How to Read Build Up on Spark Plugs
Information technology's best to view plugs with a 10x power illuminated magnifying type glass.
What each part of a plug signifies:
- "Ground Strap" = Oestrus Range
- "Plug's Base of operations Ring" = Jetting
- "Porcelain" = signs of pre-ignition/detonation
Heat Range
The ground strap indicates the heat range of the spark plug. If the "colour" of the ground strap "changes" too close to the ground strap'south end, (located above the center electrode), so the oestrus range is "too common cold", pregnant that the strap is loosing rut likewise apace to the base ring. Information technology is non able to burn down off deposits until near its stop.
If the "colour" of the strap changes well-nigh where information technology is welded/attach ed to the base of operations ring (terminal thread ring), and so the plug heat-range is "too hot", because oestrus is non being transferred or cooled from the strap to the base of operations ring apace enough. The strap might begin to human activity like a "glow-plug". Eventually causing pre-ignition and/or detonation subsequently. The proper heat range is when the "colour" is at the half-way betoken on the strap. This means the plug is neither too common cold or too hot.
Color: (Meaning the evidence of heat or lack of rut by the appearance nighttime vs. lightened color of metal.)
Jetting
The air/fuel mixture ratio shows up on the base band. This is the last thread ring, information technology has the strap welded to it. You want a full turn of calorie-free soot color on the base ring!!! If yous want to tune for maximum power, then you want 3/4 to 7/8ths of a full turn of light soot colour to evidence up on the base band. This is on ragged-edge of being also lean, only will brand the virtually HP in most engines. To be safe, leave it at a full turn of light soot color. If the base band has a full plough of color, simply there are "spots" of heavy build-up of "dry out soot" on top of color, and then jetting is too rich. ****If the base of operations ring has a full plough of color with some spots of heavy dry out soot, then jetting is too rich, REGARDLESS, if the porcelain is "Os-WHITE", jetting is notwithstanding Likewise RICH.****
Pre-ignition/Detonation:
The porcelain shows up pre-ignition and detonation (timing/octane). It volition non accurately reveal jetting/air/fuel ratios. To wait 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 called-for, the explosion is heard as a "metallic knock", this audible knock is the effect of a sound stupor-moving ridge, this shock wave travels back and along across the clearance book "disrupting" the libation boundary layer gases that cover the entire clearance book area. This disruption allows "more" rut to be transferred into parts, especially, domes/piston tops,...along with the very rapid rise in pressure similar a hammer accident, pistons tin can get torched with melted sides and holes !!! With the early signs of detonation, the shock-wave will besides 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 equally specks are soot that was clinging to clearance book surfaces in the relatively "even so-air" of the boundary layer. One step across the black specks, volition be tiny specks/balls of aluminum coming off the pistons that volition be fused to white porcelain,....the next step to be reached is occasional pieces of the porcelain being cleaved-off equally detonation gets worse, etc. Soon subsequently that are holes, diddled head gaskets, broken connecting rods, etc.
*** Boosted signs of beginning detonation are piston rings. Past comparing ring's "complimentary diameter" to "out-of-box" free diameters of new unused rings will reveal beginning of detonation earlier much harm is caused !!! This is a upshot of the above previous explanation nearly heat being transferred more readily because the of the relatively insulating/cooler purlieus layer existence disrupted past the shock-wave. A piston ring is a simple leap, when a spring is over-heated it volition loose tension. Too on the "Center Electrode", something else to look for. The very tiny sharply divers porcelain "ditch" that encircles the center electrode, volition also show upwardly early on signs of pre-ignition or detonation as the wrong oestrus-range. Await for signs of the ditch showtime to make full up with melted porcelain. Yous will need a 5x or 10x magnifying glass to check this.
Update: 05/02/08
Tuning With Unleaded Gasoline:
When tuning with an unleaded racing gasoline, one needs to pay a little more attention to some details than with leaded gasoline. Spark plug reading becomes more critical considering it is harder to go color on the plugs with unleaded. Getting the air/fuel ratio correct is tougher because most unleaded gasoline incorporate oxygen which adds to the oxygen in the air.
Looking at the exhaust pipes will not tell much except that there is no grayness color from the pb. How do we accomplish this chore that was previously done with the naked eyeball?
Some of this is actually tough because we go accustomed to 1 way of doing things and our earth begins to turn upside downward as fuel parameters and environmental regulations change. To commencement the process you demand a skilful light to "read" the spark plugs. It has to be a lite with a magnifying drinking glass associated with it.
There are several available on the market. They resemble the instrument that your physician sticks in your ear to accept a look at what e'er he is looking at in at that place. Peradventure for us involved in racing, he is simply checking to see if the pathway to the other ear is clear so that he can see daylight out the other side.
Spark Plug Reading:
It is always best to offset with a new prepare of plugs. When reading the plugs, always look at the entire fix, and make jet changes where they are needed. The carburetor does non have to take the aforementioned size jets in all four corners.
In fact, information technology is very unusual in a racing engine to have the aforementioned size jets in all four corners of the carburetor. This is due to differences in manifolding, inertia forces, etc.
