So I think we all can agree that trying to equate cc's to hp is a PITA and somewhat a hard concept to grasp. I was looking on-line for some sort of conversion tool and came across several formulas that did not make sense to me. They seemed to place the hp ratings much higher for a given cc displacement if you followed the prescribed formula. What I noticed is that they seemed to double the HP rating. Anyway I played around with it a bit and came up with this - it provides a fairly accurate cc to hp conversion without a lot of headaches:
cc displacement (cubic centimeter size of engine) divided by 16 divided by 2
I've tested it out and it seems to be pretty accurate. For example: A Honda 9 HP engine has a displacement of 270 cc's. So... 270 divided by 16 = 16.875 divided by 2 = 8.4375 which is close to the 8.5 HP rating that this engine has historically been rated at in HP.
Another example: A Honda 11 HP engine has a displacement of 340 cc's. 340 divided by 16 = 21.25 divided by 2 = 10.625 which again is very close to the 10.5 HP rating Honda has rated this engine at in HP.
The middle number (16) may have to be increased or decreased based on the size of the engine to get a more accurate estimate.
If for nothing else, it gets you in the ballpark.... Try it out!
This message was modified Oct 6, 2011 by FrankMA
Toro Wheel Horse 522xi GT, Honda HS928TA, Honda HS621AS, Honda HS520A, Toro CCR3000 (work in progress), Honda HS624WA (sold 08/23/2010), Stihl BR550 Backpack Blower, Stihl MS250, McCulloch MS1635, Honda EM6500SX Generator