Characteristics of running lean vs. rich
#2
02-05-2004, 01:09 AM
#3
02-05-2004, 02:31 AM
Characteristics of running lean vs. rich
Check out duncanracing.com, go to the tech center under tech documents choose the article about "Keihin carb. jetting". There is a very good article about tuning a keihin carb., it has great information in regards to jetting and the way in which your bike will react with different jetting set-ups. Hope this helps. Ride On...Mudfoot
#5
02-05-2004, 03:50 PM
Characteristics of running lean vs. rich
I've used this method for years. It has never failed me in absence of a WBO2 sensor.
Do not try to read plugs with the naked eye, you'll miss alot of important subtleties. Try to use the same batch / type of fuel when tuning; if you have a tankful of month old 93 on day one, and then refill the bike with fresh fuel on day two, you're plug readings can change.
Reading Plugs:
***This applies to Naturally Asparated as well as Nitrous Engines***
This is valid for track only(not street driving) if you shut your engine off at the finish line, then remove the plugs for reading. Or if you are on the dyno for full load acceleration or steady state dyno tests. It's best to view plugs with a 10x power illuminated magnifying type glass.
What each part of a plug signifies:
"Ground Strap" = Heat Range
"Plug's Base Ring" = Jetting
"Porcelain" = signs of preignition/detonation (not jetting)
Heat Range:
The ground strap indicates the heat range of the spark plug. If the "color" of the ground strap "changes" too close to the ground strap's end, (located above the center electrode), then the heat range is "too cold", meaning that the strap is loosing heat too quickly to the base ring. It is not able to burn off deposits until near its end. If the "color" of the strap changes near where it is welded/attached to the base ring (last thread ring), then the plug heat-range is "too hot", because heat is not being tranferred or cooled from the strap to the base ring quickly enough. The strap might begin to act like a "glow-plug". Eventually
causing preignition and/or detonation later on. The proper heat range is when the "color" is at the half-way point on the strap. This means the plug is neither too cold or too hot.
Color; Meaning the evidence of heat or lack of heat by the appearance dark vs lightened color of metal.
Jetting:
The air/fuel mixture ratio shows up on the base ring. This is the last thread ring, it has the strap welded to it. You want a full turn of light soot color on the base ring!!! If you want to tune for maximum power, then you want 3/4 to 7/8ths of a full turn of light soot color to show up on the base ring. This is on ragged-edge of being too lean, but will make the most HP in most engines. To be safe, leave it at a full turn of light soot color. If the base ring has a full turn of color, but there are "spots" of heavy build-up of "dry soot" on top of color, then jetting is too rich.
****If the base ring has a full turn of color with some spots of heavy dry
soot, then jetting is too rich, REGARDLESS, if the porcelain is
"BONE-WHITE", jetting is still TOO RICH.****
* Do not look at the porcelain to read jetting. *
Pre-ignition/Detonation:
The porcelain shows up pre-ignition and detonation (timing/octane). It will not accurately reveal jetting/air/fuel ratios. To look for the first/beginning signs of detonation, search the white porcelain for tiny black specks or shiny specks of aluminum that have fused to the porcelain. When detonation occurs, part of the air/fuel mixture explodes instead of burning, the explosion is heard as a "metallic knock", this audible knock is the result of a sound shock-wave, this shock wave travels back and forth across the
clearance volume "disrupting" the cooler boundary layer gases that cover the entire clearance volume area. This disruption allows "more" heat to be transferred into parts, especially, domes/piston crown,...along with the very rapid rise in pressure like a hammer blow, pistons can get torched with
melted sides and holes !!! With the early signs of detonation, the shock-wave will also rattle rings causing the tiny amounts of oil that now gets by rings, to be fused to the white porcelain as tiny black specks, also fused as specks are soot that was clinging to clearance volume surfaces in the relatively "still-air" of the boundary layer. One step beyond the black specks, will be tiny specks/***** of aluminum coming off the pistons that will be fused to white porcelain,....the next step to be reached is occasional pieces of the
porcelain being broken-off as detonation gets worse, etc. Soon after that are holes, blown head gaskets, broken connecting rods, etc.
