Hello,

I know, I've got such a novice question, but what does cubic inch
displacement really mean? I know it can be expressed in "cc"s or even
liters, but what is it really measuring?

Thanks,

Jeff

JMI wrote:
The volume "displaced" by the pistons in all the cylinders.

In article <edf27f$fd3$1 (AT) news04 (DOT) infoave.net>,
"JMI" <ingramje (AT) gmail (DOT) com> wrote:

OK, let's not "give him a fish" - Let's "teach him to fish" right from
the git,-go, huh?

Pistons go up and down inside a cylinder. One end of the cylinder, the
head, is fixed. The piston is the other end of the cylinder. In between
the piston and the head is some volume.

When the piston is at the bottom of its stroke, the volume is X cubic
"Units" - Units might be inches, centimeters, cubits, football fields -
Whatever...

When the piston is at the top of its stroke, the volume is much smaller
- Let's call it Y cubic Units.

The motion of the piston from bottom of stroke to top of stroke is said
to "displace" a certain number of cubic units by making the cylinder's
volume get smaller. The exact number depends on cylinder/piston diameter
and length of stroke.

Therefore, displacement of one cylinder, D, is figured as:

D = (X - Y)

or the difference between the cylinder's volume when the piston is at
the bottom of its stroke, and when it's at the top.

Assuming you're using inches for your units, do that math, then multiply
by the number of cylinders the engine has, and you get the engine's
total "Cubic Inch Displacement" number. Use centimeters, and you get the
engine's displacement in CCs. Likewise for whatever other unit you care
to convert to/work with.

--
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or the subject of the message doesn't contain the exact text "PopperAndShadow"
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"Don Bruder" <dakidd (AT) sonic (DOT) net> wrote

Good start, Don.

We can also tell him that large displacement numbers, whether in cubic
inches or in litres, give you
the potential for more powerful engines since this is the amount of fuel/gas
mixture you can burn
in the engine in a complete revolution.

So, to the OP, a 7 litre (or 7000 cc) engine has the rough potential to put
out twice the power as
a 3.5 litre engine (3500 cc) ALL OTHER FACTORS BEING EQUAL.

There are many ways to make the factors unequal, and that is what we
hotrodders, benchracers,
mechanics and enthusiasts are often interested in. For example, a highly
developed 2 litre engine
can easily put out a 750-1000 horsepower, while a detuned 4 litre engine
might not even make a
hundred.

That is one of the things we enthusiasts love to play with.

In article <V_HKg.23615$gY6.11487 (AT) newssvr11 (DOT) news.prodigy.com>,
<HLS (AT) nospam (DOT) nix> wrote:

Guess that means my 2 liter isn't all that "highly developed" - 74 HP @
2750 RPM is its peak according to "The Book". (Big surprise, as it was
sold to power a "sporty economy car", not a tire-eating monster )

--
Don Bruder - dakidd (AT) sonic (DOT) net - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... <http://www.sonic.net/~dakidd> for more info

HLS (AT) nospam (DOT) nix wrote:
For a four cycle gasoline engine wouldn't you need two full revolutions
to burn the full displacement?

That clears that up! Thanks!

Jeff

<HLS (AT) nospam (DOT) nix> wrote

--
Please Note New address
daniels_sam (AT) bellsouth (DOT) net
"JMI" <ingramje (AT) gmail (DOT) com> wrote

Jeff, should you ever wish to calculate the cubic inches (or
centimeters) of any engine, use the formula for finding volume of ONE
cylinder--any cylinder, like a can of tomato juice. V=(Pi) (r) (r) (h).
[[Pi = 3.14, a constant value. R, the radius, = ½ the diameter (in engines,
the diameter = the bore). H=the stroke.]] Now the formula becomes V=(3.14)
(0.5 bore) (0.5 bore) (stroke). Then multiply this cylinder's volume by the
number of cylinders to get the "volume" of the total displacement of the
engine. s

"Daniel" <nospampls2002 (AT) yahoo (DOT) com> wrote

Yes, you would, but the displacement by the pistons is achieved in one
single
revolution. In a four stroke cycle, the valving, spark, etc allow each
cylinder
to fire every other revolution, but the cylinder is still swept once per
revolution.

I realize that this could have been misinterpreted, and perhaps I should
have
explained it better in the beginning.

"Don Bruder" <dakidd (AT) sonic (DOT) net> wrote

Im glad we dont have to support the expenses that would go along with a
'highly developed' 2 litre engine, Don, aren't you?

I was thinking about the Formula I engines when I made that statement,
which are-to me- marvels of engineering. That one can put together a
small displacement engine which can turn 20,000 rpm for hours and put out
astronomical power ratings is pretty spectacular.