Reading spark plugs needs to be washed with proper light / magnifying glass mentioned previously so you can see all the way down (invert the plug to read it) into the plug where the insulator (white office of the plug) comes through the steel instance. What you are looking for hither is a slight coloring on the insulator simply to a higher place the steel example. This is chosen the "fuel ring" and to accept the right air fuel ratio, the "ring " should be visible all the way around the insulator.
If it is spotty or very light, the engine either has not run long enough to develop a fuel band, or it is too lean. A visible ring that just offsets the white color of the ceramic is usually a skillful sign. In contrast, leaded racing gasoline will colour a plug much quicker than unleaded and a correct "fuel ring" will usually exist little darker due to the lead in the gasoline. To correctly read a plug with leaded gasoline, it is necessary to have the same practiced light / magnifying glass identified higher up. They are not cheap, so don't endeavour to steal 1 from your doctor's examining room.
Also the fuel band as an indication of the correct air-fuel ratio, some other indication is light shiny spots at or virtually the tip of the insulator on Autolite plugs but. These are hard to see and show up on Autolite plugs simply. It has to do with the material used in the insulator. Not all insulators are the same.
If the spark plug insulator shows whatsoever sign of small dark spots, especially at or very most the tip, detonation is taking place in that particular cylinder. Those night spots are sometimes referred to every bit "speckles" and are very small pieces of aluminum oxide that take been cooked off the top of the piston due to the abnormal temperature / pressure that occurs during detonation. One cannot afford much of this earlier failure. If this condition is observed, a conclusion must exist made as to whether the mixture is besides lean, or if at that place is too much spark timing. Keep reading, we're non there notwithstanding.
Looking at the side electrode of the plug will help to determine the correct spark timing. Ideal timing is indicated when the side electrode shows heat all the way to the case. If in that location is not an indication of rut all the mode to the side electrode / case, then spark timing should be increased. If the heat line stops 1/16th of an inch short of the side wire / case connection, the engine needs an additional 0.5o of timing.
If spark timing appears to be correct, but there are signs of detonation, the air fuel mixture is too lean. The carburetion must exist fabricated richer by going to larger jet(due south).
Detonation is unlikely to occur in all cylinders at the same fourth dimension unless the spark timing and/or the air fuel ratio is style off. Commonly detonation will show upwards in one or 2 cylinders. Richen only the corner of the carburetor(s) that feed the problem cylinders. Be certain to verify that the detonation problem has been resolved.
Jet Changes and Density Altitude (DA):
Racers apply " Density Altitude" (DA) as a measurement when tuning an engine. If, for instance the DA is 1200 feet, this means that the air at that racetrack has a density equal to what air would be at 1200 feet above body of water level if standard conditions exist at sea level. Equally the DA increases at that place is less oxygen available, and the mixture needs to be leaner. For every 750 feet that DA increases, the jet size needs to be reduced by one size.
In contrast, for every 750 feet that DA goes downwards, jet size needs to be increased by 1 size.
Air Fuel Ratio:
In the "old" days, all that we had to be concerned with is getting the correct amount of oxygen from the air mixed with the correct corporeality of gasoline being used. In tuning with unleaded gasoline, we also demand to take into account the amount of oxygen in the gasoline (if there is any). This function can become critical.
Let's presume that a racer has his engine "dialed in" on Rockett Brand TM 111 Leaded Racing Gasoline and his sanctioning body is switching to Rockett Brand TM 100 Unleaded Racing Gasoline. The 111 has a specific gravity (SG) of 0.721, and the 100 has a SG of 0.744. Normally when changing from a gasoline with a lower SG to ane with a higher SG, one must lean the mixture past going to smaller jets in the carburetor. In this case it would exist virtually ii jet sizes in a Holley carburetor. That is not the right movement in this example because the unleaded contains two.7% oxygen which in this instance will negate the jet change. The engine may like richer jets than it did with the 111, but the jets used with the 111 are a good identify to brainstorm.
Just try to remember, "When in doubt, go richer". This can reduce the need to build (or buy) a new engine.
The above example is why it is disquisitional to know how much oxygen is contained in the unleaded gasoline used. This is also the same reason that racing with street gasoline is non a good idea since one never knows how much oxygen is contained in the street gasoline.
Know your racing gasoline, know your racing gasoline supplier, know if it contains oxygen, and if so, how much? Don't depend on data from your buddies. Call your supplier (does this audio bad or what) and if he doesn't know, change suppliers.
Frazzle Pipes:
Using an unleaded gasoline volition not colour a pipe to the gray that we saw with leaded gasoline, so don't look for information technology. Exhaust pipes used with unleaded gasoline will be slightly black in contrast to the gray that was observed with leaded gasoline.
Experience:
All of this takes feel. The more than y'all do it, the easier it will get. Accept your time, pay attention to details, and everything volition come up together.
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 accept the hardest not-eroding electrode and will absorb more heat before called-for off.
NON RECOMMENDED SPARK PLUGS:
Whatever resistor type spark plug. Divide Fire and Platinum spark plugs run as well hot and cause "Detonation" because they are self cleaning and run hotter so normal plugs. Stay away from projected tip plugs with Nitrous, to much plug in the pigsty and easier to lose a tip.
How to Read Build Up on Spark Plugs
Source: https://www.sites.google.com/site/kensautomachineshop/technical-information/articles-and-tips/tips---reading-spark-plugs
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