Which statement is true about CAC restriction and piston crown cracking?

• A. Externally restricted CAC can cause cracks
• B. Internally restricted CAC can cause cracks
• C. Both externally and internally restricted CAC can cause cracks
• D. Neither restriction causes cracks

Answer: (A)

Restriction on the air path outside the charge air cooler directly reduces the amount of cooled, high-temperature air reaching the engine, so the charge entering the cylinder remains hotter. Hot intake air raises the combustion temperature and increases thermal stress on the piston crown through repeated heat cycling, making cracking more likely over time. The externally restricted path thus creates a clearer link to piston crown cracking because the cooling of the charge air is compromised in a way that drives higher peak temperatures in the cylinder. Internal restrictions, while they can affect flow and pressure, don’t as directly translate to the same level of increased charge-air temperature entering the cylinder, so the connection to crown cracking is less direct.