What does cubic inch displacement really mean?

#11

JMI wrote:

Quote:

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

The total volume swept out by all the cylinders (not including

combustion chamber volume).

IOW, the surface area of each piston (pi*(bore/2)^2) multiplied by the
stroke, multiplied by the number of pistons.

#12

Daniel wrote:

Quote:

HLS (AT) nospam (DOT) nix wrote:

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.

=================
For a four cycle gasoline engine wouldn't you need two full revolutions
to burn the full displacement?

When it comes to calculating volume flow, that is correct. Of course
that assumes 100% volumetric efficiency (the engine moves an amount of
air/fuel mix EXACTLY equal to its displacement on every full power
cycle, or 2 rotations in the case of a 4-stroke). But volumetric
efficiency is all over the map. An idling 440 cubic inch engine, for
example, only moves a tiny fraction of 440 cubic inches of air every 2
revs. On the other hand, at its peak power RPM the same engine (even
without supercharging) might move MORE than 440 cubic inches every 2
turns (more than 100% VE) because of ram-induction effects in the intake
manifold. Turbo-charged or super-charged engine consistentely operate at
more than 100% VE whenever there is boost.

#13

Daniel wrote:

Quote:

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

Yes.....the 4-stroke cycle does take two revolutions to complete one
combustion cycle.

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What does cubic inch displacement really mean?

Cars (General) General Cars Discussions (alt.autos)

Re: What does cubic inch displacement really mean? - 09-05-2006 , 10:29 AM

Re: What does cubic inch displacement really mean? - 09-05-2006 , 10:36 AM

Re: What does cubic inch displacement really mean? - 09-05-2006 , 10:47 AM