in an exhaust passage in the exhaust manifold and configured to purify the exhaust, and an air passage configured to supply secondary air to the upstream side of the catalyst in the exhaust passage.

8. The engine according to claim 7 , wherein the catalyst has a longitudinal length longer than its radial length in the exhaust passage.