http://www.circletrack.com/enginetech/c ... index.html
original source read the links theres a ton of info I can,t post
http://mk3ukr-supra.net/Combustion%20pa ... arland.pdf
heres a burn pattern thats the result of an even burn that produces good power
Combustion Patterns:
The Telltale Signs of Power...or the Lack Thereof
Editor’s Note: The reading of postburn
residue on combustion surfaces
(pistons, valves and chambers) can
reveal much about why a given engine
performs as it does. This lecture is
directed to understanding some of the
results that are described by “readingâ€
such patterns. It includes comments
about various engine components or
characteristics that affect combustion
efficiency…in the burn space. Some of
the following discussion includes portions
of previously discussed material,
primarily as a platform for new information
that will expand upon the overall
combustion process.
BASIC INFORMATION
The mixing of air and fuel - Since
air and fuel must be mixed in order to
support combustion, the manner and
extent to which this blending is accomplished
relates to combustion efficiency.
As the so-called “oxidation reduction
reaction†process begins (the reduction
of air and fuel to heat), the time required
to accomplish this process is keyed to
fuel droplet size. For example, the larger
the droplet, the longer the time required
for it to “burn.†Conversely, the smaller
the droplet the less time is needed.
We know that in a given sample of
mixed air and fuel, there are variations
in droplet size. If we measure this mixing
based on the need for having all
droplets the same size (for uniform
burning rate), then the term “atomization
efficiency†becomes noteworthy.
Mixtures that contain a wide variation in
droplet size tend to burn at irregular
rates, the smaller droplets being consumed
faster than the larger ones. This
unevenness creates problems determining
specific spark ignition timing and
proper fuel volume supplied.
“Since air and fuel
must be mixed in order
to support combustion,
the manner and extent
to which this blending
is accomplished relates
to combustion
efficiency.â€
What’s important to remember is that
atomization efficiency often reflects in
the residue left on piston crowns and
combustion chambers. And in some
instances, these patterns can also be
detected on spark plug housings by the
use of magnification. Just because air
and fuel are mixed efficiently at the point
they enter an intake manifold, it does
not necessarily follow that efficient
mixing will find its way into the combustion
space. Directional and pressure
changes from the mixing point (even if in
the combustion chamber itself) to the
end of combustion can negatively affect
combustion efficiency and power.
What the patterns can mean -
Generally, black or dark combustion
residue (even if it’s oily) tends to suggest
a fuel-rich mixture. As the mixture trends
more toward a fuel-lean ratio, the dark
color begins to lighten into a tan or light
gray shade. An absence of color usually
suggests a correspondingly absence of
any combustion at all…at least near the
surface that’s clean.
There is also an opportunity examine
the direction of flame travel (or “mixture
motionâ€) by studying residue patterns.
Plus, the detrimental effects of piston
crown shapes (protrusions often used to
increase mechanical compression ratio)
can be noted by observing combustion
residue locations.
Identifying “Goodâ€
and “Bad†Patterns
The purpose of this discussion is to
focus on patterns that relate to the production
of power. Those that pertain to
problems such as coolant intrusion into
the combustion space, blown cylinder
head gaskets or conditions that also
reduce power or cause damage. The
“good†and “bad†patterns about
which we’re speaking point to inconsistent,
inadequate or improper combustion
efficiency… the results from which
tend to reduce the amount of power
available.
It is not always necessary for the
entire combustion surface of a
piston to be covered with residue.
original source read the links theres a ton of info I can,t post
http://mk3ukr-supra.net/Combustion%20pa ... arland.pdf
heres a burn pattern thats the result of an even burn that produces good power
Combustion Patterns:
The Telltale Signs of Power...or the Lack Thereof
Editor’s Note: The reading of postburn
residue on combustion surfaces
(pistons, valves and chambers) can
reveal much about why a given engine
performs as it does. This lecture is
directed to understanding some of the
results that are described by “readingâ€
such patterns. It includes comments
about various engine components or
characteristics that affect combustion
efficiency…in the burn space. Some of
the following discussion includes portions
of previously discussed material,
primarily as a platform for new information
that will expand upon the overall
combustion process.
BASIC INFORMATION
The mixing of air and fuel - Since
air and fuel must be mixed in order to
support combustion, the manner and
extent to which this blending is accomplished
relates to combustion efficiency.
As the so-called “oxidation reduction
reaction†process begins (the reduction
of air and fuel to heat), the time required
to accomplish this process is keyed to
fuel droplet size. For example, the larger
the droplet, the longer the time required
for it to “burn.†Conversely, the smaller
the droplet the less time is needed.
We know that in a given sample of
mixed air and fuel, there are variations
in droplet size. If we measure this mixing
based on the need for having all
droplets the same size (for uniform
burning rate), then the term “atomization
efficiency†becomes noteworthy.
Mixtures that contain a wide variation in
droplet size tend to burn at irregular
rates, the smaller droplets being consumed
faster than the larger ones. This
unevenness creates problems determining
specific spark ignition timing and
proper fuel volume supplied.
“Since air and fuel
must be mixed in order
to support combustion,
the manner and extent
to which this blending
is accomplished relates
to combustion
efficiency.â€
What’s important to remember is that
atomization efficiency often reflects in
the residue left on piston crowns and
combustion chambers. And in some
instances, these patterns can also be
detected on spark plug housings by the
use of magnification. Just because air
and fuel are mixed efficiently at the point
they enter an intake manifold, it does
not necessarily follow that efficient
mixing will find its way into the combustion
space. Directional and pressure
changes from the mixing point (even if in
the combustion chamber itself) to the
end of combustion can negatively affect
combustion efficiency and power.
What the patterns can mean -
Generally, black or dark combustion
residue (even if it’s oily) tends to suggest
a fuel-rich mixture. As the mixture trends
more toward a fuel-lean ratio, the dark
color begins to lighten into a tan or light
gray shade. An absence of color usually
suggests a correspondingly absence of
any combustion at all…at least near the
surface that’s clean.
There is also an opportunity examine
the direction of flame travel (or “mixture
motionâ€) by studying residue patterns.
Plus, the detrimental effects of piston
crown shapes (protrusions often used to
increase mechanical compression ratio)
can be noted by observing combustion
residue locations.
Identifying “Goodâ€
and “Bad†Patterns
The purpose of this discussion is to
focus on patterns that relate to the production
of power. Those that pertain to
problems such as coolant intrusion into
the combustion space, blown cylinder
head gaskets or conditions that also
reduce power or cause damage. The
“good†and “bad†patterns about
which we’re speaking point to inconsistent,
inadequate or improper combustion
efficiency… the results from which
tend to reduce the amount of power
available.
It is not always necessary for the
entire combustion surface of a
piston to be covered with residue.