Iridium NGK Plugs

[Col-GTSX]

It seems as though most of us have had problems with miss firing at or above 7psi once iridium plugs have been installed.

I noticed after searching many threads that people are using 7/6's as their plug temp. I had a very long chat with the NGK sales rep and he said you should use 5's in an rb20/25 motor. I did and had no trouble, however with my new line R33 i am getting miss firing above 8psi.... Runs like a little beatch... I have to say i didnt gap them as it started raining as i put them in so i was in a rush.

Do you think the standard gap out of the box is too large and the boost is blowing out the spark??? I believe this to be the case. But i write this wondering who told you to run 7/6's and not 5's????

Autobarn said 5's are the most popular iridium they sell by far. Any ideas guys???

So did most of you find the gap to be the problem???

This is a thread explaining the same issue...

http://www.skylinesaustralia.com/forums/sh...t=blowing+spark

[R33S2]

I had the same problem with miss fire, and took my car back as Hardcore had just tuned it for more boost. Pete said that my plugs were the poblem and let me help him put newbies in, he gapped each one and I noticed that each plug was different with the gapping process (some were smaller others bigger) could of done it myself but was late in the day and still had to dyno again.

[Col-GTSX]

I just checked the ngk website.... You can do a search for the right plugs for you and i found this...

Your Vehicle:

1993.8 - 1998.5 NISSAN SKYLINE 2500 TURBO RB25DET

Spark Plug Part No.

Recommended Plug PFR5G-11

Iridium Option BKR5EIX-11

The iridium plugs listed there are the ones a bought and had suggested as the best in my post above.... Any thoughts guys... After reading more posts. I think gapping the plugs is the answer or upgrading to splitfire coil packs.... Gapping is cheaper... LOL

[Col-GTSX]

I just found this handy picture as well from their website...

This shows how much energy is needed at what gap on what plug....

[Col-GTSX]

Ok, regapped the plugs to 0.8mm (well as close to this point as possible).

Car certainlly ran better, however it still has a slight miss at about 6000rpm to 7000rpm...

Ill pull em out again and re-gap them to 0.7 and try again i guess....

Its funny that NGK-R plugs at 4 bucks each dont have these problems....

[Bobjones]

I am running the above plugs, at the 1.1 gap on stock boost.

I have been told that when raising the boost, I should be running copper plugs at 0.8

I think the issue may in fact NOT be the plugs as the 0.8 has also been recommended on the Iridiums many times for boost above stock. I have seen RB's running about 15-20psi with plug gaps of 0.8mm

I would be looking at the coil packs unfortunatly to isolate the problem. It may in fact be ONE of the packs not all...

[bless_you]

to be honesty... im going with bob... people are constantly talking about gapping to reduce the blow out fo the spark, when your combustion cycle is just getting less effective.

Your Coils are the most integral part of the process. i am running 6xcoils on a custom rail and running them at 1.1 gap on a 7heat range with 14lb boost and havenever had a hicup since... its the most overlooked part of the system.

Besides the skyline ignitor/coil pack srtup was weak from day 1 if you are planning on increasing the boost/power of the engine.

just my rant

[blind_elk]

Now running Iridiums (5s) in my RB25DET at 1.1 gap. Engine starts better, and has not suffered a misfire, even running 10psi boost. Running with the "in-built igniter" coils, fired by Wolf 3D.

If the system can't maintain the spark at the recommended gap, then it is likely a problem with the coils themselves, not the plugs or the boost or the fuel or...

[bless_you]

^^well said greg^^

[Col-GTSX]

The S2 R33 has the inbuilt ignightors. Yes true thats what i have also.

I re-gapped the plugs to .8 properly with feeler gadges this time and took for a run and what a dream. Problem solved, You see the iridium tip is much smaller than copper plugs. Thus causing a limited firing area. The standard coils were never designed with iridium plugs in mind. The only solution is to re-gap to 0.8mm or to purchase splitfire coils.

Re-gapping will reduce the sparks intencity however only take an hour or so. As if you purchase splitfire coils its gonna be 30 minutes labour but $650 for the coils... LOL

I had a set of splitfire's in my old line and did notice a smoother more consistent combustion. However look at the hp gains and tell me that $650 is well spent. Yes there is a certain point where you need to go and get a set. But for most of us its a part that is just not needed.

I would like to ad that the coil packs are perfect. Have run them on the test bench at work to beyond expected limitations and their all fine. Greg i aggree with what your saying there. However this is not the case on this one. I decided to run a plug on a testing machine. I dialed in the power output an rb25 (in-built ignighter) is capable of.