*** Additional signs of beginning detonation are piston rings. By comparing ring's "free diameter" to "out-of-box" free diameters of new unused rings will reveal beginning of detonation before much harm is caused !!! This is a result of the above previous explanation about heat being transferred more readily because the of the relatively insulating/cooler boundary layer being disrupted by the shock-wave. A piston ring is a simple spring, when a spring is over-heated it will loose tension.
****Also on the "Center Electrode", something else to look for. The very tiny, sharply defined porcelain "ditch" that encircles the center electrode, will also show up early signs of pre-ignition or detonation as the wrong heat-range. Look for signs of the ditch beginning to fill up with melted
porcelain. You will need a 5x or 10x magnifying glass to check this.
RECOMMENDED SPARK PLUGS FOR NITROUS APPLICATIONS
FROM PERSONAL EXPERIENCE: **I like the NGK line of plugs because
they are the easiest to read. Also a good plus is the Autolite brand. They
have the hardest non-eroding electrode and will absorb more heat before
burning off.
NON RECOMMENDED SPARK PLUGS : Any resistor type spark plug.
Split Fire and Platinum spark plugs run too hot and cause "Detonation"
because they are self cleaning and run hotter then normal plugs. Stay away
from projected tip plugs with Nitrous, to much plug in the hole and easier
to lose a tip.
**When tuning a new combination, I tend to stay away from plugs that use an inconel "strap"....I like to utilize the softer steel ground strap of a "regular" plug as a fuse (it will burn off and cause a miss, rather than hurt the engine). Hope this helps....it's kinda verbose, but if you want to get it right....there are no shortcuts.
Steve
Do not try to read plugs with the naked eye, you'll miss alot of important subtleties. Try to use the same batch / type of fuel when tuning; if you have a tankful of month old 93 on day one, and then refill the bike with fresh fuel on day two, you're plug readings can change.
Reading Plugs:
***This applies to Naturally Asparated as well as Nitrous Engines***
This is valid for track only(not street driving) if you shut your engine off at the finish line, then remove the plugs for reading. Or if you are on the dyno for full load acceleration or steady state dyno tests. It's best to view plugs with a 10x power illuminated magnifying type glass.
What each part of a plug signifies:
"Ground Strap" = Heat Range
"Plug's Base Ring" = Jetting
"Porcelain" = signs of preignition/detonation (not jetting)
Heat Range:
The ground strap indicates the heat range of the spark plug. If the "color" of the ground strap "changes" too close to the ground strap's end, (located above the center electrode), then the heat range is "too cold", meaning that the strap is loosing heat too quickly to the base ring. It is not able to burn off deposits until near its end. If the "color" of the strap changes near where it is welded/attached to the base ring (last thread ring), then the plug heat-range is "too hot", because heat is not being tranferred or cooled from the strap to the base ring quickly enough. The strap might begin to act like a "glow-plug". Eventually
causing preignition and/or detonation later on. The proper heat range is when the "color" is at the half-way point on the strap. This means the plug is neither too cold or too hot.
Color; Meaning the evidence of heat or lack of heat by the appearance dark vs lightened color of metal.
Jetting:
The air/fuel mixture ratio shows up on the base ring. This is the last thread ring, it has the strap welded to it. You want a full turn of light soot color on the base ring!!! If you want to tune for maximum power, then you want 3/4 to 7/8ths of a full turn of light soot color to show up on the base ring. This is on ragged-edge of being too lean, but will make the most HP in most engines. To be safe, leave it at a full turn of light soot color. If the base ring has a full turn of color, but there are "spots" of heavy build-up of "dry soot" on top of color, then jetting is too rich.
