CC's and horsepower

notjustair

Well-known Member
On small engines, are CC's and horsepower always related in the same ratio? I know on large engines they are not but I wasn't sure about mower size engines.

I have one of those 4x4 Japanese mini pickups that I use every day on the farm. It has a two cylinder water cooled 547 CC engine and a four speed transmission. It will run 60 miles an hour down the road and haul 1000 pounds in the back. It seems very strong for such a little engine (and I think it is pretty high geared). My big ZTR has an 18 horse twin Briggs which is just shy of 700 CC's. So is the little pickup equivalent to 16 or so horsepower? Everything on it is written in Japanese but I'm not sure it would say anyway. Just curious.
 
There is no correlation between displacement and horsepower. You can have a large displacement engine and a small displacement engine that produce the exact same amount of horsepower. You can also have 10 engines with identical displacement that produce 10 differing amounts of horsepower.

As an example, take the amazing Chevrolet 283 cubic inch V8 engine from the 50's and 60's. You could order a car with this engine producing 185 HP, 195 HP, 210 HP, 240 HP, 260 HP, 283 HP and 315 HP. The displacement remained the same but the compression ratio, camshaft profile, valve sizes and type of carb/injection is what made the difference in HP ratings.
 
Typical "small gas engines" used for mowers like Briggs and Kohler run at a maximum speed of 3000-3600 rpm while the engine in your mini truck probably revs to double that. Doubling the engine speed with the same torque output will double the power. If you are comparing mower engine to mower engine this speed variable goes away and the size-to-power will be more proportional. However, you still have variables that will effect the ratio, such as overhead valves vs flathead.
 

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