Charge air cooling is an important topic especially with higher horsepower B series engines. Often people will look at a pickup truck rating and question why charge air cooling is needed when pickup engines were not equipped with charge air coolers even at 175+hp. The answer lies in an engine's expected duty cycle and design life.
Charge air cooling not only helps deliver a denser charge as a part of the recipe for higher engine output, but can also increase an engine's durability. Cooler intake air translates into cooler combustion temperatures and ultimately cooler running internal engine components. With aluminum piston engines like the B Series Cummins, higher pistons temperatures reduce the aluminum's ability to resist fatigue (cracks) since aluminum's fatigue strength decreases with higher temperatures. A way of thinking about this is that every engine cycle consumes a small amount of an aluminum piston's life. Therefore, as temperatures go up, the amount of life consumed during a given cycle increases, and the piston's overall life decreases at a faster rate than if it were operated at a lower temperature.
In a light duty application, the time spent at high loads and hence high temperature is assumed to be a low percentage of the vehicle's total life. Therefore, it is possible for a component to achieve the desired design life without charge air cooling even if internal temperatures are high. In an off-road application, duty cycles are typically higher when compared to automotive applications. In order to provide acceptable engine life under more demanding conditions, internal temperatures must therefore be reduced.
If there is any doubt regarding if charge air cooling is required for your project, a discussion with a Cummins application engineer is recommended. However, it is my general rule of thumb that for 140 PTO horsepower and above that, charge air cooling should be used when long life and durability is desired.