ClearTech SCR engines drop emissions, not performance. As an industry leader in engine development, Mack® remains at the forefront of engine development, incorporating selective catalytic reduction (SCR) technology into our MP® engine platform. The Mack ClearTech™ SCR System—the first to be certified by the EPA—creates clean-running and fuel-efficient engines that boast near-zero emissions to meet strict EPA standards. Used successfully in hundreds of thousands of trucks around the world, SCR is the proven, reliable approach. Where the ClearTech system fits When incorporating SCR technology into the MP Engine Series, we were careful to configure the system without impacting normal daily operations. The compact design allows for easy integration without altering the cab or chassis. Diesel Exhaust Fluid (DEF) Tank On the driver side of the truck, the Diesel Exhaust Fluid (DEF) tank is tucked between the cab steps and the fuel tank. This placement is convenient for refilling operations. SCR Catalyst The passenger side of the truck houses the catalytic conversion chamber that sits behind the Mack Cap Diesel Particulate Filter (DPF), under the steps. It is positioned just behind the cab and along the frame rail. Cleaning up the streets We seamlessly incorporated a DPF into the exhaust system of all our trucks with a technically savvy solution to meet emissions requirements. The catalyzed design of our DPF system allows the use of passive exhaust heat to oxydize the collected soot, virtually eliminating the need of an active (diesel fuel supported) DPF regeneration, in all highway and most vocational applications. How the ClearTech SCR system works The Mack ClearTech SCR System works by directly injecting DEF into the engine’s hot exhaust gas stream to reduce NOx emissions to a near zero amount. The injected DEF vaporizes immediately in the exhaust stream and, through elegant chemistry and a catalytic reaction, reduces NOx into harmless nitrogen (N2) and simple water vapor (H2O). The amount of DEF injected into the exhaust is monitored by NOx sensors and regulated by the Aftertreatment Control Module (ACM).