Under its hood is GM’s revolutionary new dual-overhead cam 4.5-liter Duramax V8. The 4-valve engine was designed with 6 dozen fewer parts than a conventional diesel. Separate intake and exhaust manifolds have been eliminated and integrated directly into the engine. Airflow is reversed, so fresh air enters through the outer portion of the cylinder heads and exhaust gases are dumped inboard into a variable vane turbocharger and EGR cooler that sits in the valley of the 72-degree V8. Removing hardware and rearranging key components reduces the 4.5-L Duramax’s footprint compared to conventional V8 diesels with similar displacements, so the 4.5-L Duramax can fit in the same space as GM’s 6.2-L small-block gas V8.

GM officially says it expected the 4.5-L Duramax to deliver class-leading horsepower and torque, with ratings in excess of 310 horsepower and 520 pounds-feet of torque. It would also meet stringent 2010 light-duty emissions in all 50 states, using a diesel particulate filter to remove soot and urea selective catalytic reduction to scrub nitrogen oxide. Despite all of the restrictive emissions equipment, GM says this truck should average 25% better fuel economy that its gasser counterpart.

Even though it shares the Duramax name with the heavy-duty 6.6-liter V8 — which has been engineered and produced in partnership with Isuzu Motors — the new diesel was 100% designed by GM and will be built without Isuzu’s involvement.