New aluminum cylinder heads replace cast iron to save weight. They feature dual water jackets for cooling and a six-bolt attachment pattern for extra strength. Note the asymmetrical sizes and layouts of the intake (larger) and exhaust (smaller) ports.
Why? The arrangement dramatically shortens the distance between the exhaust and turbo, improving turbo response while protecting nearby powertrain components, like the fuel pump and alternator, from excessive heat. Higher turbo outlet temps also provide extra heat to downstream emissions devices to improve pollution-scrubbing performance sooner while emission catalysts (used to break down harmful pollutants) are warming up.
“Total exhaust volume and surface area of this configuration is about half that of the previous engine,” Gryglak said. “At the same time, we’ve been able to significantly improve the throttle feel of the truck.”