# CC to HP



## [email protected] (Dec 12, 2013)

I'm in the market for a new machine,not used to CC...... What ever happened to HP
From what I read you divide CC by 2 then divide that answer by 2 = HP
Today a salesman told a certain machine 420CC was same as 10HP
When I calculate it, it comes out to 13HP, am I wrong on how to calculate.


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## cub cadet 3x (Nov 2, 2014)

[email protected] no your good in your conversion have a look here you'll see your good

Small Engine Cubic Centimetres (cc) to Horse Power Calculator 

i have a 420cc engine and was wondering the same what was the HP
http://www3.telus.net/shebang/engine_cc_to_hp_calculator.html


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## 94EG8 (Feb 13, 2014)

You can't directly equate CC to HP, it just doesn't work.


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## Normex (Feb 21, 2014)

[email protected] said:


> I'm in the market for a new machine,not used to CC...... What ever happened to HP
> From what I read you divide CC by 2 then divide that answer by 2 = HP
> Today a salesman told a certain machine 420CC was same as 10HP
> When I calculate it, it comes out to 13HP, am I wrong on how to calculate.


 +1 with cubcadet but with the same block size the engine manufacturers can vary the HP from 8hp to 13hp with practically the same engine as it all depends on the carb and timing of the engine in question and the output HP the snow blower actually needs. It is confusing a bit but it's all a question of economics for these manufacturers.


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## caddydaddy (Dec 10, 2014)

94EG8 said:


> You can't directly equate CC to HP, it just doesn't work.


Very true!

That calculator link that was posted is probably pretty close to what a small engine makes given the CCs.


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## Shryp (Jan 1, 2011)

The closest answer would be to look up Honda engines. They post CC and HP for most of their GX engines. You also have to remember that over head valve and side valve engines don't compare to each other at all.

As for the reason why, there was a lawsuit about 7 years ago or so from companies fudging their numbers. Now they just use the volume inside the engine.


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## Normex (Feb 21, 2014)

Shryp said:


> The closest answer would be to look up Honda engines. They post CC and HP for most of their GX engines. You also have to remember that over head valve and side valve engines don't compare to each other at all.
> 
> As for the reason why, there was a lawsuit about 7 years ago or so from companies fudging their numbers. Now they just use the volume inside the engine.


Shryp with Honda aside would you agree that some manufacturers use the same volume for different HP output depending on the need?
Tecumseh had 3 different HP outputs with the 358cc as far as I know.
Many thanks


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## suspicionofignorance2 (Jan 26, 2014)

I agree with 94eg8....The concept is no good...Flatheads, OHV, OHC...At what RPM...Etc...and no mention of Torque....the real measure...Wondering if the calculator would have been more accurate if it converted CC to torque..?


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## Coby7 (Nov 6, 2014)

You can convert cc to cubic inches and nothing else.


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## Coby7 (Nov 6, 2014)

420 cc would be a 25 cubic inch.


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## Coby7 (Nov 6, 2014)

Probably a 2.75" piston with a 3 inch stroke.


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## 94EG8 (Feb 13, 2014)

Normex said:


> +1 with cubcadet but with the same block size the engine manufacturers can vary the HP from 8hp to 13hp with practically the same engine as it all depends on the carb and timing of the engine in question and the output HP the snow blower actually needs.


I have actually seen Briggs & Stratton use an intake manifold gasket that blocked half the hole to reduce HP so they only needed one engine to cover the 15?hp - 22hp range for single cylinders.


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## Normex (Feb 21, 2014)

94EG8 said:


> I have actually seen Briggs & Stratton use an intake manifold gasket that blocked half the hole to reduce HP so they only needed one engine to cover the 15?hp - 22hp range for single cylinders.


 It's almost like what a shame but then most all small engine companies does the same in different manners.


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## ClaudeK (Jan 4, 2015)

Yup, even Honda. At least with GX390. Somehow there was 1132 (11hp) then 1332 (13hp) and when you look at the GX390 specs. it says 11.5hp. Go figure.


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## scrappy (Dec 7, 2014)

Perfect example of HP is Tecumseh HS5 compared to H5. Both are close to to 12 cubic inches. The small block has a shorter stroke larger bore compared to the big block with a long stroke small bore. Both are rated for the same Hp. 

The big block long stroke would have more torque at a lower RPM, better for snow blowers. The Short stroke small block would be better for high rpm's such as go carts and mini bikes..

Funny how both are rated for 5HP at 3600 rpm from the same manufacture.


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## sscotsman (Dec 8, 2010)

Im actually glad that horse power ratings are no longer being used..
because they were the most arbitrary and meaningless of measurements..

The only thing they were good for was comparing one engine to another,
in theory we would expect a 8hp engine to be slightly more powerful than a 7hp.
but..manufacturers could fudge the calculations! which probably often meant
it wasn't even a valid comparison anyway..

and..perhaps 200 years ago a 1hp steam engine was roughly equivalent to one actual horse..
but am I really supposed to believe that this:










Is the power equivalent of this?










I dont think so! 
(engine manufacturer is irrelevant..)

yes I know: "its not supposed to mean literal horses anymore"..
but thats my point..if it doesnt mean literal horses anymore, 
then what _does_ it mean? no one knows.. it means nothing..

so HP ratings are totally useless, on many levels..
at least cc and ft/lb measurements actually mean something real..

