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Old 06-05-2012, 01:44 AM
Acavet Acavet is offline
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Default What CC size motor equals what hp?

In the old days small engines where rated by their horse power. Most mini-bikes and go karts had 3-5 hp engines. Some of the larger karts and bikes had 8-10 hp. Today most of the engine manufactures are not giving the HP rating of the motors just the size of the motors in CC's.

Can anyone provide a breakdown of what CC motor equals approximately what horse power?

Thanks.
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Old 06-05-2012, 01:46 AM
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Originally Posted by Acavet View Post
In the old days small engines where rated by their horse power. Most mini-bikes and go karts had 3-5 hp engines. Some of the larger karts and bikes had 8-10 hp. Today most of the engine manufactures are not giving the HP rating of the motors just the size of the motors in CC's.

Can anyone provide a breakdown of what CC motor equals approximately what horse power?

Thanks.
Unfortunately, there is no equation for converting the two. There is no relation that you can use to work it out.

Do a bit of googling, and you will see that it is impossible.

I also used to think that there was some conversion, but there isn't
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Old 06-05-2012, 01:49 AM
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Here is an approximate cc to horsepower chart for small engines. This chart ONLY gives an IDEA of how much horsepower CAN BE achieved by a stock engine of that CC size. There are too many variables, such as carb size, muffler flow, timing, valve duration.

123 cc = 4 hp
179 cc = 5 hp
208 cc = 5.5 to 6 hp
277 cc = 7 to 8 hp
291cc = 9hp
305 cc = 9 to 10 hp
342 cc = 11 to 12 hp
357 cc = 13 hp
420 cc = 13-15 hp

The formula that is below only applies to the small newer normally aspirated (carbureted) 4 cycle engines. The ratios change slightly worse with altitude and slightly better with fuel injection and tuning.

Typical new carbureted small engine:
1 x HP per each 25 cc
Fuel injected:
1 x HP per each 22 cc
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Old 06-05-2012, 04:45 AM
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that is about right but gives u a very wide range or just lawn mower engines

my 600cc bike engine is pushing 140hp

my 800cc honda water pump pushes 24hp
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Old 06-05-2012, 05:12 AM
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If you have some torque figures you can work it out from that.
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Old 06-06-2012, 05:29 AM
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If you know the torque you can calculate your HP. Torque (in ft/lbs) times rpm. Divide by 5252. This is your horsepower.
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Old 06-06-2012, 06:01 AM
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If you know the torque you can calculate your HP. Torque (in ft/lbs) times rpm. Divide by 5252. This is your horsepower.
Why divide by 5252? Seems a tad random haha. Thats not the conversion as far as i know. In saying that I work in metric so I dunno
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Old 06-06-2012, 07:15 AM
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I have a 9hp honda engine, which is 270cc. As people said before, it's hard to decide how much hp an engine has if you know the cc.
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Old 06-06-2012, 07:15 AM
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Yeah that calculation is correct. Have a look at this for why.
And read this. A few examples of why displacement does not always relate to HP.
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