Spark Plugs

[Torch_Red_04]

I just read in a Mustang magazine (5.0?) about bolt ons for Cobras. Pulley, tune, cat back and cold air. When they changed the pulley they removed the factory platinum spark plugs and replaced with regular plugs. They claimed the platinum tips are more knock sensitive. Anyone have any feedback on this? We could prove this out with a scan tool while driving to see if the timing was being retarded based on knock sensor input I guess.

[sonicblue03]

I can only say from my experience.
my signature has all my upgrades
Car runs great, no knocking or any other performance problems.
17K, 6 track events and still have original stock plugs

[JRHWhiteSnake '04]

Knock sensitive?
WTF?

You mean more likely to produce knock for a given condition
than regular plugs? (resistor or non-resistor types?)

I'm sure that plug gap and indexing (or lack of it) had more to do with it.

[Torch_Red_04]

I did more research on this because it sounded like magazine editor BS. Turns out the platinum electrode is not as good a conductor of heat as the old steel electrode. HOWEVER when OE selects the plug they know this and use the appropriate heat range. This started with guys putting blowers on non boosted cars and getting detonation caused by a hot plug tip in the chamber. Go to the same plug in a steel electrode and it runs a little cooler and no knock. Basic hot rod science - when you up the ante you need to watch the plug temperature regardless of the type of plug or engine. Just BS on our cars however.

[EbloomPonycar]

I just had my pulley changed to a 2.81 with an idler. SCT Custom tune at PAS. Dynoed at 415 rwhp and 448 rwtq. Not bad numbers considering stock airbox with K&N filter and a cat back fr500 exhaust. We did have to change out the plugs as it would break up at about 4000. Changed the stock plugs with stock autolites and gapped at .030. down from .042. The orginal plugs looked ok. Immediately fixed the problem. I had a similar problem with some platnium plugs on a 1993 fox with a 9lb powerdyne. Would break up around 4000. Changed plugs and gapped down to .035 and the problem was solved.

[ausie]

Most (if not all) platinum plugs are platinum tipped. The center core is made of a copper alloy which acts as a good thermal conductor as well as a good electrical conductor. Most standard plugs are nickel plated copper. If the center electrode was made of steel it would retain heat much longer than the nickel copper alloy or the platinum tip. The only benefit of platinum is that it is a harder metal than copper or nickel and it is less reactive to the combustion byproducts than the two mentals commonly used. The stock plug in the 04 cobra is an improvement over the larger electrod used in the 01's but has a much colder heat range (one heat range colder than that used in the 03 model year). What I found that makes a difference is the Irriduim plugs (Denso or NGK) when gapped at 0.030 to 0.035.

[EbloomPonycar]

For some reason on normal street driven cars I thought the gap was the main issue here. The larger spark gap was being blown out by the high boost pressure. The spark energy is much higher than cars of not so long ago. I did not know the 04 plug was a little cooler than the 03. Shouldn't you run the coolest plug you can get away with? My belief also was that the change in plug material was just so the electrode would not deteriorate. In the old days it was not uncommon to see copper based electrode deterioration after 12 or 15k.

[ausie]

For some reason on normal street driven cars I thought the gap was the main issue here. The larger spark gap was being blown out by the high boost pressure. The spark energy is much higher than cars of not so long ago. I did not know the 04 plug was a little cooler than the 03. Shouldn't you run the coolest plug you can get away with? My belief also was that the change in plug material was just so the electrode would not deteriorate. In the old days it was not uncommon to see copper based electrode deterioration after 12 or 15k.

Electrode erosion is the main reason for the different alloys used in the spark plugs. The stock plug used on an 04 is AGSF 22FM1 Not quite sure of the stock part number for the 03 but if it is AGSF 20FM1 or similar number, the higher number (22) is one heat range colder. I have cross referenced plugs in the denso web site and noticed that the 03 (IT20) has a hotter plug than the 04 (IT22). The electrode design also plays an important role in spark energy distribution over the surface area as well as at what voltage the plug will fire. You are exactly right about the spark gap and plasma blow out with higher boost. Being able to reduce the gap without resulting in a weak spark is also important. Some plugs have fine wire or reduced surface area of the electrode tip which improves charge density as well as offer a slight timming advance when the spark plug fires.

