Calculating Engine Size....

[slinky]

ok, so bore x pi x stroke x cylinders gives you the "swept" displacement ( I think!!) ... To get true CC (or CI) do you include combustion chambers? or is it just the swept displacement?

Cheers in advance!

slinky

[bikemadmod]

{[pi x (bore squared)]/4 } x stroke is the cc. (remember to times by no. of cylinders.. ..Doh!!)

[zaktoo]

(pi x bore squared (in mm)) / 4 * stroke (in mm) * number of cylinders / 1000 will give you the cubic centimetre volume.

Obviously if you use the bore & stroke in inches, don't divide by 1000 and you have cubic inches.

HTH

Ciao

Zak

[slinky]

zaktoo said:

(pi x bore squared (in mm)) / 4 * stroke (in mm) * number of cylinders / 1000

What is the relevance of the 4 in this equation?

I understand the equation for calculating the volume of a cylinder and multiplying it up by the number of cylinders... what I'm asking is do I need to include combustion chambers as well?

slinky

[Zad]

The head is not within the swept area and so not included. A bigger head volume would only give a lower compression and cannot affect the swept volume. Whilst forced induction and resonances that "suck" the exhaust gas out and produce a partial vacuum in the cylinder would alter the virtual swept volume, they are not easily calculated and depend on many variables.

Mike

[zaktoo]

slinky said:

zaktoo said: (pi x bore squared (in mm)) / 4 * stroke (in mm) * number of cylinders / 1000 What is the relevance of the 4 in this equation?

Well this bit is easy - the volume of a cylinder is the radius squared, multiplied by pi and the height of the cylinder. Bore is the diameter, so must be divided by 2 before being squared. You could re-write that as (bore/2) * (bore/2), which = bore squared / 4

Ciao

Zak

[deltafox]

Surely its Pi x R squared X stroke x number of cylinders/1000 ? Where radius squared is the radius of the bore and not the bore diameter?

[zaktoo]

deltafox said:

Surely its Pi x R squared X stroke x number of cylinders/1000 ? Where radius squared is the radius of the bore and not the bore diameter?

Bore is the diameter of the cylinder, therefore the radius is bore/2 ;-)

[mindgam3]

Area of circle = (pi x diamter^2) /4
Area of circle = pi x radius^2

Either can be used, but seeing as though bore is diamter, you may as well keep it in diamter to calculate swept volume...