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Family/variant bore size and valve float


#1

I have a question regarding the relation between bore size and the valve float. Why changing the engine’s variant bore size is not affecting the valve float, while changing the family bore size is? For example we have three engines:

Family 1, 80mm x 80mm (bore x stroke)

  • variant A, 80mm x 80mm (bore x stroke)
  • variant B, 70mm x 80mm (bore x stroke)

Family 2, 70mm x 80mm (bore x stroke)

  • variant A, 70mm x 80mm (bore x stroke)

I understand why 1A would have more valve float compared to 2A. Larger valves etc. But why 1B has the same valve float as 1A? As I understand/imagine 1B should have the same valve float parameters as 2A, as the valves, springs, rocker arms would/should be identical in both 2A and 1B (might be not true for pushrod engines). The cylinders would have the same shape, but they would be more spread out, so the camshaft(s) would be longer, and maybe a bit thicker (to increase stiffness due to increased length), but this shouldn’t affect valve float.

Am I missing something? Or is this is a bug?


#2

basically:
both variants of family 1 share the same head and thus the same valvetrain

the only change to make variant B’s bore smaller than variant A’s one is thicker cylinder liners


#3

Have you seen how close to the cylinder edge some heads have the valves?
A high powered engine cannot reduce the bore that much without reducing valve size.


#4

If that would be the case I would also expect (as @RobtheFiend) the valves not fitting in the cylinder for larger variant (hitting cylinder liner), or larger variant’s valves to be unnecessarily small, blocking the air flow and inefficient.

But yes, that could be a plausible explanation in the Automation Game’s world: engine heads are designed to fit the smallest possible variant of the whole engine’s family.


#5

either that or the liners could have some clearance “holes” or “indents” to make space for valves

could imagine the same on the bottom end for conrod clearance.


#6

Are you guessing or maybe you know such solution is/was being used by some manufacturer? It would make a shape of the combustion chamber very weird and probably inefficient (combustion expanding in those “holes”/“indents” wouldn’t be able to exercise any work on the cylinder directly).


#7

just some guesswork lol