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Discussion Starter · #1 ·
Has anyone ever done any testing to see what the drop in efficiency is as engine cc's goes up?

For example, if a motor is at a certain cc and makes "x" amount of hp per cc (or CI), and you increase the size of the engine, going to a larger displacement, what would you expect the hp output to be if the engines are in virtually the same state of tune?

Reason I am asking, I've got my little Honda 250R that currently is at 16.35 cubic inches (268cc's) and putting out 56.4 hp. That makes the HP per Cubic Inch right at 3.45 hp/ci. What could I expect that number to be if I increased my displacement to say a 310cc engine, and then say a 330cc engine (and so on.... 350cc, 370cc, 431cc etc.)

I have been contemplating this for a bit and am rather curious about it.

As engine size goes up, is it to be expected that efficiency would drop?

Thanks.
 

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Discussion Starter · #7 ·
So what you all are saying is that there are really too many factors to really put a good number to how much the efficiency of a motor goes down as displacement goes up.

Perhaps a better topic might be is "what is the most efficient engine configuration?" (ie - square, over-square, under-square, etc....)

My take on it is, in fact, that efficiency does go down as displacment goes up. It's just hard to say by how much.

Am I correct in my statement?

Thanks.
 
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