Engine Displacement Logic?

[galaxy]

So check this one out. Someone called me out on my license plate (FLAT 315) about the cubic inches. When you convert it doing basic math, 5.2L does not come out to 315 cubic inches. 5.2L = 317.3.

BUT...every article, news blog, spec sheet, the OWNERS MANUAL, Ford, and on and on and on, list it as 315 c.i. I also even saw it listed at 5167 cubic centimeters.

5167 = 315 ≠ 5.2L

What's going on here? Is there a difference between doing basic math conversion and how they derive engine displacement?

 

[Weather Man]

Rounding.

 

[galaxy]

Aaaahhhh, you know what. I thought of that, but you made me think to work it the other direction. 315.3 = 5.16L...rounded to 5.2L

Case closed.

 

[tt335ci03cobra]

Yep, the 5.0’s from the 1960’s and later in 79-95 were 4.942’s (roughly) as well. 305ci is a 5.0, so technically the Chevy 305 is the real 5.0 or the era.

Rounding is very common. I’ve seen gratuitous rounding even by AMG, their “6.3” is anything but. That said, they used 6.3 instead of 6.208 ecause of historic reference. Same with the 5.0 with Ford. Plus 5.0 sounds better than 4.6, and 5.2 better than 5.1

My “5.3 big bore stroker” in my 03 cobra is really a 323ci, which is 5.298 iirc, 3.7b 3.78stroke.

 

[DSG2003Mach1]

you should see how bad ATVs and such can be about this, the Honda Rancher we have is called a 400 but it checks in around 340cc...