Thanks CCKen! its weird that the ZFR5N is half the price of the FR5-1.

 

Everyone's website when I plug my 98 4.0 in says FR5-1. What's the difference between the 2 and why is the ZFR5N cheaper?

 

The FR5-1 is probably more expensive than the ZFR5N plug because the FR5-1 has limited use/limited production, whereas the ZFR5N is used in many applications and is produced in larger quantities.

 

I'd like to see the ZFR5N next to an FR5-1.

 

Took this pic back during the FR5-1 debate in 2013..

 

Z is extended tip and N is special ground electrode.

Could these be the holy grail of plugs for us?

 

What's the bottom one in the photo that I just stole from you?

 

I couldn't find any data on the ZFR5N electrodes, if they are both copper like the Champion ECC plugs. Seems funny that when Champion came out with the RC12ECC (Double Copper) plug that NGK came out with the ZFR5N.

This is what the RC12ECC looks like compared to the RC12LYC plug.


Note that the EEC has both center and ground electrodes made from Copper and the LYC only has the center electrode made from Copper. The LYC ground electrode is Nickel plated steel.


I was looking for something like this for the ZFR5N plug.

 

Now I'm tempted to put the ZF5RNs in my Renix.

 

RC12ECC

 

Here's some data I found tucked away in my files. I don't know where it came from a magazine or something. A Word document so I will copy and paste here.




A Distributorless Ignition System uses a Waste Spark arrangement, where a single coil fires the spark plugs on the “waste” (exhaust) stroke as well as the “power” (combustion) stroke. The Jeep 4.0 uses three coils, each firing two plugs. This system was introduced on the 1999 Jeep Grand Cherokee and the 1999 Jeep Wrangler.

This system helps to accomplish firing the plug as the exhaust gases leave the cylinder to help reduce exhaust emissions. Any unburned fuel can be burned prior to reaching the catalytic converter.

Due to the design of the system, Waste Spark Ignition systems place an unusual demand on the spark plug. Because the plug fires in both directions (positive and negative polarity) this increases the wear rate of the spark plug because the plug erosion is occurring at the center electrode and the ground electrode (as opposed to traditional ignition systems that mostly wear the center electrode).

Champion recommends Iridium or Double Platinum plugs in a waste spark system to decrease gap erosion. Chrysler elected to use Champion RC12ECC “Double Copper” spark plugs instead of Platinum plugs at build (Cost). The Champion RC12ECC plugs have a Copper center electrode and a Copper ground electrode which is intended to address the reverse polarity erosion issue it is assumed.

Even though the 1999 model year Jeep Cherokee, XJ body, 4.0 Liter engine, didn’t have the Waste Spark (Coil Rail) ignition system, Chrysler introduced the use of Champion RC12ECC spark plugs for all 1999 model year 4.0 engines due to the introduction of the Waste Spark ignition system on the Grand Cherokee and the Wrangler in 1999, and was continued through model years 2000 and 2001 Cherokee XJ, including the Jeep Grand Cherokee and Wrangler 4.0 up to end of production.

 

The N suffix means special ground electrode......

 

Well, here's what I did.

I removed the 36,000 mile FR5s from my MJ which has 190,000 miles on it.
The gaps were all right at .042".
I regapped them to .035" and reinstalled them.
Took a good drive today and here's what I noticed:
Started up cold a bit more quickly. Idle was a bit better and throttle response was also.

Went to NAPA and bought 6 new NGK ZFR5N plugs. Came home and let the truck cool down.

Checked the gap on the new plugs and they were all exactly at .035".

Installed them and did a quick comparison.

Steadier and smoother idle upon start up.

Smoother idle when warm.

Throttle response even a bit better than the regapped FR5s.

My old plugs on each side of a new ZFR5N.

 

quick question. I installed accel wires, cap rotor & plugs, It drove fine for a while, but I noticed a slight miss and a slightly rougher idle and my fuel milage dropping to about 11 mpg. I've never been that impressed w accel plugs, so I'm about to swap them out and try a set of Champion Platinum Power plugs (RC12PEC5) as they were in stock and on sale. Anyone have any experience with these?

 

Just use NGK ZFR5Ns