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It is common to find this kind of detailing and patterning on engine blocks and related parts. Older engine blocks display much more flatter and simple geometry and this kind of mold work must come with a considerable production cost. What is it's purpose?

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  • $\begingroup$ Strange that the water jacket should have so much reinforcement for its relatively low pressure . $\endgroup$ Mar 20 '18 at 3:58
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This pattern is to provide sufficient strength while minimising the mass of the block.

These "webs" are designed to prevent any vibration, if the block wall was made thin and the full length and width it would buckle or fail under the loads / stresses applied.

This design allows the wall to be thin in-between the webs so reducing the mass and helping to reduce the overall mass of the vehicle and help fuel consumption.

Also, you can see how the bolt holes or fixing points are re-inforced with extra material.

You mention the "extra work" necessary, but also consider the amount of material saved per block multiplied by the number of blocks produced...

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    $\begingroup$ Also worth noting that a lot of the "extra work" in production costs just requires you to create a working mold for that engine geometry. It's not like each individual piece would need to have those details machined in. $\endgroup$
    – JMac
    Mar 14 '18 at 12:12
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    $\begingroup$ Since these are probably made with sandcasting, a model is only made once, the casting mould is made out of that a bit like a sandcastle, then this can be duplicated over and over again and complexity has really no meaningful impact (if its not certain kind of complexity) on price. In fact having a more uniform wall thickness probably means better controlled casting process thus less failed casts. $\endgroup$
    – joojaa
    Mar 14 '18 at 15:17
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As mentioned in other answers these patterns are structural stiffeners to give strength to a lighter engine block.

But they also have the task of distributing stresses due to internal vibrations of moving parts and concentrated stress of attached accessories such as exhaust manifold.

That is a big help in increasing longevity of the entire engine assembly, reducing fatigue cracks in the long run, and bringing the maintenance cost down.

These fins are also designed to make the engine run quieter and smoother.

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  • $\begingroup$ most of the "cracks" I have seen in engine blocks (and seen more than a few...) tends to be due to parts like con-rods making an exit... $\endgroup$
    – Solar Mike
    Mar 14 '18 at 14:59
  • $\begingroup$ Since the advance of computer simulation and FEM analysis they have improved the design of engines and studied the vibration if engines including the knocking of attached accessories and brackets acting as base for filters and what not. That is the reason we see advanced performance at lower weights. Early stage fatigue cracks are detectable only by ultrasound probes. They do this in aviation more because of critical mission of engines. $\endgroup$
    – kamran
    Mar 14 '18 at 16:32
  • $\begingroup$ they do crack testing on a lot more than just engines, not only that they also uphold a MUCH better standard of maintenance... including better qualified mechanics / engineers / fitters... $\endgroup$
    – Solar Mike
    Mar 14 '18 at 16:53
  • $\begingroup$ @kamran Although, according to FEM models old wrought iron Wärtsilä designs break within 10 cylces, i am told, though in reality there are some 25 year old specimen of those in existence. $\endgroup$
    – joojaa
    Mar 14 '18 at 18:31
  • $\begingroup$ @joojaa, Finite Element and numerical simulation methods are very reliable, but it depends on how complex and sophisticated each element is set up! is it set with right flexibility and thermal properties. Is the resolution of elements fine enough to adequately represent the actual part. e.g.; in simulation of flow of gases do they go by streamlines or by unsteady Euler equations. In solids do we consider elements capable of propagating stress shock? They simulate with high degree of precision the force and impact of hurricanes or explosions, but it depends on how careful the models set up. $\endgroup$
    – kamran
    Mar 14 '18 at 22:21
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There are two closely related reasons.

The first is that in terms of pure geometry webs tend to be more efficient in terms of strength and stiffness to weight ratios compared to a solid block of similar dimensions. You also see this a lot in fabricated and pressed structures.

The second is that in castings it is generally desirable to keep section thickness as consistent as possible and within a certain range to reduce the potential for casting defects related to shrinkage. It is fairly rare to see quite such intricate webbing in an engine block as it somewhat complicates mould design and in many cases an over engineered approach is preferred in terms of stiffness and vibration damping and where weight is critical it tends to be easier to change materials rather than produce highly optimised castings.

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I have never seen that, very interesting. I expect the webs are stiffeners as mentioned. But I expect thin flat sheet of metal will cover the surface shown to enclose a water jacket. There are not enough fins for air cooling. so there must be a water jacket.Is it iron or aluminum ? It looks like aluminum but I don't see steel/iron cylinder liners.

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    $\begingroup$ Downvoted for being primarily speculation (although not necessarily incorrect) $\endgroup$ Mar 14 '18 at 23:01

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