Downsizing was accomplished by the new diesel's lack of intake and exhaust manifolds. The aluminum cylinder heads' exhaust ports face inward, enabling exhaust gas pressure to directly feed the variable-geometry turbocharger, exhaust gas recirculation cooler and oxidation catalyst, all neatly situated within the engine valley. The intake manifold, typically mounted atop the cylinder heads, was eliminated by routing the turbo-pressurized intake air through the camshaft covers, then internally to the intake ports. A large portion of the engine's efficiency is attributed to the short travel distance for intake and exhaust gases.
The engine block consists of compacted graphite iron, said to be stronger than aluminum yet lighter than cast iron. To further minimize engine width, the V-angle is narrowed to 72 degrees, as opposed to a standard right-angle V-8--inevitable vibration is compensated by a counterbalance shaft. The decrease in total mass, in conjunction with the use of a single turbocharger, makes this engine cheaper to build.
According to GM engineers, the new 4.5-liter powerplant is estimated to peak at 310 horsepower and 520 pound-feet of torque. Production is scheduled for GM's Tonawanda, New York, engine plant in late 2009. Additionally, since the 6.6-liter Duramax doesn't yet meet 2010 emissions, that engine will be redesigned, and it's a possibility that the design and production features of the 4.5 may be applied to its big brother.