Scot


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## Normex (Feb 21, 2014)

sscotsman said:


> yes I know: "its not supposed to mean literal horses anymore"..
> but thats my point..if it doesnt mean literal horses anymore,
> then what _does_ it mean? no one knows.. it means nothing..
> 
> ...


 So true what you're saying about HP irrelevance and it's funny why most went with the cc's (maybe the courts decided?) as it also mean next to nothing since only the ft/lb would really be numbers one could relate to how far the snow is thrown or the grass for that matter. Ft/lb can at least be replicated to keep them honest as there is only one way to calculate it as opposed to hp.


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## GustoGuy (Nov 19, 2012)

Normex said:


> So true what you're saying about HP irrelevance and it's funny why most went with the cc's (maybe the courts decided?) as it also mean next to nothing since only the ft/lb would really be numbers one could relate to how far the snow is thrown or the grass for that matter. Ft/lb can at least be replicated to keep them honest as there is only one way to calculate it as opposed to hp.


Foot pounds of Torque. That is how most of the new Briggs engines are rated. Easier to measure too on a dyno.


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## rhenning (Sep 19, 2013)

Foot pounds can also be fudged if the manufacturer dynos 1000 engines and one is significantly higher than all the others and they use that as the norm. They have also done this with both HP and foot lbs of torque. CCs or Cubic Inches can't be fudged. They are what they are. Roger


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## Normex (Feb 21, 2014)

rhenning said:


> Foot pounds can also be fudged if the manufacturer dynos 1000 engines and one is significantly higher than all the others and they use that as the norm. They have also done this with both HP and foot lbs of torque. CCs or Cubic Inches can't be fudged. They are what they are. Roger


 The HP debacle was started because some companies fudged the numbers and in court they could not agree on a single derivation on HP calculation as there are a few. You are correct to say you cannot fudge the cc's numbers but small engine manufacturers have different ft/lb output for same cc's because of different carb jetting and timing so ft/lb should be the only output for small engines and can be replicated easily if a company is accused of fudging their numbers. With ft./lbs. and cc's we would get used to it in no time and associate the numbers with what an engine is capable of. Just saying.


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## rhenning (Sep 19, 2013)

You are right but there were 2 law suits of this type. The second one was on air compressors. In that case manufactuers put on the HP that the seller wanted not necessarily what most of the motors they used made. They did dyno tests on 1000 motors and used the highest one not the average. Consumers are so stupid they fell for it. Now most air compressor are sold by tank size and cubic foot per minute capacity of the pump at a given air pressure. If there is a way to fool consumers it is still being done. Roger


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## Coby7 (Nov 6, 2014)

Metric HP is slightly smaller than the British HP but they are close. (about 20watts)

The mechanical horsepower, also known as imperial horsepower, of exactly 550 foot-pounds per second is approximately equivalent to 745.7 watts.
The metric horsepower of 75 kgf-m per second is approximately equivalent to 735.5 watts.
The Pferdestärke PS (German translation of horsepower) is a name for a group of similar power measurements used in Germany around the end of the 19th century, all of about one metric horsepower in size.
The boiler horsepower is used for rating steam boilers and is equivalent to 34.5 pounds of water evaporated per hour at 212 degrees Fahrenheit, or 9,809.5 watts.
One horsepower for rating electric motors is equal to 746 watts.
Continental European electric motors used to have dual ratings, using a conversion rate of 0.735 kW for 1 hp
British Royal Automobile Club (RAC) horsepower is one of the tax horsepower systems adopted around Europe which make an estimate based on several engine dimensions.


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## Normex (Feb 21, 2014)

Coby7 said:


> British Royal Automobile Club (RAC) horsepower is one of the tax horsepower systems adopted around Europe which make an estimate based on several engine dimensions.


 ^^
That is certainly enough for the courts to have driven a nail in the HP debacle.


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## Coby7 (Nov 6, 2014)

I'm an electronics engineer and I go by the 746 Watt rule. It has always served me right whenever I had to replace a gas engine by an electric motor. I always ended on top with that formula because electric motors have instant torque. I was never caught ever with a bad calculation. I would look at the gas engine rated HP and replaced it with either a 110V or 220 Volt equivalent HP rating and I had more than enough horsepower to run what it was replacing. Never had a failure caused by this calculation method in 33 years so I stand by it.


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## suspicionofignorance2 (Jan 26, 2014)

SCFM vrs CFM when it comes to compressors...Keeps the public guessing..! Has anyone seen a good explanation of the different ratings.?


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## Coby7 (Nov 6, 2014)

SCFM vrs CFM has nothing to do with HP. The diference is compressed or un compressed. If the air coming out of a duct is under one pound of pressure it is CFM if it is under pressure then it is SCFM and calculated with a formula depending on pressure.


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## Normex (Feb 21, 2014)

Coby7 said:


> I'm an electronics engineer and I go by the 746 Watt rule. It has always served me right whenever I had to replace a gas engine by an electric motor. I always ended on top with that formula because electric motors have instant torque. I was never caught ever with a bad calculation. I would look at the gas engine rated HP and replaced it with either a 110V or 220 Volt equivalent HP rating and I had more than enough horsepower to run what it was replacing. Never had a failure caused by this calculation method in 33 years so I stand by it.


Then I don't know why you brought in your previous post if not just to reassert yourself, consider it done.


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