You cant calculate the horsepower, only measure it.
There are too many variables to calculate the horsepower. Though many people have posted estimates.
I was sent a formula for calculating the CID of an engine based on bore and stroke, in inches.
bore x bore x stroke x .7854 x number of cylinders = total CID
Have not yet been able to verify it though.
THIS RULE OF THUMB IS WIDELY SHOW IN PERFOMANCE OF A DODGE VIPER VS MERCIELAGO LAMBERGINI ON A 1\4 MILE TRACK, THE VIPER HAS 500HP AND THE LAMBO HAS HP640. NOT TO MENTION TOP SPEED BUT THATS A DIFFERENT MATTER.
YOU TAKE 16.39 MULTIPLY BY ENGINE SIZE AND IT WILL EQUAL CC
EXAMPLE 107" MOTOR X 16.39 = 1753.73 YOU WOULD THEN ROUND OFF
AND YOUR ANSWER IS 1754
A 107 ENGINE = 1754 CC
AND I AM A GIRL!
A couple of things real quick:
a.) this does not answer the OP's question of cc to hp conversion (as this is impossible), and b.) your conversion of cubic inch to cubic centimeter might have be better understandable if you said 'ci'' instead of '"' (as in '107 ci = 1754 cc') when referring to cubic inches, but whatever, perhaps I'm just being pedantic.
Very helpful discussion for my in spite of trying to do the 'impossible'. Im chossing between a 3 HP electrice chain saw, and a 40cc gas saw, as a back up tool The price differential is over a hundred dollars, and Now I don't think it worth it, as it is a back up. I liked the eye ball 15-17 mulitplier, ( as in 16.39) I'm just a guy, but I see nothing wrong with pedantry. thank you all.
form what i have read on this topic. and what i wont to know is my go-ped is from the 50' im trying to find rings for it. the motor is a 50 or 55 cc engine, witch happens to be close to the piston size of a weedeater or a chainsaw. the measurments for theis type of motors are in horsepower. by using the horsepower calculations i can find the write piston size of a small engine for my ring replacement since they do not make after market parts for a Benelli 250D from the 1955
There are many verables that determine Horse Power. You may have two identical engines that put out different horse power. It is determined by displacement, Compression Ratio, Fuel mixture, engine design, ignition and valve timing.
Horse Power or (BHP) 1BHP = 550 FtLb per second
Example: For Calculating FtLb
Work= Distance X Force (5Ft X 10Lb = 50FtLb)
Power= Work / Time (50FtLb / 2 seconds = 25 Foot Pounds per Second)
If you want to figure out CC for an engine you use
Displacement= Bore X Bore X 0.7854 X Stroke, X number of cylenders
Example 5.4(Bore) X 5.4(Bore) X 0.7854(Constant) X 5.4(Stroke) X 1(number of cylenders) = 123.672 CC
and if you need to convert CI to CC (1 CI = 16.387 CC)
That being said the best way to get an accurate HP is to put your vehicle on a Dyno or call the manufacture.
Just trying to provide some food for thought.
Have a good day.
Use cc'c divided by 42.3 and it would give you the app. Hp. For instance a 148 cc lawn mower at a store is equivlant to a 3.5 Hp, engine . and a 1.73 cc app. 4hp. Still don't use this as a rule on used engines , they loose hp as used. This is just a calculation to give you the basics . in the perfect world
This may be a new thread, but my question involves what may be a more accurate horsepower rating for military standard engines? For example the 4A032-4 Military Standard engine produced by Teledyne is listed as a 6 hp. engine. But the thing has 525 cc's. A 4-stroke motorcycle engine of this size may create between 30 and 40 hp. The Military is known for under-rating these Mil. Std. engines, but I need to know what a realistic or real world Hp. rating might be.
The military spec may measure the horsepower at a specific RPM. Depending on the RPM you would have greatly different horsepower output. For example, a diesel engine can produce greater horsepower at low RPMs then a gasoline engine.
The Honda 499 cc racing engine has a bit over 200 horsepower.
Though realistically its just not a good idea to try and estimate horsepower based strictly on engine size. They are just not related enough.
if you have a 1000 cc engine and say you have 100 hp. what if you have a 1000 ccc engine and put a turbo on it? or a cam? or a bigger carb? You have more horsepower but the same 1000 cc motor. If you want to find the hp of an engine you have what I do is go too google and type in the engine brand and cc size and model. then also put hp for the search word too. This will usually direct you to a site that will tell you.
There Is A Way You Can Calculate Cc's To Hp But Since It Depends On The Parts The Motor Has You Will Have To Find Out Your Engine Parts Specs. There Are A Couple Of Programs Performance Trends Makes That Will Get You Within 3 Hp Of Your Accurate Power. But Using The Performance Trends Programs Are Very Difficult And You Must Know Alot About Engines. So You Can Mess Around With A Free Program, Or Spend Up $500 At A Shop With A Dinomometer.