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Displacement calculation/rounding questions


#1

Since the newest UE4 open beta update, I’ve been trying to rebuild engines. I can’t seem to get the bore x stroke numbers to match up with what the CID or LD should be. A 4.00" X 3.75" V8 engine in the game comes up as 376.1 CI when it should be 377. A 4.25" X 3.75" engine comes up as 425.0 instead of 425.6. Changing to metric seems to make it worse, a 101.6x95.3 engine (as best I can tell since we don’t get decimals past 100) comes up as 374.2ci when it should be slightly larger than the 4"x3.75" engine. and the 426 shows up as 421.8…

Am I missing some rounding here? I’m using the normal displacement calculation (bore/2)^2 * stroke * PI * cyl count.

Also, is there a way we can type in bore/stroke numbers instead of using the slider?


#2

I suspect that 101.6 gets rounded to 102, since this is what I get

image

If I use numbers under 100 so they don’t get rounded, it seems to work properly.

As for your issue with measurements in inches, that’s because each increment is .1mm or .004 inches, which is smaller than the accuracy of the indicator. And since it’s the same exact slider with the same exact values as when the game is set in millimeters, you will often not be able to get exactly to the measurement you want.

Here is how close I could get with the first set of numbers you gave:
image

4 inches gives you 101.6 millimeters, which is possible with the slider in millimeters, however 3.75 inches gives you 95.25 millimeters, so you have to use 95.2 or 95.3.


#3

Thanks, I suppose I’ll do everything in metric then, though I do wish it would give us a full 4 digits. Guessing or counting the tenths over 100mm is a bit annoying.


#4

The additional digit not showing when going beyond 100mm definitely is a bug :slight_smile: we’ll have a look tomorrow.


#5

Awesome. Thanks!