Best spark plugs for the XJ ?

[FUNKYTEE5]

Ok, let me add this in then, i'm getting MSD 8.5 performance wires,(maybe taylors), Blaster 2 or 3 coil pack and down the road will be MSD's offroad ignition box.....

SO, i really want to match up the plugs to the ignition set up and ofcourse whats good for the 4.0 HO. motor.

Im down to 3 choices, bosch triple platnums, splitfire triple platnums,,,OR NGK PLATNUM IRIDIUM HI TEMP PLUGS!!
The NGK plat iridiums will produce the best overall spark & efficiency but only if my entire ignition system is upgraded as i stated above.

Now does anyone agree with that set up for increased overall ignition performance tuneup & efficiency, "OR" does anyone disagree with the iridiums in the 4.0 HO.????

The only thing that you will probably lose with cheaper plugs is overall wear resistance. The spark will still most likely be determined by the ignition system. Platinum and Iridium are compounds that do not degrade like a standard steel electrode. That's why some manufacturers have overhyped tune-up intervals with them, 100k!. Iridium plugs are best suited in boost conditions where the resistance across the plug gap gets very high due to the amount of air/fuel being compressed. At that point, misfires can occur with standard type spark plugs and it greatly affects power output. Iridiums have low resistance and one focused point where the spark can jump across, making it easier for the spark to cross the gap, leading to less misfires under high boost conditions. With a N/A motor with stock computer, cam, and compression misfires aren't really an issue. The stock 4.0 ignition is actually very good, and with a plug wire upgrade and maybe a coil, it performs excellent. Ask Dr Dyno. And if you have the late model coil pack ignition it's even better! There's alot of power to be tapped into the 4.0 and not a whole lot of it is in the ignition system. If your set on doing ignition upgrades, go for it! But if you want to see some real power gains focus on: cold air, heat shields, cam, exhaust, headwork, higher compression, ECU upgrades etc... Good Luck.

FUNKYTEE5

 

[BIG-G]

OK, im gonna get NGK's but im trying to find a platnum series! All ive came up with is V groove $2 buck plugs. I know they have platnums but i cant find em.

Can anyone send a link or send me into the right direction please.

 

[XJ4.6NOS]

What's the part# for the NGK plug that fits the XJ?. Did any body try Split Fire Spark Plugs? I am using champion but will buy Split Fire next time.

Anybody care to put the part# for the NGK spark plug that fits the XJ.!!!

 

[BIG-G]

Anybody care to put the part# for the NGK spark plug that fits the XJ.!!!

Yes i second that question cauce 3 parts stores and no one had NGK's for my XJ !

 

[sjx40250]

I am convinced that Champ truck plugs are the best. I ran splits for a couple of years and the truck failed emissions tests. changed to Champs and it passed. Emailed Splitfire up and got a phone call. After a 20 min discussion, they admitted that they cause the vehicle to run lean in order to get the improved MPG. They also admited to designing the plug to cause the ECU to run near the top of the trim range.

My 92 came with Bosch Plats and upon removal, there were nearly no insulator left on any of the 6! Hey, don't screw with a good thing.

 

[ILLXJ]

Yes i second that question cauce 3 parts stores and no one had NGK's for my XJ !

I will post it Mon. night. I just went to Napa & they looked it up for me. JIM.

 

[bajacalal]

In my old and jaded opinion.....multiple electrode plugs are nothing more than marketing bling-bling....I run a 75HP nitrous shot on my 15 to 1 compression 1327 CC Kawi dragbike using standard B9ES NGK's....11K rpm....no problems.

I agree, with you to a point. They say the extra electrodes allow the igniting mix to spread more evenly in all directions. But look at any 4.0 head. The spark plug resides way, way over to the side so, bearing in mind that that I'm not an engineer, there would be hardly any effect. The plug is too close to the cylinder wall for the extra spark to do good over there. In applications where you have a wide bore (oversquare) cylinder, high compression with a centered plug (think jap dohc engines) I can see the point.

 

[corbinafly]

FWIW here's the setup I'm running on my stroker.

MSD offroad 6 ignition
Performance Distributor screamin' demon coil
MSD super conductor wires
Denso Iridium plugs gapped at .050".

Before I got my stroker, my 4.0 was barely running. It was fine then one day on the way home from a job site, it suddenly felt like it was running on 3 cylinders. I haven't torn the motor apart yet to see what had gone wrong. But anyways while trying to diagnose the problem I bypassed the MSD ignition to see if that was the problem, and it wouldn't start no matter what I did. Then when I plugged it back in it started up just fine. Of course it still felt like it was running on half it cylinders. Same thing happened at the diagnostic shop while trying to find the problem.

The point is that the MSD kept my motor running while the lack of wouldn't. I'm not saying that it would necessarily benefit a motor that didn't have any mechanical problems. Just some info to digest.......

K

 

[Sarge]

I agree, with you to a point. They say the extra electrodes allow the igniting mix to spread more evenly in all directions.

Except for the fact that electricity follows the path of least resistance...not the paths of least resistance. In other words that multi tipped plug functions as a single tipped plug. The others are there as a marketing deal.