1st test at 1.1mm

2nd test at 1mm

3rd test 0.9mm

4th test 0.8mm

5th test 0.7mm

I will start by saying this plug used in tests had to be thrown out as when i tryed to re-open the gap the tip broke due to many changes in the gap. I will start by saying at 1.1mm the plug performed perfectlly however at a simulation on 13,000rpm the plug started to fail. On the other end of the scale at 0.7mm the plug started to fail at 16,000rpm.....

Dial up to the output of a sliptfire and the results were much better. The size of the spark and intencity was amazing and the plug didnt fail at all at 1.1mm (the test machine can only go so fast)

Testing 1.1mm at 13000rpm and failing in a controled enviroment could be the same as 5000rpm in a skyline with 150C+ temps around the plug with 10psi of boost inside the chamber... The smaller the gap the higher the plug will go (in test conditions) and id dare to say the longer it will last.

So in summary the way to solve this problem as tested is 1 of 2 things

1. Re-gap to 0.8mm or there abouts ($0)

2. Buy a set of splitfire coils ($650ish)

[Col-GTSX]

BTW sorry to sound rude or anything. I had thought of those things...

I just thought id put the problem in terms everyone can understand...

But my question still is current... (from first post)

Who told you to use 6/7's as your plug temp.... Im keen to run a test using 6/7's but i might just use $4 plugs that i got laying round. Im sure the iridium results would be much the same...

[blind_elk]

The standard coils were never designed with iridium plugs in mind.

To the best of my knowledge, the engines were designed to run with Platinum plugs. And IIRC, the tip on a Platinum plug is not all that different (size-wise) to the tip on an Iridium plug.

[Bobjones]

To the best of my knowledge, the engines were designed to run with Platinum plugs. And IIRC, the tip on a Platinum plug is not all that different (size-wise) to the tip on an Iridium plug.

Correct, that was due to the Platinums lasting longer and due to the crap intake not requiring its removal regularly.

Plug gap should ALWAYS be measure with the right equipment. It should also be noted that the Iridium plugs and the platinum ones only have a FINE layer of this coating. The terminals are NOT 100% Plat or Irid. SO be CAREFUL when re-gapping these plugs. I am sure that you can get 0.8 iridiums as far as I am aware.

Also note that the gap AND the temperature will have a bearing on the efficiency of spark dpending on a number of factors, including system performance, boost, fuel ratio, revs, intake temp etc.

The best bet is anything over stock boost gap to 0.8 and use a slightly higher heat rating, so 5's instead of 6/7 and it should be sweet. It is amazing home different ANY car will run with different or better suited plugs...

[Kaz200]

Every decent tuner I've ever been to has told me to use copper plugs in both the CA and the rb20. I don't know why you would gap the plugs differently, surely that would be worse not better. And with iridiums/plats at $20 each you'd want to be pretty careful not to break them whilst gapping.. they are hella thin. I don't see alot of point in iridiums unless someone can explain why they are worth the extra $$.

[Bobjones]

I might be missing your point but I am saying

1. Stock boost run about 1.1

2. Above stock use 0.8 gap

As for iridium supposedly they provide a higher energy charge, and last longer than coppers. I have only ever run coppers in rotors due to the higher fuel ratios and ease of removal.

And almost forgot, I don't pay any where near $20 each for Iridiums so I use them...

[lwells]

I don't see alot of point in iridiums unless someone can explain why they are worth the extra $$.

I have not seen anything that indicates they provide a better spark, like-for-like, compared to a copper plug (but nor have I looked for such info really). Everyone I have spoken too says to get coppers for hi-po cars and just change them regularly.

The benefit of iridiums is obviously the longer service intervals which, if you have a car where the plugs a PITA to get too -- and on some cars (Magnas I have heard, for instance) its a real bitch -- they make sense.

I think there is also a certain amount of wank factor. Saying you have iridium or platnum or plugs sounds so much cooler than copper.

LW.

[ed]

Are you guys who are using the NGK Iridium plugs using the Iriway's or the IX series?

That is what I use without gapping and no problems. (Iriway 7's)

http://www.ngk-sparkplugs.jp/sparkplugs/li...iris_lineup.asp

[Bobjones]

I am using the IX series,

these to be precise

BKR5EIX-11

these are gapped to 1.1 and heat rating 5

[Beer Baron]

you should not be using a heat range 5 plug in any turbo skyline... simple. seriously consider changing them to a colder plug like a 6 or even a 7 if you are making decent power. a heat range 5 plug could cause you some grief.

[Robo's]

Im using BKR7EIX-11