****If the base ring has a full turn of color with some spots of heavy dry
soot, then jetting is too rich, REGARDLESS, if the porcelain is
"BONE-WHITE", jetting is still TOO RICH.****
* Do not look at the porcelain to read jetting. *
Pre-ignition/Detonation:
The porcelain shows up pre-ignition and detonation (timing/octane). It will not accurately reveal jetting/air/fuel ratios. To look for the first/beginning signs of detonation, search the white porcelain for tiny black specks or shiny specks of aluminum that have fused to the porcelain. When detonation occurs, part of the air/fuel mixture explodes instead of burning, the explosion is heard as a "metallic knock", this audible knock is the result of a sound shock-wave, this shock wave travels back and forth across the
clearance volume "disrupting" the cooler boundary layer gases that cover the entire clearance volume area. This disruption allows "more" heat to be transferred into parts, especially, domes/piston crown,...along with the very rapid rise in pressure like a hammer blow, pistons can get torched with
melted sides and holes !!! With the early signs of detonation, the shock-wave will also rattle rings causing the tiny amounts of oil that now gets by rings, to be fused to the white porcelain as tiny black specks, also fused as specks are soot that was clinging to clearance volume surfaces in the relatively "still-air" of the boundary layer. One step beyond the black specks, will be tiny specks/***** of aluminum coming off the pistons that will be fused to white porcelain,....the next step to be reached is occasional pieces of the
porcelain being broken-off as detonation gets worse, etc. Soon after that are holes, blown head gaskets, broken connecting rods, etc.
*** Additional signs of beginning detonation are piston rings. By comparing ring's "free diameter" to "out-of-box" free diameters of new unused rings will reveal beginning of detonation before much harm is caused !!! This is a result of the above previous explanation about heat being transferred more readily because the of the relatively insulating/cooler boundary layer being disrupted by the shock-wave. A piston ring is a simple spring, when a spring is over-heated it will loose tension.
****Also on the "Center Electrode", something else to look for. The very tiny, sharply defined porcelain "ditch" that encircles the center electrode, will also show up early signs of pre-ignition or detonation as the wrong heat-range. Look for signs of the ditch beginning to fill up with melted
porcelain. You will need a 5x or 10x magnifying glass to check this.
RECOMMENDED SPARK PLUGS FOR NITROUS APPLICATIONS
FROM PERSONAL EXPERIENCE: **I like the NGK line of plugs because
they are the easiest to read. Also a good plus is the Autolite brand. They
have the hardest non-eroding electrode and will absorb more heat before
burning off.
NON RECOMMENDED SPARK PLUGS : Any resistor type spark plug.
Split Fire and Platinum spark plugs run too hot and cause "Detonation"
because they are self cleaning and run hotter then normal plugs. Stay away
from projected tip plugs with Nitrous, to much plug in the hole and easier
to lose a tip.
**When tuning a new combination, I tend to stay away from plugs that use an inconel "strap"....I like to utilize the softer steel ground strap of a "regular" plug as a fuse (it will burn off and cause a miss, rather than hurt the engine). Hope this helps....it's kinda verbose, but if you want to get it right....there are no shortcuts.
Steve
#6
02-05-2004, 07:28 PM
#7
02-05-2004, 07:43 PM
Characteristics of running lean vs. rich
n2xlr8n wrote -
What do you mean by a "full turn"?
The air/fuel mixture ratio shows up on the base ring. This is the last thread ring, it has the strap welded to it. You want a full turn of light soot color on the base ring!!! If you want to tune for maximum power, then you want 3/4 to 7/8ths of a full turn of light soot color to show up on the base ring. This is on ragged-edge of being too lean, but will make the most HP in most engines.
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#8
02-05-2004, 08:06 PM
Characteristics of running lean vs. rich
Originally posted by: NovaKaw650
n2xlr8n wrote -
What do you mean by a "full turn"?
n2xlr8n wrote -
The air/fuel mixture ratio shows up on the base ring. This is the last thread ring, it has the strap welded to it. You want a full turn of light soot color on the base ring!!! If you want to tune for maximum power, then you want 3/4 to 7/8ths of a full turn of light soot color to show up on the base ring. This is on ragged-edge of being too lean, but will make the most HP in most engines.
A full turn around the periphery of the base ring (360*). ....3/4ths of a turn is 270*, etc. [img]i/expressions/face-icon-small-smile.gif[/img]
Steve
#9
02-05-2004, 09:11 PM
Characteristics of running lean vs. rich
Why isn't the color even the whole way around? Is it darker/cooler on the intake valve side of the plug, or does it have something to do with the location of the ground strap? Sorry for the dumb questions. [img]i/expressions/face-icon-small-blush.gif[/img]
#10
02-05-2004, 09:36 PM
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Characteristics of running lean vs. rich
does this picture represent from the top down
lean
ok
rich
http://www.ngksparkplugs.com/techinf...000&country=US
lean
ok
rich
http://www.ngksparkplugs.com/techinf...000&country=US