Which engine model features an EGR cooler and coolant collector cast as one piece?

The engine model that features an EGR cooler and coolant collector cast as one piece is indeed the DD13. This design integration helps to improve performance and reliability by reducing the number of joints and potential leak points. When the EGR cooler and the coolant collector are integrated into a single component, it simplifies the packaging, can enhance thermal efficiency, and contributes to reduced weight, which is beneficial for overall engine performance.

In the context of the DD15 and DD16 engines, while they also incorporate advanced technologies for emissions control and cooling, their designs differ in how the EGR cooler and coolant collector are constructed. The unique single-piece design of the DD13 makes it distinctive among the options provided.