[EbloomPonycar]

I will have to pull one and see what is in there. Maybe I will put the denso's in and spread the gap to .35 instead of .30. I guess the more gap the better as long as nothing else is affected. Is there a model or type associated with the denso plug? I have never used them.

[ausie]

For a stock or mildly modded motor the Denso plug for the 04 is IT22. NGK also has a similar plug desing. Actually they have two.

ITR6F-13 (look more like the oem stock plug) average cost per plug $11.99
TR6IX (more like the denso plug) average cost per plug $7.99

The denso plug IT22 cost about $11.99 per plug.

The required gap on the denso is 0.044 but I have mine gapped to 0.034. Use extreme care when gapping iridium plugs as it is easy to snap off the iridium tip also not to touch the ceramic insulator as well. The difference between the Denso and the NGK is that denso has a 0.005" groove cut in the back of the ground ****g. Remember this: the surface area of the center electrode if large would require a wider gap since the charge density is lower than that of a plug with a narrow tip. The gap itself basically sets the voltage potential of the spark. It takes a higher voltage to bridge the gap if it is set wider. The stock Ford plug does have a narrow tip (not the same plug that you would pull out of a 99/01 Cobra). A 0.035" to 0.040" gap may be more applicable with the stock plug than the 0.030" unless you are running more boost, you may need a colder plug. The typical tolerance of setting the spark gap is around 0.008" and as long as you are within that tolerance you should be fine. As for the stock plug it may have a different tolerance in offset from nominal as compared to the iridium plug. I have read in other forums that many are using an 0.030" gap with the NGK or Denso's with higher boost levels without any problems. Best to talk it over with your tuner if you have one to make sure you set the gap in the proper range as well as get the right plug for your application.

[EbloomPonycar]

At $12 a plug maybe I will leave them alone. I am not currently experiencing any problem. I am running a 2.81 pulley so there is a little more boost there. Maybe I will pull the plugs and go with a .035 gap instead of the .030 just to see where the limit is. I am going to spend the money on a MM strut tower brace instead. Maybe add a set of full length subs as well.

[ausie]

Since you are running more boost, and if you are not having any issues with the 0.030" gap I would just leave it at that. There are associated issues with increase boost or high compression ratios that would probably require a smaller gap to prevent the spark from blow out.

The iridium plugs are not cheap by any means. Before you make any mods such as spark plugs, best to research the topic before you decide to make the change.

[EbloomPonycar]

Shouldn't I push the envelope to see what the greatest gap is that I can run before blowout. That would give me the greatest spark energy correct? I am not having detonation problems so I am not sure the cooler plug would make any difference unless I started to push the timing a little bit to see if there was a limit for each type of plug. I have the SCT tuner, what I really want to do is start tweaking things a little at a time to see if I can pull a little more out of her. Dangerous if not done on a dyno but should not cause any serious harm since I am not racing in any form at this time.

[ausie]

I would not go beyond the recommended spark gap of 0.046 since the spark energy will take longer to build up before the gap is breached with the plasma or arc. Too much of a gap would hinder the top end and may cause a miss-fire. Also this may lead to a hot spot on the ground ****g since it will begin to get burned away if the spark energy is too high. The timming will not change by much with spark gap adjustments but there is some transient time response since the spark gap acts like a capacitance which holds a voltage potential up until the point the voltage exceeds the brake over creapage distance. Creapage distance is the effective distance between two conductors of opposite polarity that would prevent arcing. Considering that the spark energy is in excess of 5k to 10k volts. I would probably just set the stock plug to about 0.035 5o 0.040 and leave it at that. In order to gain more advance timming, it would be more critical to reduce compressor heat of the air charge by means of a more efficient heat exchanger to improve the safety margine (less ****e to detonation). There is alot of information that can be found on the NGK website as well as the denso site, along with more information in the Kenn Bell site. It is interesting to note that after studying ESD (electro static discharge) issues with printed circtuit board designs and natural gas igniters,,, etc... I have learned many things in relation to the firing tip of spark plugs, how the shape of the tip does matter. The smaller and sharper the tip the higher the current density of the spark. After my first experience with the injection type tip on an ESD tester I noticed a large difference in discharge engergy as well as a higher voltage potential when compared to the air gap tip which is rounded and broad in diameter. The same applies to spark plugs.

