• Oct 21, 2008
GM's new 4.5L Duramax diesel engine promises a 25% increase in fuel economy while providing 310 hp and 525 lb-ft. The new oil-burning powerplant also needs to pass 50 state emissions while providing the efficiency customers are demanding. GM has already provided some details of the Duramax 4.5L, including that the new diesel is roughly the same size as the General's compact small block V8, which means it can fit in more than just trucks and SUVs. The 4.5-liter also reduces the parts count with integrated aluminum cylinder head exhaust manifolds and an integral cam cover intake manifold. GM talked to Automotive News about new features of the lower half of the 4.5L Duramax, and they're just as extensive as the top.

[Source: Automotive News subs req'd]

Diesels run a higher compression ratio than gasoline engines, so components like crankshafts are built heftier to better-handle the enormous pressures of every day use. GM wants to keep the weight of the 4.5L down, though, because a heavy engine leads to heavier mounts, struts and brakes, which adds tonnage to the truck and saps away performance. To accomplish this, engineers started by casting the crank journals into the engine block, which reduces weight and lowers costs while also adding strength and precision. Because the sides of the bearing journals aren't cast into the wall of the cylinder block, the new crank journal design also improves circulation of air between cylinder banks. Better air flow means reduced pumping losses, which improves efficiency. GM has not used this process before, and may build the design into future gasoline engines.

Other noteworthy features of the 4.5L Duramax include a hollow balance shaft that transfers noise to the rear of the engine and into the thick transmission housing, which mutes engine noise. An aluminum upper oil pan that mounts between the engine block and the lower oil pan also stiffens the engine block by 30%, reducing vibration.The 4.5L Duramax diesel is scheduled to see production in fall of 2009 in the Chevy Silverado and GMC Sierra.


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  • 26 Comments
      • 6 Years Ago
      Looks to me like two bolt mains, three instead of five, on a V8? Durability not.
      Who designed this? Oldsmobile?
        • 6 Years Ago
        if you look at the picture you can clearly see the caps are numbered and they go from 2-4 which means it does have 5 main bearings. there are plenty of two bolt main diesel engines out there. in fact, most HD highway truck engines are 2 bolt mains. as for your cheap shot at olds i don't think that is a fair comment. when everyone else was sitting around biting their fingernails trying to figure out how to get more mileage out of thier gas sucking small blocks olds had the grapefruits to actually do something. yes, it didn't work all that well and there were major issues but they tried, and to even suggest a gas engine could be modified to operate on diesel takes some hubris. you at least need to give them that.
        • 6 Years Ago
        I am no fan of GM by any means. I have always been a ford guy even though my dad was a GM guy.

        All 4/6/8 bolt mains do is keep the main caps from walking. If your main caps walk, you will spin main bearings.

        2 Bolt mains can be just as effective if they are set up right.

        Take a 2 bolt 302 for example. Main cap walk can be an issue in high horsepower apps. with the factory main cap bolts but if you upgrade to arp main studs which can be torqued down to a much higher ft/lb main cap walk is eliminated. This is according to Muscle Mustangs and Fast Fords.

        So there you have it. 2 bolt main does not mean unreliable. It just depends.
      • 6 Years Ago
      Here's to hoping that GM can produce this engine at a reasonable premium over a gas engine($2000 perhaps)and be wise enough to offer it in all models of their full size truck/van fleet. If it is ultra reliable and can get 20 to 25 percent better fuel economy than a comparable gas engine they will most definitely have a winner. If it ends up under the hood of enough of thier trucks, it could help them in meeting future CAFE standards.
      • 6 Years Ago
      @ miles

      The 6L80 may not be able to, but I'm pretty sure the 6L90 is fine for that. IIRC, the 6L80 is rated to about 450ft.lbs.
      • 6 Years Ago
      look at all the experts in here!
      "2 bolt mains? what an underengineered POS! if it doesnt have the feature set of the supercharged 572BB i dropped into my new ZR1, then it sucks!"
      really people, if you dont know what your talking about, dont worry about posting a comment.

      BTW, the olds 350cu in diesel was a clean sheet design with the goal of having the same dimensions of a chevy small block. no, it was not a 350 with diesel new heads like everyone wants to think. the only thing they share in common are bore and stroke. and the connecting rods and pistons are even different sizes at that. dont believe me? look it up.
      • 6 Years Ago
      Cadillac may get a version of it?
        • 6 Years Ago
        That's what they say. May appear in the CTS. Here's hoping that they slap it in the Pontiac G8 (Holden Commodore) as well.
        • 6 Years Ago
        See, there's not a single diesel sedan out there that is made by an American company. They do not show any real desire to build it.

        GM already has a fuel efficient engine, Volt's, so they'll probably come out with a Caddy that is electric rather than oil burning.

        I believe Ford also has to plans for diesels in sedans and i believe you best bet for an affordable diesel is Honda Accord, i believe it should be in USA either in 2009 or 2010.
      • 6 Years Ago
      V6 diesel? This engine is ready for European market. It does produced 250hp and 420ft.lbs of torque. Made by VM motori in Italia. This engine has been shown in Geneva motor show in 2007.

      http://www.moteurnature.com/zvisu/2007/news13/vmmotori2_big.jpg
        • 6 Years Ago
        VM motors is owned 50% by gm and supplied the engine for the Jeep Liberty although before they bought
        the share. The engine was nothing to take note of.
      • 6 Years Ago
      two bolt main diesel - interesting to say the least.
      • 6 Years Ago
      Let me fix my previous. The HD version of the 6L80 handles up to 520ft.lbs. 6L90 should be a perfect fit for it.
      • 6 Years Ago
      This engine could easily ramp up to more HP/TQ. If it were in a Cadillac, they could easily tune it to 360HP.

      Cannot wait for this engine. They should also lop off 2 cylinders for a vortec V6 Duramaxx.
      • 6 Years Ago
      Would somebody explain the second paragraph. First it states that the crank journals are cast into the engine block and then immediately states "the sides of the bearing journals aren't cast into the wall of the cylinder block". The pic is not very enlightening regarding these seemingly contradictory statements.
        • 6 Years Ago
        MBM,

        In the picture you can see how the crank bearing caps are clear of the surrounding block skirting. Since the block does not have a cross-web at each bearing journal connecting the journal to the raised (in the picture) skirting, I think they are then saying the "journals aren't cast into the wall of the cylinder block."

        Peering at the picture more closely it appears as if the meat surrounding the bearing journal is rather "floating" in space between the cylinder block walls. I don't know how much turbulence is in there or how much aerodynamic pumping losses can be reduced inside the crankcase but sounds like they at least think they found something.
      • 6 Years Ago
      This is the engine I've been waiting for. Put it in half ton Pickups and the Tahoe/Suburban and I'll be ordering a few for my business.

      On a side note GM, please make sure this engine is available in stripped out work trucks and SUVs, unlike the Hybrid. I would love this engine in a Tahoe/Suburban, but I don't need, nor want, to pay $60,000+ for it because I can only get it as a package with every interior amenity.

      A simple model with this engine, 4x4, G80 rear, tow package, and basic LS interior (cloth) for less than $45,000 would be perfect.
      • 6 Years Ago
      GM woke up about 3 years ago and is now getting ready to kick-ass, when the economy gets better and if they don't run out of money.
        • 6 Years Ago
        Here's a dream, based on current rumor-milling: GM gets Jeep from Cerberus, throws the 4.5 Duramax in it with a 6 speed, and I can get great mileage all the way to, over, and beyond the nearest mountain range!


        Here's to dreaming...
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