5 Things: The New 6.6L Duramax Diesel Engine

Feb. 24, 2017 By Tim Healey

GM is adding a new 6.6-liter Duramax turbocharged diesel to the GMC Sierra HD and Chevrolet Silverado HD lineup this year. In fact, we just drove the Sierra HD Denali, which you can read more about here. The new Duramax has 90 percent new parts in spite of having the same bore and stroke as its predecessor. Hereís a closer look at five cool things that make this new turbo-diesel engine different from the previous generation.

Intake
Chevy actually has a patent pending on the new air intake system. Thatís because this air-intake system uses a functional hood scoop to drive cooler, drier air to the engine. The cooler air helps keep engine temperatures down, especially when the engine is under heavy load (such as when climbing a grade while towing). Chevy says reducing the temps helps to maximize power in the new Duramax.

Cast-Iron Foundation
In an effort to bolster strength, the engine has a cast-iron foundation with five iron main bearings and induction-hardened cylinder walls. Other design elements meant to bolster strength include a deep-skirt design and four-bolt main caps that are cross-bolted, a die-cast aluminum lower crankcase, larger-diameter connecting-rod journals and a new, stronger crankshaft.

Lightweight Cylinder Heads
Strength is great but not as much when it comes at the expense of added weight, so GM has given its new Duramax aluminum cylinder heads. It hasnít sacrificed strength, however, as evidenced by the six head bolts per cylinder, and the new double-layer water core construction is designed to offer great strength with enhanced coolant flow control to keep engine temps down.

Oil Separation
A Venturi Jet Drain Oil Separator will be used as part of a totally sealed system thatís meant to control oil flow under full load. It takes the fine mist of oil from the blow-by gas and uses some of the boosted air from the turbo to pump the collected oil back to the oil sump for reuse. This prevents oil from carrying over into the cylinders during combustion.

EGR
The Duramaxís EGR (exhaust-gas recirculation) system is actually a cooled system that Chevrolet says increases the engine performance and reduces emissions by taking some of the exhaust gas and bringing it back to the intake to mix with the fresh incoming air, thus lowering combustion temps and reducing the formation of nitrous oxides in the emissions. While EGR systems are par for the course, what makes this one unique is that it uses a heat exchanger to cool some of the exhaust gases Ė and a bypass allows for non-cooled gas to be fed back into the intake when the engine needs to warm up to prime operating temps quickly.

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