摘要 |
Embodiments for injecting air into exhaust ports of an engine are provided. In one example, a multi-cylinder engine method comprises combusting a rich air-fuel mixture, injecting air into a first cylinder's exhaust port and not into a second cylinder's exhaust port during the first cylinder's exhaust stroke, and injecting air into the second cylinder's exhaust port and not into the first cylinder's exhaust port during the second cylinder's exhaust stroke. In this way, injection into each exhaust port may be timed with exhaust release into each exhaust port. |