[RevMatt]

I would not go beyond the recommended spark gap of 0.046 since the spark energy will take longer to build up before the gap is breached with the plasma or arc. Too much of a gap would hinder the top end and may cause a miss-fire. Also this may lead to a hot spot on the ground ****g since it will begin to get burned away if the spark energy is too high. The timming will not change by much with spark gap adjustments but there is some transient time response since the spark gap acts like a capacitance which holds a voltage potential up until the point the voltage exceeds the brake over creapage distance. Creapage distance is the effective distance between two conductors of opposite polarity that would prevent arcing. Considering that the spark energy is in excess of 5k to 10k volts. I would probably just set the stock plug to about 0.035 5o 0.040 and leave it at that. In order to gain more advance timming, it would be more critical to reduce compressor heat of the air charge by means of a more efficient heat exchanger to improve the safety margine (less ****e to detonation). There is alot of information that can be found on the NGK website as well as the denso site, along with more information in the Kenn Bell site. It is interesting to note that after studying ESD (electro static discharge) issues with printed circtuit board designs and natural gas igniters,,, etc... I have learned many things in relation to the firing tip of spark plugs, how the shape of the tip does matter. The smaller and sharper the tip the higher the current density of the spark. After my first experience with the injection type tip on an ESD tester I noticed a large difference in discharge engergy as well as a higher voltage potential when compared to the air gap tip which is rounded and broad in diameter. The same applies to spark plugs.
:cbra:
With very few mods and 99% street use, the best plugs are___ with a gap of ____ ?! please see my mods list. :huh:
thanks!

[ausie]

I would recommend Denso IT22 gapped at 0.034 (there is a 0.005" notch in the ground ****g so the total effective gap would be 0.039) or you can leave the plug as is with total gap of 0.045 (0.040 between center electrode and ground).

There is also the NGK plug TR6IX and use the same gap (0.040 to 0.035). If you do gap the iridium plug be extremely carefull not to touch the center electrode or ceramic insulator. Only check the gap with a feeler guage (not the round metal loop guage).

If you decide to keep the stock ford plug, you can drop the gap down to 0.040" which is 0.004" shorter than the minimum specified gap.

[EbloomPonycar]

I have new stock Ford plugs gapped at .030. Maybe I will increase to .040. On the dyno with the original stock plugs and the 2.8 pulley it was breaking up at 4000. Changed the plugs and gapped to .030 with no problem. The wider gap must help combustion somewhat.

[ausie]

The wider the gap, the higher the voltage charge must be to breech the gap. It is a factor of the electrode surface area and the distance it must travel to discharge. 0.044" to 0.046" is the recommended gap which is listed on the emmisions label under the hood. Having the miss fire or sputter at 4000 rpm is not good since that will cause harmonic disturbances. The reason why the 0.030" improved the operation of the motor at that RPM or above is that the Forced induction is working against you when it blows out the plasma of the arc. You do not want to close the gap too much as that will drop the effective voltage of the discharge energy. The stock plug is a good plug but the Denso or NGK iridium plugs provide a much smaller electrode that will create a higher charge density at the tip. Another key point about the tip is the sharp edges. Discharge energy can be hot enough to burn through the ground ****g and over time it will become eroded. Not to mention the effects of contaminants or byproducts of combustion forming on the metal surfaces which may interfer with the discharge path. Also the ground ****g shape as well as the electrode shape are important factors in providing a good flame kernel. If I had known that the NGK TR6Ix cost less than the Denso IT22 plug I would have bought them. Since I have used Denso in the past in my 01 and was pleased with the performance I got the same plug but different heat range for the 04. There may be a slight sputter on rare occasions at low RPM when cruisng but it is far less than what I got with the stock plugs. There are alot of other factors that may cause issues with combustion, for instance; how much motor oil is finding its way into the intake.... That will lead to issues down the road if left unchecked. How did your plugs look after you pulled them?

