Why is this man smiling? Because he's Charlie Freese, the man behind the new 4.5L Duramax engine. The 4.5L meets the world's strictest emissions requirements and still manages to produce 310 hp and 520 lb-ft of torque.
We recently attended a seminar on the new 4.5L LMK Duramax that will be making an appearance in light-duty trucks for 2010. This potent mill will not only have at least 310 hp and 520 lb-ft of torque (final figures have yet to be released), but it makes these ratings while meeting stricter emissions regulations. How? With a lot of technology. To get the lowdown on this new tech-heavy engine, we're going to have a Q&A session with our new friend Charlie Freese. Who is Charlie? Well, he's one of the guys who spearheaded the 4.5L buildup, as well as the Executive Director of Diesel Engineering over at GM.
Diesel Power:
OK, first comes first. We're sure most people are wondering about the switched intake and exhaust arrangement on this engine. Why did you choose to mount the turbo in the middle and have the intakes on either side, rather than just building an engine the "traditional" way?
Charlie Freese:
The inboard exhaust configuration is a unique design characteristic. When we started this clean-sheet engine, it was important to think through the design imperatives. As you mentioned, the engine had to deliver high power and torque density while meeting the world's most stringent emissions standards.
This is the type of vehicle that will receive the new 4.5L engine. We're expecting 14-second quarter-mile times and 20+ mpg right off dealer lots.
Efficiency and capability are key reasons to select diesel powertrains, and exceptional durability is the price of entry for any engine that will carry the Duramax badge. Cost, packaging, and mass are all necessary constraints that determine if the engine can work in a vehicle and be successful in the marketplace. Inboard exhaust supports all these requirements. It helps to take a deeper look at how the exhaust arrangement interacts with the design imperatives.
Let's start with emissions-2010 Tier-2 and LEV2 emission standards are challenging. Exhaust aftertreatment gains additional importance. We will use particulate and NOx aftertreatment, and these devices work best when quickly heated to operating temperatures. Exhaust energy warms aftertreatment components, but exhaust heat represents fuel energy that didn't make power. We want to minimize thermal losses and warm the aftertreatment system efficiently. In Europe, we closely couple aftertreatment hardware to exhaust manifolds. European 4-cylinder engines simplify this situation because exhaust exits from one side of the engine. Things get trickier for V-engines, so using traditional outboard exhaust requires a compromise. Either a separate aftertreatment system would be needed for each bank, or the hardware must be located remotely. That could mean 6 feet away from the engine, so inboard exhaust provides a better solution. By collecting exhaust inboard, we can position the turbocharger and oxidation catalyst in the valley and avoid extra plumbing.
Globally, GM makes everything from a 1.3L four-cylinder diesel to the 6.6L Duramax. Look for the 4.5L and the 6.6L here in the U.S. Word is the 250hp 2.9L V-6 diesel will be debuting in a Cadillac in 2009. | 
The new 4.5L Duramax will be able to fit anywhere that a small-block Chevy is located, which means swaps into other vehicles (Corvettes?) may be in the engine's future. | 
The new 4.5L is built at a 72 angle instead of the usual 90, making for a much tighter package. |
Some traditional designs valley-mount turbochargers, requiring crossover pipes to collect exhaust from outboard manifolds, so we wanted to avoid this if possible. Inboard exhaust removes the crossover pipes adjoining the two banks, but the 4.5L also eliminates exhaust manifolds. The turbocharger connects to the heads. The 4.5L design eliminated more than six dozen engine parts. That means less mass, better reliability, and less cost. Now let's discuss performance. Air restrictions and heat losses rob an engine of performance. Keeping short exhaust passages between the turbine and the cylinder heads reduced both inefficiencies. If we used outboard exhaust, long pipes would be required to carry exhaust gas into the valley where the turbo sits. These pipes increase backpressure. Noise is another important consideration. More pipes and manifolds mean more surface area, and these surfaces are where thermal energy and noise would be radiated into the engine compartment. The 4.5L's inboard exhaust arrangement avoids these pitfalls.
We can't leave out durability, which is synonymous with the Duramax brand. Losses mean inefficiency and must be overcome by higher fuel consumption for the same power density. Reduced fuel consumption helps lower thermal stress in the combustion chamber components and minimizes cranktrain and structural loads. These are good things for engine durability.