What HP is 318cc?

Horse power (HP) cannot be directly converted from the cubic capacity of the engine,

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The formula that works best only applies to the small newer normally aspirated (carburetor) 4 cycle engines. The ratiOS change slightly worse with altitude and slightly better with fuel injection and tuning. Most American mowers and the newer 4 cycle outboard motors fit into one of these two formulas:

Typical new carbureted engine well tuned:

1 x HP per each 25 cc

Fuel injected:

1 x HP per each 22 cc

Notes:

• Most engines are tuned down to a lower HP for better engine life.
• It is common for the same cc engine to be built in 3 different HP versions with the highest rated being the maximized HP per cc version. That is how you see price and HP changes on the same cc engine made by the same company.
• Some of the newest (2008 and newer) engines from Japan perform slightly better.
• A typical 150cc motor should equate to between 3.5 - 6 HP+ depending on tuning with 5 HP being the adv.
• The actual formula plots as a curve and not linear but does not apply to Max/High Performance engines like motorcycles.