Question 141Motor Plants - 1st Asst/Chief

The correct answer is A) An increase in coolant temperature will decrease ignition delay. The reasoning behind this is that an increase in coolant temperature leads to higher cylinder temperatures, which in turn reduces the time required for the air-fuel mixture to self-ignite. This is due to the faster vaporization and mixing of the fuel, as well as the higher temperature of the compressed air-fuel charge at the time of injection. The other options are incorrect because: B) An increase in intake air temperature would actually decrease ignition delay, not increase it; C) An increase in compression ratio would decrease ignition delay by raising the temperature and pressure of the air-fuel mixture; and D) An increase in combustion chamber turbulence would typically improve fuel-air mixing and decrease ignition delay, not increase it.