Fellas- Been researching plugs for a 5.2 Motronic and have come to the following conclusions: -NGK PMR8B: Stock replacement, one heat range colder from the 8, most utilized on the forums -Denso IU22: Iridium stock replacement. Not much info on these other than its an iridium cross reference for the NGK -NGK ZMR7AP: laser platinum replacement, must be gapped Now before everyone jumps to conclusions on simply purchasing the PMR8B, would love to hear some healthy debate on moving to the Densos. I have owned quite a few cars over the years and always have preferred a copper electrode, performance wise, up until the new iridium technology has become prevalent. I have always had much more luck using copper for making more power, but iridium has been a nice compromise due to longevity. Does anyone have some first hand experience on using iridium on our cars, specifically the IU22's?
I've heard the Denso plugs are good in other applications, but have never run anything but NGK stockers in ferraris of the past 20 years. I will say I have noticed the NGKs on 355s seem to really take a beating and miss a bit at idle, and a new set corrects the issue. I can only say this was the case with my personal car, but I may give a set of Densos a shot if this happens again.
Never have had satisfactory experience with any ND plug I have used. I have never had any reason not to use NGK on the Ferrari's.
Brian, Which do you prefer on the 5.2 Motronic cars? The original PMR7A or the later PMR8B? I have used both without issue, but stuck with the PMR8B based on hearing folks claiming the PMR8B was being recommended by FNA. I figured if the colder plug worked without fouling (did for me), that was a good thing...
Is your reference to ND, Denso? I've used Denso on a couple of other platforms I've owned with great success! Worst case is the PMR8's - but I may give the Denso's a shot - with a simple gap adjustment. It actually should be IU24's as 22's are in the 7 heat range.
ND = Nippon Denso Their reputation was such they adjusted the name to reinvent themselves. They must work OK in something. Never been a fan though.
http://www.ngksparkplugs.com/techinfo/spark_plugs/partnumberkey.pdf Premium Platinum, ø 10, 19mm (3/4” Reach, 16mm (5/8” Hex, Resistor, 7 or 8 heat range, tip shape A or B. If you can find another manufacturer equivalent, I see no reason it wouldn't work. PMR7 is specced for 2.7, PMR8 for 5.2. The B is just the end shape, doesn't really matter. I have a set of both, switched from PMR8 to PMR7 over the winter and noticed zero difference (2.7 car). ymmv.
I have had quite the experience with Denso parts as my background is a Supra and have never had an issue. Their reputation has always been flawless in my books - not sure if a "reinvention" was the purpose
Good info. I emailed NGK several years ago to ask what the functional difference was between a PMR8A or PMR8B and they said "nothing" and that either should work fine in the F355 if that is what Ferrari was now spec'ing. (their online database still shows the original spec PMR7A) If they are functionally the same, why make both??
As I recall the B has a platinum button on the ground electrode instead of just on the center. There were some issues of misfire codes on high mile plugs they were correcting. It was designed for Ferrari. Where NGK called the A a premium platinum with the A denoting a special shape ground electrode the B is called a double platinum.
Thanks Brian for providing "the rest of the story". I kind of figured there is a reason for everything...
BTW, I wanted to comment about iridium and longevity. Both iridium and platinum have similar longevity. Note that NGK makes long life versions of both. NGK Laser Platinum PMR7A and PMR8B are actually long life plugs, made for OEM specs...supposedly designed for up to 100k change intervals. I came across this fact when getting plugs for my girlfriends Toyota Tundra. As I was shopping online for NGK plugs, I noticed the claimed higher performance NGK IEX iridium plug was less expensive than the standard NGK Laser Iridium IR iridium plug (what Toyota uses as OEM). When asked, NGK said either will work fine, but the "Laser" series IR plug is more expensive because it is the OEM plug, designed for 100k replacement intervals. Their IEX is recommended to be replaced at 50k to 60k intervals. The fine wire tip simply will not last as long. But NGK feels the IEX offers superior performance...
No issues with my stock plugs. Simply wanted to try something different for increased performance - based on my past experiences on other platforms.
The major ignition problems on the 355 are typically related to worn or defective spark plug wires. Making sure your wires are in good shape with no shorts to ground is key, beyond that, unless you are converting to coil on plug, I doubt a spark plug is going to make a measurable improvement. Best improvements I had during my ownership was simply making sure the car was running optimally. At the age they are at, things like getting the throttle bodies all adjusted properly and in synchronization...those really help the drivability. (my local dealer is really good at that, which is not well understood)
I just installed a set of iridium NGK plugs in my 92 348 ts.The only complaint I have is regaping the iridium plugs can be nerve racking.If you break the fine iridium wire during the gegap process you are SOL
