6. Which of the following statements concerning the factors affecting ignition delay is correct?

Increased coolant temperature decreases ignition delay by raising cylinder wall and air temperatures, bringing the fuel-air charge closer to auto-ignition conditions. Ignition delay is the time between fuel injection and combustion; higher temperatures and pressures shorten this delay. Increased intake air temperature and compression ratio reduce, not increase, ignition delay. Combustion chamber turbulence reduces ignition delay by improving mixing and heat transfer.