motor displacement formula?

[jlevasseur]

I know there are sites that I can got to and input the bore and stroke to figure out the cc displacement but I was wondering what the formula was so I could do it myself just to know. For example what is a 18 mil DM 78mm bore?? something like a 680 or so right? the formula would be sweet thanks.

[dajogejr]

Bore X Bore X Stroke X an engineering constant / number of cylinders.

 

I can't find that constant for the life of me.

But here's an easy to use calculator.

Use millimeter as the unit of measurement.

 

http://www.bgsoflex....splacement.html

 

Wait, .0031416 is the number.

So, I have a 68 bore cub with a 64 mm stroke (10 mil cub)

 

68X68X64X.0031416 /2 = 464.8 cc...or a 465 cub as they're called.

[alcoholbanshee]

Bore X Bore X Stroke X an engineering constant / number of cylinders.

 

I can't find that constant for the life of me.

But here's an easy to use calculator.

Use millimeter as the unit of measurement.

 

http://www.bgsoflex....splacement.html

 

Wait, .0031416 is the number.

So, I have a 68 bore cub with a 64 mm stroke (10 mil cub)

 

68X68X64X.0031416 /2 = 464.8 cc...or a 465 cub as they're called.

 

 

I use bore x bore x stroke x .0007854 x # of cylinders = displacement........................... all numbers in miilimeters...........

[dajogejr]

Yes sir...that works too!

If you multiply .0007854 by 4, you get the same number as an engineering constant (.0031416)

 

6 of one half dozen of the other!

[Bansh-eman]

I use bore x bore x stroke x .0007854 x # of cylinders = displacement........................... all numbers in miilimeters...........

I use this same formula

[alcoholbanshee]

Yes sir...that works too!

If you multiply .0007854 by 4, you get the same number as an engineering constant (.0031416)

 

6 of one half dozen of the other!

 

Yeah I am not an engineer......I work for a living....................

Edited December 22, 2009 by alcoholbanshee

[jlevasseur]

sweet guys.....thanks. Is there a easy way to figure out the constant without remembering it?? And how about figureing out the mm of a stroke? How would you figure out what a 18 mil stroke would be? thanks for all the help!!

[dajogejr]

sweet guys.....thanks. Is there a easy way to figure out the constant without remembering it?? And how about figureing out the mm of a stroke? How would you figure out what a 18 mil stroke would be? thanks for all the help!!

 

Nope...you remember the number or search for a displacement calculator online...

 

A stock banshee stroke is 54mm (yeah, another number to remember )

So add the 18 to 54.

[Confederate350]

bore x bore x stroke x # of cylinders x .7862 = displacement

[rubberneck]

That magic constant is simply pie. From geometry guys remember that class. 3.1417. The reason the constant is 0.0031417 is because your measurements are in mm and you want your displacement in cc

[jlevasseur]

sweet guys thanks!!!!!!!!!!!!!!1

[slowblueshee2]

1/2 the bore x 1/2 the bore x stroke x 3.14 x number of cylinders. But you have to move the decimal point for example a stock engine is 64bore x 54stroke. It would be 3.2 x 3.2 x 5.4 x 3.14 x 2 = 347.25888.

Say a 10 mil dm. 78bore x 64stroke. It would be 3.9 x 3.9 x 6.4 x 3.14 x 2 = 611.32032

[alf44]

This is the easiest i have found. Just punch in the numbers

 

http://www.havocperformance.com/ENGINECALCULATOR.htm