Laminar, you are exactly correct. The 2.3 EcoBoost and the 2.3 Duratec are virtually identical short blocks. The reason that the Duratec, as well as the "turbo Duratec" EcoBoost almost always spin rod #3 is that the oil galleys are incorrectly designed and tend not to properly lubricate the entire engine.
There exists more documentation than one could reasonably be expected to read on the common failures, but that's something you'll have to google yourself. The old Duratec 23 had the interesting quality that it would either blow by 100k miles, or run forever. The EcoBoost also has the same reputation for failure, but due to substantially increased load and increased need for lubrication, failures tend to be more common and earlier. Of course, there is likely some confirmation bias there; a huge portion of my research on the engine has been repair information. Invariably forum posts regarding repair of the engine will begin by stating that the cause of failure is among the two common failure modes of the design; spun bearing due to oil starvation or cracked block due to questionable casting quality.
An interesting note is that the Duratec 25 largely avoids the major issues of the 2.3. The block is almost identical but taller and therefore must be a separate casting. The casting itself is revised to address the oil galley issue and does so very well. There is increased webbing in the block where there is a known week point. This doesn't completely negate the fault, but most people never have issues with blocks splitting on the 2.5 unless they're souping it up. The 2.5 also has a longer stroke and makes more torque at lower RPM, runs a little cooler, and because of the improved torque curve, makes slightly better real-world fuel economy. There are still weak points but they're not catastrophic. I have no idea why Ford didn't develop the stronger 2.5 as their primary EcoBoost option; it would cost the same, save a tiny bit of fuel, and make more power.
There exists more documentation than one could reasonably be expected to read on the common failures, but that's something you'll have to google yourself. The old Duratec 23 had the interesting quality that it would either blow by 100k miles, or run forever. The EcoBoost also has the same reputation for failure, but due to substantially increased load and increased need for lubrication, failures tend to be more common and earlier. Of course, there is likely some confirmation bias there; a huge portion of my research on the engine has been repair information. Invariably forum posts regarding repair of the engine will begin by stating that the cause of failure is among the two common failure modes of the design; spun bearing due to oil starvation or cracked block due to questionable casting quality.
An interesting note is that the Duratec 25 largely avoids the major issues of the 2.3. The block is almost identical but taller and therefore must be a separate casting. The casting itself is revised to address the oil galley issue and does so very well. There is increased webbing in the block where there is a known week point. This doesn't completely negate the fault, but most people never have issues with blocks splitting on the 2.5 unless they're souping it up. The 2.5 also has a longer stroke and makes more torque at lower RPM, runs a little cooler, and because of the improved torque curve, makes slightly better real-world fuel economy. There are still weak points but they're not catastrophic. I have no idea why Ford didn't develop the stronger 2.5 as their primary EcoBoost option; it would cost the same, save a tiny bit of fuel, and make more power.
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