Which of the following statements is incorrect about using a weak mixture?

Using a weak mixture in an engine typically refers to a condition where there is a higher ratio of air to fuel in the combustion process. One of the key effects of this condition is that the charge within the combustion chamber can burn slower. This is primarily due to the increased presence of nitrogen, which does not participate in combustion, effectively diluting the fuel-air mixture. As a result, the combustion temperature is lower, potentially leading to incomplete combustion and longer ignition times.

When operating on a weak mixture, it may also be necessary to adjust the ignition timing. Advancing the ignition timing can help promote more efficient combustion despite the slower burn rate associated with a weak mixture. This adjustment compensates for the extended time it takes for the mixture to ignite fully, ensuring that the maximum pressure occurs at the optimal point in the power stroke. On the other hand, retarding the ignition timing in this scenario would likely exacerbate issues with combustion efficiency, leading to reduced engine performance.

Thus, when considering the effect of using a weak mixture, the ignition timing may need to be advanced rather than retarded. This is why indicating that ignition may need to be retarded in this context is incorrect.