Sarge

 

[ErikL]

a few years ago with my camaro (502 BBC 10-71 blower 12lbs of boost) i talked to the manager at napa, asked him about the benifits of platinum, iridium, multiple electrode, and grooved plugs...... he said platinum doesnt really offer any benifits other then long life..... they used them in cars where you couldnt get to the plugs without pulling the motor ( newer camaros trans ams....stuff liek that) iridium was good for high compression, high boost cars (more import then my case) and for me ac delco was the best possible plug..... degreeing the plugs will help out alot more then anything else..... making sure the gap is in the correct position in the combustion chamber.... to do this you really need to know the design of your head and valve placement, then mark the plug and keep trying plugs until it lines up correctly. splitfires and plugs like that do nothing....at all...... ngk v groove is good, but not some godsend to ignitions same with accel u groove plugs..... in all of our race cars (hp varies from 500-3000) theres no special magical plug, nosuper top secrect nasa designed electrode element.... we run ac delco, and NGK..... thats all in both distributor and magneto driven ignitions

 

[JeepSpeed]

So, as always, most people agree that good old fashioned truck plugs are the best for the ole 4.0L. But, on a stock or close to stock engine, what's the best gap to run those plugs at for power production/efficiency?

 

[boise49ers]

a few years ago with my camaro (502 BBC 10-71 blower 12lbs of boost) i talked to the manager at napa, asked him about the benifits of platinum, iridium, multiple electrode, and grooved plugs...... he said platinum doesnt really offer any benifits other then long life..... they used them in cars where you couldnt get to the plugs without pulling the motor ( newer camaros trans ams....stuff liek that) iridium was good for high compression, high boost cars (more import then my case) and for me ac delco was the best possible plug..... degreeing the plugs will help out alot more then anything else..... making sure the gap is in the correct position in the combustion chamber.... to do this you really need to know the design of your head and valve placement, then mark the plug and keep trying plugs until it lines up correctly. splitfires and plugs like that do nothing....at all...... ngk v groove is good, but not some godsend to ignitions same with accel u groove plugs..... in all of our race cars (hp varies from 500-3000) theres no special magical plug, nosuper top secrect nasa designed electrode element.... we run ac delco, and NGK..... thats all in both distributor and magneto driven ignitions

Now if this is true there sure are a lot of guys out there wasting good money. Glad I'm not one. Though next set I'm going NGKs as opposed to Champs. If I get a part number. Now with that said, I'm not sure a guy from napa would be any more realible then a lot of the guys who have tried all different set ups and swear by the results they have seen. Mileage would be a hard one to argue. If your mileage boosts how else can you explain except it ignites better. This thread kind of has that (what kind of tire should I buy ?) ring to it. This could go on forever.
NGK number would be nice. For a Non-HO.

 

[ILLXJ]

Here's what I run. NKG V-Power Part # FR5-1. I run these in both my 96 & 92. HTH. JIM.

 

[boise49ers]

Here's what I run. NKG V-Power Part # FR5-1. I run these in both my 96 & 92. HTH. JIM.

Thanks, but I wonder if the Non-HO would be different ? I would think it would be with the amount of fuel coming in being more. I may be wrong though.

 

[FUNKYTEE5]

Thanks, but I wonder if the Non-HO would be different ? I would think it would be with the amount of fuel coming in being more. I may be wrong though.

Yes there's more fuel delivered in a HO due to larger injectors. But the power output increased with the injector size accordingly. The A/F ratio is still dictated by the factory ECU and governed towards emissions. Being too rich would only be a result of the ECU/fuel system not functioning properly and/or modifications to the system.

 

[corbinafly]

I'm not sure a guy from napa would be any more realible then a lot of the guys who have tried all different set ups and swear by the results they have seen. Mileage would be a hard one to argue. If your mileage boosts how else can you explain except it ignites better. This thread kind of has that (what kind of tire should I buy ?) ring to it. This could go on forever.
NGK number would be nice. For a Non-HO.

I think that increases in mileage would be a hard one to argue IF the plugs that were replaced were in good condition and all other things remained unchanged.
I think a lot of people switch to a new plug after running say 15,000 or more miles on a set. Of course, after all those miles, the existing plugs weren't at their optimum performance level. Than the new "improved" plugs go in and a benefit is gained. Might have gotten the same benefit with the same plugs only new. Hmmmmmmmm.

K

 

[MudDawg]

I can see increases in fuel economy only if the original problem was the plugs or some other problem that was corrected during the ignition system refurbishment.

 

[ErikL]

Now if this is true there sure are a lot of guys out there wasting good money. Glad I'm not one. Though next set I'm going NGKs as opposed to Champs. If I get a part number. Now with that said, I'm not sure a guy from napa would be any more realible then a lot of the guys who have tried all different set ups and swear by the results they have seen. Mileage would be a hard one to argue. If your mileage boosts how else can you explain except it ignites better. This thread kind of has that (what kind of tire should I buy ?) ring to it. This could go on forever.
NGK number would be nice. For a Non-HO.

people will buy anything thats advertised well..... why do you think there are still so many conventional plugs out there, and all the major manufactuers are still useing regular style plugs? i could sell 1 billion dollars worth of dog shit, but at the end of the day i still sold dog shit..... knwo what i mean? if theres people willing to buy it and try it, then they will keep making them.

 

[boise49ers]

I think I'm getting the picture. Still sticking with the NGK next time. They aren't much more. Dog shit for sell eh ? I could make a fortune. :laugh3:

 

[ErikL]

NGK is a great plug, they have always worked well for me in the past in both street and racecars...... dont do the iridium, or platinum.... if you do i have beachfront property for sale if youre interested..... its in nebraska, good place to retire to