cc to horsepower

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  #1  
Old 12-06-09, 09:16 AM
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cc to horsepower

Snowblower season is now upon us. Going to buy a new snowblower this year? But you don't know how powerful it is? 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. Some of these were taken from ads that stated "replacement 179 cc engine for 5hp snowblowers". This just lets you know that a 179cc engine can NOT be a 10 hp engine. Hope this helps in deciding which snowblower you buy.

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
 
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Old 12-06-09, 09:53 AM
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Oh, I don't know; an Indy car gets about 700 HP out of 4.0L (4,000 cc's) or 1 hp per 5.7 cc's, so in theory you could get about 32 HP out of 179cc. Of course I wouldn't want to be the guy driving it.
 
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Old 12-06-09, 10:06 AM
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The numbers indypower1 posted are good numbers for general conversion of STOCK OPE engines.

Briggs and Stratton is now using Torque rating instead of HP. If I remember correctly a federal law will require all OPE engines to use torque rating in the future, I could be wrong. Below is some conversions I found and an article.

205 cc = 8 to 9 Gross Torque = 5.5 to 6 hp

250 cc = 11 to 11.5 Gross Torque = 7 to 8 hp

305 cc = 13.5 to 14.5 Gross Torque = 9 to 10 hp

342 cc = 15.5 to 16.5 Gross Torque = 11 to 12 hp

http://www4.briggsandstratton.com/mi...P3845_1106.pdf

Briggs and Stratton model numbers convert to cubic inches

1 cubic centimeters = 0.061 cubic inches. That means whenever you want to convert a cc quantity into ci just multiply it by 0.061.
 
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Old 12-06-09, 07:53 PM
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I have to wonder at the Torque numbers being higher than the HP numbers... These are fairly primitive engines with 1 piston & if you look @ multi cyl overhead cam fuel injected engines, the torque numbers are usually lower than HP even @ there peak RPM's... I know this is what they claim but math says a 12 HP engine has 8 ft/lbs (Torque = HPxRPM/5250) Someone correct me if I'm wrong,, but the numbers they claim don't add up,,,at least to me... Roger
 
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Old 12-07-09, 05:08 AM
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Well, there are all kinds of ways to skew numbers. You know the old saying, there are three kinds of lies - lies, damn lies, & statistics.
 
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Old 12-07-09, 05:54 AM
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Originally Posted by hopkinsr2 View Post
I have to wonder at the Torque numbers being higher than the HP numbers... These are fairly primitive engines with 1 piston & if you look @ multi cyl overhead cam fuel injected engines, the torque numbers are usually lower than HP even @ there peak RPM's... I know this is what they claim but math says a 12 HP engine has 8 ft/lbs (Torque = HPxRPM/5250) Someone correct me if I'm wrong,, but the numbers they claim don't add up,,,at least to me... Roger
There are a few things that will change the calculated torque. For one thing Hoppy Full load torque is HPx5252/RPM(How to Calculate a Motor Torque | eHow.com)
12HPx5252=6302, 63024/3600RPM=17.5

Another thing especially with auto's is where they measure the torque. It will be less if measured at the drive wheels than at the crankshaft. I can only imagine they must get creative with the other formula for Torque which is T= F (force in lbs.)xD(distance in ft.)
Actually a single cylinder engine is more efficient than multi cylinder engine. Likewise once you start adding transmissions and gearing, further efficiency is lost.
 
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Old 12-08-09, 09:03 AM
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Hopkins I can't believe you gave up that easy I was hopeful of an intelligent discussion...with you providing the intelligence part

At any rate, another consideration would be if the formula T=F x D was actually used, then the momentum or "mass in motion" would be a determining factor. With higher performance engines lighter weight materials are used throughout which allows for higher RPM's and in calculation higher HP. However when you transfer that to torque, less mass in motion will result in less torque or actual work. More HP results in more speed once moving, but full load torque is like dropping the clutch at a stand still or moving dead weight and momentum can play a big part.
For this reason I will take a straight six in a work truck over a V-8 any day of the week. Generally speaking I think an inline will have better torque/horsepower rating than a V config will. Flat, boxed or opposed config would be second for torque but first for longevity IMO....
 
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Old 12-08-09, 09:28 AM
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When you get into the exotic engines, everything changes.

A Formula 1 engine is a 2.4 or 2.0 liter V8 (down from the old V10s and V12s) that puts out well over 850 hp and is governed to limit revs to less than about 19,000 rpm (220 mph). It weighs about 225 #. It is designed to not just go fast, but be able to push a 1220# car around 10 to 15 corners (left and right) in each lap. Stopping and acceleration are the main criteria. The engines are only about $500,000+, but you still need a 747 for the cars, exercise gym and drivers. The 300 engineers (electronics, engine and tires) follow in another 747. - The maintenance is probably quite high, especially when you travel with $250,000 of spare rotors per car.

It is interesting, but I don't think I would go for a Ferrari or Mercedes for my snow blower. I loved my old 8 hp in northern Michigan, but could never get out early enough to beat my neighbors to blow my sidewalk and driveway.
 
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Old 12-08-09, 05:32 PM
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Sorry BFH,, I didn't go away,, but we're supposed to get 30 cm (12 inches ) of snow tomorrow & everyone is expecting me to fix there snowblower NOW.. A transmission or a rear axle is a torque multiplier,, so if they measure it at drive wheels,, it should be heigher than the engine can generate,,, You'r right with the math tho,, I dont know where I came up with that,, the old memory isn't so good as I think that's the HP formula.. Torque is the twisting force on the crankshaft & I really don't see how 1 power impulse every 2 crank revs can be more efficient than a multi cyl engine where you may even have a power overlap with more than 1 cylinder at a time turning the crank,,,Just thinking out loud... Roger
 
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Old 12-08-09, 05:55 PM
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No problem with Excel.

Fitting a best straight line to the OP's data gives HP = cc x (0.038) - 2.0.

So, for 291 cc the formula gives you 9.1 hp (vs 9.0 actual data), and for each additional cc you get 0.038 hp additional, on average.
 
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