[EbloomPonycar]

Plugs looked good. Only 5k on them. A little red hue which was odd. The car sat on the dealer showroom for the first year of its life. Maybe they used some STA-BIL in the gas. Sputtering only occurred under full throttle run on dyno at about 4k. Fine after plug change and gap to .030. No problems since. I also put an oil seperator in last week. Seems to take some oil out of the PCV stream that is for sure. Eibach 3594.140 springs last night (Fronts) + MM CC Plates. Rear springs this weekend. Hopefully some winding roads in the near future.

[RevMatt]

The wider the gap, the higher the voltage charge must be to breech the gap. It is a factor of the electrode surface area and the distance it must travel to discharge. 0.044" to 0.046" is the recommended gap which is listed on the emmisions label under the hood. Having the miss fire or sputter at 4000 rpm is not good since that will cause harmonic disturbances. The reason why the 0.030" improved the operation of the motor at that RPM or above is that the Forced induction is working against you when it blows out the plasma of the arc. You do not want to close the gap too much as that will drop the effective voltage of the discharge energy. The stock plug is a good plug but the Denso or NGK iridium plugs provide a much smaller electrode that will create a higher charge density at the tip. Another key point about the tip is the sharp edges. Discharge energy can be hot enough to burn through the ground ****g and over time it will become eroded. Not to mention the effects of contaminants or byproducts of combustion forming on the metal surfaces which may interfer with the discharge path. Also the ground ****g shape as well as the electrode shape are important factors in providing a good flame kernel. If I had known that the NGK TR6Ix cost less than the Denso IT22 plug I would have bought them. Since I have used Denso in the past in my 01 and was pleased with the performance I got the same plug but different heat range for the 04. There may be a slight sputter on rare occasions at low RPM when cruisng but it is far less than what I got with the stock plugs. There are alot of other factors that may cause issues with combustion, for instance; how much motor oil is finding its way into the intake.... That will lead to issues down the road if left unchecked. How did your plugs look after you pulled them?

:spinem: I am a relative "newby" to the Mustang performance and mod game. I appreciate the clear info that your post provided! Thanks!
:beer:

[ausie]

funny, the word p r o n g was a bad word..... replace the ****g with ground "arm", "strap", if they come up with **** then try the "metal arm that extends from the threaded body of the spark plug to where the arc of the spark makes the ground connection.


:bash: there was nothing offensive in that post and why such a word is taboo is beyond me. :huh:

I have studied this for some time since it is my job to understand how gas igniters work and what they do to the power supply and electronics that control them, ESD (electro static discharge) injection or air gap, fly-back converters, relays (coils) and related items. After getting some knowledge on the toppic of ESD I found it does relate to spark plugs used in engines. It will take about 17kv to spark across a 0.250" gap. Based on what I have seen in the field of engineering, typical spark gaps of 0.040 would require much less than 5kv to breech. A charged coil once disconnected abruptly can generate 100 to 1000 times the applied voltage. This is termed inductive kick back.

There is also alot of information in the web sites of many spark plug manufacturers (some is good and some is sort of lacking any relavant info).

[EbloomPonycar]

I was wondering what all that **** was about.

[ausie]

I guess I learned a new bad word.... :rolleyes: I will have to look it up and see if there is a slang use for it..... p r o n g :kiss: :cool:

[DARKDAYZ]

i am running the 2.8 pulley and jlt cold air we put ngk 1 step colder plugs in it and sct2 programmer and we closed the gap a little bit down to 35 runs great so far ....just my 2 cents worth.....

[EbloomPonycar]

I guess I will open mine up from .030 to .035 to see what happens.

[gcassidy]

Greg, correct me if I'm wrong.

It's P R O N that is causing ****. I've seen it elsewhere. It's too close to
P O R N. :huh:

[RevMatt]

i am running the 2.8 pulley and jlt cold air we put ngk 1 step colder plugs in it and sct2 programmer and we closed the gap a little bit down to 35 runs great so far ....just my 2 cents worth.....

my local Ford dealer "warned me" against changing the plugs lest I hurt the cylinder? He then tried to sell me some BS about repolarizing new plugs if I install them. Is he as full of c_ap as I think he is?
:upst: