A thread for reading spark plugs

[red1993gsallmt]

I really think it would be a good idea to have a thread about reading plugs for tuning. Last night I was helping a friend tune a bbc with a aem wideband but had a gut feeling the car was lean even though the wideband was saying other words, sure enough we may have saved his motor just by old fashion plug reading. Im not good with pics but maybe someone has a good pic of a plug from a well tuned car so we can show others what parts of the plug show you timing, a/f, heat range, detonation, etc. Todays sensors are great but plugs never lie.

 

[ktgurl87]

Like they have on the last page of the Haynes manuals? It shows the different tips of spark plugs to show you what your car is doing. Tis pretty nifty.

 

[Pipnorcali]

Pics here


http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp

Home » Tech Support » Spark Plugs » Faqs
FAQs - Spark Plugs

Q: How do I "read" a spark plug?

A: Being able to "read" a spark plug can be a valuable tuning aid. By examining the insulator firing nose color, an experienced engine tuner can determine a great deal about the engine's overall operating condition.

In general, a light tan/gray color tells you that the spark plug is operating at optimum temperature and that the engine is in good condition. Dark coloring, such as heavy black wet or dry deposits can indicate an overly-rich condition, too cold a heat range spark plug, a possible vacuum leak, low compression, overly retarded timing or too large a plug gap.

If the deposits are wet, it can be an indication of a breached head gasket, poor oil control from ring or valvetrain problems or an extremely rich condition - depending on the nature of the liquid present at the firing tip.

Signs of fouling or excessive heat must be traced quickly to prevent further deterioration of performance and possible engine damage.


Normal Condition
An engine's condition can be judged by the appearance of the spark plug's firing end. If the firing end of a spark plug is brown or light gray, the condition can be judged to be good and the spark plug is functioning optimally.

Dry and Wet Fouling
Although there are many different cases, if the insulation resistance between the center electrode and the shell is over 10 ohms, the engine can be started normally. If the insulation resistance drops to 0 ohms, the firing end is fouled by either wet or dry carbon.

Overheating
When a spark plug overheats, deposits that have accumulated on the insulator tip melt and give the insulator tip a glazed or glossy appearance.

Deposits
The accumulation of deposits on the firing end is influenced by oil leakage, fuel quality and the engine's operating duration.

Lead Fouling
Lead fouling usually appears as yellowish brown deposits on the insulator nose. This can not be detected by a resitsance tester at room temperature. Lead compounds combine at different temperatures. Those formed at 370-470°C (700-790°F) having the greatest influence on lead resistance.

Breakage
Breakage is usually caused by thermal expansion and thermal shock due to sudden heating or cooling.

Normal Life
A worn spark plug not only wastes fuel but also strains the whole ignition system because the expanded gap (due to erosion) requires higher voltages. Normal rates of gap growth are as follows:
Four Stroke Engines: 0.01~0.02 mm/1,000 km (0.00063~0.000126 inches/1,000 miles)
Two Stroke Engines: 0.02~0.04 mm/1,000 km (0.000126~0.00252 inches/1,000 miles)

Abnormal Erosion
Abnormal electrode erosion is caused by the effects of corrosion, oxidation and reaction with lead - all resulting in abnormal gap growth.

Melting
Melting is caused by overheating. Mostly, the electrode surface is rather lustrous and uneven. The melting point of nickel alloy is 1,200~1,300°C (2,200~2,400°F).

Erosion, Corrosion and Oxidation
The material of the electrodes has oxidized, and when the oxidation is heavy it will be green on the surface. The surface of the electrodes are also fretted and rough.

Lead Erosion
Lead erosion is caused by lead compounds in the gasoline which react chemically with the material of the electrodes (nickel alloy) as high temperatures; crystal of nickel alloy fall off because of the lead compounds permeating and seperating the grain boundary of the nickel alloy. Typical lead erosion causes the surface of the ground electrode to become thinner, and the tip of the electrode looks as if it has been chipped.
Examples of common problems that effect the firing nose of the plug >

 

[Mr PopUps]

Or you could post a pic (dont remember where/when i got it, but it was a loooooong time ago)

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[DeadlyScone]

Reading and Selecting Spark Plugs

Heat range pic

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Do I Need To Use A Resistor Plug?
Today's spark plugs use resistors to eliminate radio frequency interference (RFI) which can affect on-board computer or ignition systems, AM and FM radio reception, and TV broadcasts. Each time the spark jumps across a gap, an electromagnetic field is created that can interfere with radio signals. By placing a resistor in the spark plug, we can substantially reduce RFI. Furthermore, the use of non-resistor plugs with today's complex computer systems can result in driveability problems, loss of performance and can even cause the computer to store trouble codes.


How Does Heat Range Affect A Plug?
As discussed, a spark plug is made up of ceramics, steels and nickel alloys. These materials do not have the ability to produce energy or heat. When we talk about the heat range of a spark plug, we're referring to its ability to move heat away from its tip or core nose into the cooling system. A cold spark plug would have a cooler tip temperature than a hot one. With today's fuels, we know that anytime the tip of the ceramic core nose goes below 850 F, carbon will build up and the spark plug will foul. We also know that if the tip temperature of the plug exceeds 1550', the metals will begin to break down. At approximately 1700, the plug will glow and can become a source of pre-ignition within the combustion chamber. Armed with this information, it becomes clear that maximum performance can be achieved with a spark plug that has a temperature of greater than 850 at idle, but no more than 1550' under wide open throttle.


Installation Tips
Here are a couple of tips to help assure the success of changing spark plugs. The first is to remove spark plugs from aluminum cylinder heads only when the engine is cool. Since aluminum and steel expand and contract at different rates, removing spark plugs from an aluminum cylinder head while hot can actually cause thread and cylinder head damage. Before installing the spark plugs, make sure the threads are clean and in good condition. If in doubt, run a thread chaser through the plug opening in the cylinder head. Most plug manufacturers recommend that you do not use an anti-seize compound, since one has already been applied to the plugs at the factory. Next, install the spark plugs finger tight and, it using a taper seat spark plug, use a ratchet to rotate 1/16 of a turn. If using a gasket seat type spark plug, after installing finger tight, turn 1/4 to 5/8 of a turn. If this procedure is followed, spark plugs will not back out nor will they seize in the cylinder head.


Reading the Plugs
We have provided a list of firing end conditions to help you identify situations that may occur in your vehicle. It is helpful to use a magnifying glass to view these deposits. We recommends the use of a 5 power magnifier with a light that will allow you to see small deposits on the corners of the spark plug and make an accurate diagnosis.


Normal Firing End
A grayish tan to while color indicates the correct heat range spark plug is in use, the fuel and ignition systems are in good shape and overall engine mechanical condition is good. Replace with new plugs of the same heat range. Refer to the owner's manual for recommended spark plug change interval.

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Worn Out
Worn or rounded center and/or ground electrodes indicate excessive wear and can cause misfire during acceleration, hard starting or reduced fuel economy and damage to other secondary ignition components e.g., spark plug wires, coils and distributor cap with continuous use. When a plug has this type of appearance, it has simply exceeded its useful life. Replace with new spark plugs of the same heat range and design.

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Detonation
In cases of light detonation, small black or gray spots will be noticed on the core nose of the spark plug. In cases of severe detonation, insulators may be cracked and/or chipped. The same high pressure waves created during detonation can break spark plugs, damage intake valves and break pistons. Make sure that the correct octane fuel is being used, assure proper operation of emission and computer systems, and assure the correct heat range of spark plug is being used.

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Mechanical Damage
Bent and/or broken electrodes and core nose indicate mechanical damage caused by foreign objects in the combustion chamber or improper reach spark plugs, Remove the foreign object from the engine and check the owner's manual for proper spark plug application.

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Overheated
Chalky white insulator with little or no coloration, accelerated electrode wear and possibly blistered or pitted electrodes are indications that a plug has overheated. The shell may also be discolored from light gray to a dark blue, almost black. Check for the correct heat range spark plug. Verify that ignition liming and air fuel mixtures are adequate. Engine overheating and restricted exhaust systems can also cause this condition.

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Ash Deposits
Light brown deposits encrusted on the ground and/or center electrodes indicate ash deposits. This situation is caused by oil and/or fuel additives. When the deposits are found on only one side of the spark plug core nose, it is usually considered to be a problem with the cylinder head (valve stem seals or valve guides). When they are found on both sides of the spark plug, it is often considered to be a problem sealing at the piston rings. This condition can mask the spark and, in some cases, contribute to misfire. Check for worn valve guides and valve stem seals and/or piston rings. The spark plug is the correct heat range and was a victim of the engine's condition, not the cause of it. We does not recommend the use of fuel additives which leave deposits on the core nose of the spark plug.

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Oil Fouled
Symptoms of oil fouling include black oily coating caused by poor oil control. This situation is more severe than what is seen with the ash-fouled spark plugs and usually represents advanced engine wear. When the oil enters the combustion chamber and covers the core nose of the spark plug, the spark no longer arcs across the gap. Rather it takes the easier path to ground by tracking down the oil on the core nose. This results in a complete cylinder misfire condition. Check for worn valve guides, valve stem seals and/or piston rings. Replacing the spark plug may help for a short time, but the new plug will soon foul.

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Initial Pre-Ignition
Signs of the spark plug being hot or blistered and/or melted center and ground electrodes are indications of initial preignition. Check that the correct heat range spark plug is being used, assure ignition timing and air fuel mixture are appropriate, assure entire ignition system is functional and check its specifications. Routing of spark plug wires on some engines can contribute to cross induction which will lead to pre-ignition. Excessive carbon deposits in the combustion chamber may contribute as well.

Sustained Pre-Ignition
Melted center and/or ground electrodes and/or a melted insulator are symptoms of sustained pre-ignition. See initial preignition, description above. Also expect to find damage to the pistons and/or exhaust valves.

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Splash Deposits
Small islands of contaminants on the insulator indicate splash deposits. Replace with new plugs of the correct heat range. The use of fuel additives, carburetor and choke cleaners or other aggressive solvents before installing new plugs is the most common cause of this condition.

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Carbon Fouled
Soft, black, sooty, dry-looking deposits indicate a rich air fuel mixture, weak ignition or wrong heat range spark plug (too cold). These carbon-based deposits are conductive, much like oil fouling, and will allow the voltage coming out of the center electrode of the spark plug to track down the core nose rather than jumping the gap. This will result in an engine misfire and further aggravate the carbon fouled condition. Check for correct plug heat range. On fuel injected engines, check for sticking injectors, malfunctioning cold start valves and/or circuits. Also check for correct fuel pressure specifications. On computer controlled vehicles, the "limp home" computer mode will always result in a rich condition. Therefore, it is imperative that you check the operation and condition of the on-board computer system. On carbureted vehicles, check choke and choke pulloff, high float level, and needle and seat condition. On all engines, severe vacuum leaks can decrease manifold vacuum, resulting in a rich condition. Weak and/or damaged secondary ignition systems will fail to spark across the gap lowering combustion chamber temperatures and promoting carbon deposits. This condition could also result from continuous low speed driving or poor cylinder compression.

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Fuel Additives
Red to purple deposits on one side of the core nose are an indication of a fuel additive. While many of these deposits are non-conductive and do not contribute to lack of performance, some fuel additives contain octane boosters that leave conductive deposits on the core nose. Care should be taken to select fuel additives which are compatible with ignition systems and do not contain conductive materials such as octane boosters.

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Exerts Copyright© 1998 Cooper Automotive (Champion Spark Plug)

 

[red1993gsallmt]

That stuff is for briggs and straton lawn motors, but thanx. Im talking more how to tune off of doing a pass and shutting down the motor and reading the plug. Like reading porcline for timing wot a/f, and detonation, ground strap for heat range and also timing. Also the base of the plug can help with tunig at an idle if you have a set of big cams with a short exhaust, Ive noticed widebands don't like to work at idle to well with a set up like that. Im talking about putting a brand new plug with one pass on it under a microscope to see if timing to high or low for peak power. Old school guys are really good at this but the new school guys are the ones with the fancy camaras to take the pics im looking for. Stuff like this guy is trying to sell. Spark Plug Reading Secrets

 

[tron2119]

That link is pretty interesting. I too would like a page for this. I think this could help A LOT of dsm'ers out.

 

[DeadlyScone]

that info was from this thread http://www.dsmtuners.com/forums/frequently-answered-dsm-questions/233421-spark-plug-faq.html
there is also some more good info on there.

 

[donniekak]

People who run alcohol fuels in their cars should read plugs during tuning. On my talon I built to run e85 I had much more success tuning off of plugs, than a wideband, and knock sensor. After I was done tuning, I just took note of what my wideband was reading, and aimed to keep it where it ended up after a couple runs reading plugs.

 

[arrowhead]

Well since I am very old school, and have a couple of friends I have been helping out, I am still leery on sensor tuning instead of plug reading and so much depends on the type of racing, that there are too many variables for me to trust the gauge readings.

You can run a 1/4 mile car a lot leaner than any other type of racing, be it boats or cars.
Very difficult to get a reading on only a few seconds in a pass, not enough time to get a proper reading or coloring, I have always advice start extra rich and work down until you get that nice tan or grey color as this will also change depending on the additives the fuel has.

All pictures above are a good starting point and a plug does not know whether it is on a lawn mower or a 16 cyl motor.

Champion spark plugs have a very nice pictorial in their catalogs.

You should also have color on at least 3 threads up from tip of plug, again depending on heat range and fuel the color will change.
Go rich first and be safe.
There is a lot to plug reading,
arrowhead

 

[ElectronVTEC]

I had heard it was two threads should be black, that indicates you're in the right heat range. If it's one, go hotter, if it's three, go colder. That could very well be wrong, but good info nonetheless. The other piece to consider is to get your timing mark right at the bend. If your mark is before the bend, you can add a little timing (obv. in 1* increments). If the mark extends past the bend, you need to pull some timing. Those two things, plus shooting for a tan coloring are all I've really looked at.

 

[arrowhead]

I had heard it was two threads should be black, that indicates you're in the right heat range. If it's one, go hotter, if it's three, go colder. That could very well be wrong, but good info nonetheless. The other piece to consider is to get your timing mark right at the bend. If your mark is before the bend, you can add a little timing (obv. in 1* increments). If the mark extends past the bend, you need to pull some timing. Those two things, plus shooting for a tan coloring are all I've really looked at.

Well do some more reading and dont go by hearsay, I personally have never heard of your mentioned procedure for reading plugs or proper tuning and I would not followed it.

I would run away from your advisors that are telling you that that is good info.