What process delivers improved fuel economy in modern diesel engines?

The process that significantly contributes to improved fuel economy in modern diesel engines is Selective Catalytic Reduction (SCR). This technology utilizes a catalytic converter that reduces nitrogen oxides (NOx) emissions by injecting a urea-based solution into the exhaust stream. By transforming harmful emissions into nitrogen and water, SCR helps engines operate more efficiently, allowing for a more complete combustion process. This more efficient combustion means fewer fuel losses and improved fuel economy.

In addition to the emissions benefit, SCR enables diesel engines to operate at higher compression ratios and leaner air-fuel mixtures, which further enhances fuel efficiency. As a result, engines can produce more power using less fuel, directly contributing to better fuel economy.

Other processes, while also vital for emissions control or engine performance, do not primarily target fuel efficiency in the same way that SCR does. For instance, diesel particulate filter regeneration focuses on maintaining the filter's effectiveness at trapping soot, while exhaust gas recirculation recycles exhaust gases to reduce NOx emissions, and turbocharging increases power and efficiency but does not target emissions.