guys, pls help me define engine displacement in layman's terms.

how is it measured?  

Engine displacement, in a piston engine, defines the volume (normally stated in cubic inches, cubic centimeters, or litres) that is displaced as the pistons are moved from top dead center to bottom dead center.

I dunno how I can simplify it further though

from thermodynamics

displacement  =
3.14 x Cylinder radius^2 x Stroke (length)

Cylinder radius = bore/2
Stroke = Distance traveled by the Piston

Quote from: R-A-Y on August 03, 2004, 01:09:27 PM
Engine displacement, in a piston engine, defines the volume (normally stated in cubic inches, cubic centimeters, or litres) that is displaced as the pistons are moved from top dead center to bottom dead center.

I dunno how I can simplify it further though

Is the volume per piston/cylinder, or total of all cylinders?

its for all cylinders combined

laymans terms nga... hahahaha!!!

Quote from: latigid on August 03, 2004, 02:07:10 PM
from thermodynamics

displacement  =
3.14 x Cylinder radius^2 x Stroke (length)

Cylinder radius = bore/2
Stroke = Distance traveled by the Piston

Quote from: Blackblood on August 03, 2004, 09:39:22 PM
its for all cylinders combined

Ah, ok.  
That means a 2.4-liter, 4-cylinder engine for example, will have almost the same fuel consumption as that of a 6-cylinder engine with the same displacement.  I would guess that the latter will be slightly more economical since more cylinders suggests better engine efficiency.  Tama ba?

Quote from: dragonmate on August 04, 2004, 10:56:14 AM
Ah, ok.  
That means a 2.4-liter, 4-cylinder engine for example, will have almost the same fuel consumption as that of a 6-cylinder engine with the same displacement.  I would guess that the latter will be slightly more economical since more cylinders suggests better engine efficiency.  Tama ba?

I think not kasi there are more chambers (cylinders) that need a supply of the a/f mixture. Hence, more gasoline must be pumped para dun sa 6 cylinder, as opposed to the 4 cyl.

Quote from: speedyfix on August 04, 2004, 10:56:05 AM
laymans terms nga... hahahaha!!!

yap kasi nagtanong sya ng "how is it measured?"

Quote from: latigid on August 03, 2004, 02:07:10 PM
from thermodynamics

displacement  =
3.14 x Cylinder radius^2 x Stroke (length)

Cylinder radius = bore/2
Stroke = Distance traveled by the Piston

This is the correct formula but you have to multiply this by the number of cylinders pa .

Generally, the displacement tells you something about how much power an engine can produce. A cylinder that displaces half a liter can hold twice as much fuel/air mixture as a cylinder that displaces a quarter of a liter, and therefore you would expect about twice as much power from the larger cylinder (if everything else is equal). So a 2.0 liter engine is roughly half as powerful as a 4.0 liter engine.
siguro sa tagalog yung pwede nyang icompress at ilabas at d same time..dun sa mismong combustion shaft nya..hmmm

Quote from: Raymond on August 04, 2004, 03:08:48 PM
I think not kasi there are more chambers (cylinders) that need a supply of the a/f mixture. Hence, more gasoline must be pumped para dun sa 6 cylinder, as opposed to the 4 cyl.

Boss Raymond,
I don't get it.  Their total displacement volume is the same di ba?  Even if there are more cylinders, the volume of each cylinder is smaller.  Let's say you have two 2.4 liter engines, one is 6 cylinder and the other is 4 cylinder-- the 6 cylinder engine will have a cylinder size of 0.4 liter while the 4 cylinder will be larger at 0.60 liter.  So halos pareho pa rin uubusing air-fuel mixture ng bawat isa, diba?

4-cylinder versus 6-cylinder?  Same displacement?  Which has better fuel consumption?

Factors like mechanical losses (due to friction) and reciprocating mass come into play in favor of the 4-cylinder.  

The more moving parts an engine has, the more friction you get.  Dun palang lamang na ang 4-cyl.  But the more critical factor is reciprocating mass.  The smaller & lighter your pistons/piston pins/conrods are, the higher your potential rpm is and therefore the more power you can attain.

Lower mechanical losses combined with lower rpms means a 4-cylinder will consume less fuel.  The 6-cyl. will have a power advantage though.

Quote from: dragonmate on August 06, 2004, 09:04:50 AM
Boss Raymond,
I don't get it.  Their total displacement volume is the same di ba?  Even if there are more cylinders, the volume of each cylinder is smaller.  Let's say you have two 2.4 liter engines, one is 6 cylinder and the other is 4 cylinder-- the 6 cylinder engine will have a cylinder size of 0.4 liter while the 4 cylinder will be larger at 0.60 liter.  So halos pareho pa rin uubusing air-fuel mixture ng bawat isa, diba?

Yes, chambers may be smaller, but diba generally mas malakas ang 6-cyl sa 4-cyl kahit small displacement? So which almost means na mas malakas sa gas iyong 6-cyl.

Quote from: Raymond on August 06, 2004, 03:27:50 PM
Yes, chambers may be smaller, but diba generally mas malakas ang 6-cyl sa 4-cyl kahit small displacement? So which almost means na mas malakas sa gas iyong 6-cyl.

Mga Bossing,
Thanks for the explanation of Stradale and Raymond, which both make some sense.  However, please bear with me because it's not quite clear yet for me.
If I may change the question:  To make one complete revolution of the drive shaft, how much air-fuel mixture will be burned by a 2.4 liter, 4cyl engine, and by a 2.4 liter, 6 cyl engine?  
My answer is 2.4 liters for both.  That is because each piston/cylinder will make a complete cycle, regardless of the number of cylinders.  Hence, the total volume of fuel-air mixture that will be consumed in one revolution of the drive shaft will be the same as the total displacement of all cylinders, which is 2.4 liters. Mali ba yon?  
Note that I'm talking of fuel-air mixture, and not fuel alone.