Best spark plug for the 355?

NGK PMA7A are Iridium-containing electrode plugs (rather than platinum). IMHO these are the best plugs to run in a stock or slightly-modified F355. Highly modified - it would depend upon modifications (e.g., compression ratio, turbo, etc).

 

Franco, according to my local dealer, the currently recommended spark plug for the 355 is the same one used in the 360 the NGK laser platinum PMR8A, which is one heat range colder. The only other plug that correctly crosses over (to the PMR7A) is the Denso IU22. But I am not aware of anyone actually physically checking dimensions or trying them yet. I have used the NGK Iridiums that were supposed to crossover to the PMR7A, they are called the CR7EIX...but when they were removed from my car during the major, there was a slight difference in the nose projection found.

http://www.ferrarichat.com/forum/showpost.php?p=137390425&postcount=41

I think the safest best is to stick with the stock plugs, whether the PMR7A or PMR8A. I am currently using the recommended PMR8A with absolutely no issues.

Scott, I think you may be mistaken. There is no mention of Iridium in the Laser Platinum plug used in the 355. Here is the description:

LASER PLATINUM®

Laser Platinum® spark plugs provide high ignitability and longer service life. Dual platinum surfaces ensure slow wear rate providing stable idle, superior anti fouling, improved fuel efficiency and lower emissions.

Laser welded Platinum center electrode tip
Platinum disc welded to backside of ground electrode provides long life
Trivalent Metal Plating provides superior anti-corrosion and anti-seizing properties
Faster starts and quicker acceleration
Better fuel economy and lower emissions
Best Platinum spark plug available
Original Equipment Manufacturer approved design

 

Hugh:

What was the reason given for going to a "colder" plug? Also, NGK PMR7A are supposedly Iridium-containing electrode plugs, why are they called "laser platinum"? Iridium is a higher melting temperature metal than platinum, hence its purported to be able to survive the combustion process with temperature effects and less wear, while still retaining the conductive ability of platinum. Most plug manufacturers use Iridium in their "top of the line plugs". Am I off base in my thinking/beliefs?

P.S. Hugh just read your updated post. Well, I'll be damned!! Thank you very much for correcting me! The Ricambi website lists the NGK PMBR7A as an "Iridium", not "Platinum" plug. I stand corrected. My sincere apologies for stating incorrect information. This will teach me to base my beliefs on only one source of information. Mea Culpa!!!!!!!!

 

Scott,
No idea on why the colder plug...it could be as simple as a parts stocking issue. (fewer part numbers to inventory). I was initially concerned of plug fouling or other issues, but the car drives just fine. I know a couple other guys who had their cars dealer serviced here on Fchat also got the PMR8A and having no troubles.

Dave

 

PMR8A is only for 05.1994 - 01.1996 = 2.7
PMR7A is only for later cars 1996 - = 5.2

If you run a 2.7 with the wrong sparks you'll foul them after some cold starts on a shop yard.
(have a look for the '8' if you want to have the engine running on eight pots)

cinque

 

Interesting! Thanks for the post. I wasn't aware that they differentiated plugs for the 2.7 and 5.2 cars, but it makes sense with the different ECUs. That's what I love about FChat - the fantastic knowledge-base out there! You learn something new every time you log on.

 

Where does the CR8EVX fit in to the equation?

Listed on the NGK site as for
Model F355 Berlinetta
Years 07.1994 - ...

By their description (VX) it is a platinum plug -

http://www.ngk.de/VX_spark_plugs_Platinum_plugs.693.0.html

 

Could be an error John. Check my post above about the CR7EIX, which is the Iridium equivalent of the VX platinum plug, though in a 7 heat range, rather than an 8. VX plugs are being discontinued in favor of the Iridium. But as shown in my post, the nose projection is a bit shorter than the oem plugs. I used them for about 8k miles, no problems, but the dealer says it probably was not optimum.

 

[[[[flame suit on]]]]

Detonation prevention. First step when cranking up the boost on a forced induction car is to run a colder plug. I'm currently running two ranges colder then stock in my 928. It's also being force fed 17psi of boost the factory never intended

There is always the fear of fouling during normal driving and rough idle if the plug is too cold. Old school rule of thumb is to run the coldest plug you can without fouling. Since driving habits vary, it’s hard to say what plug will work for everyone. IMO this is why most factory installed plugs are too hot. The factory has to create a base setup for the motor to handle everything. Even driving in a parade and constant stop / go traffic.

This is where the flame suit will come in handy.
Silver, platinum, and even iridium plugs are not the best for ultimate performance. My tuner, who is known for his 2.2 liter turbo street engines that belt out over 700hp at the wheels, will never run anything but copper plugs, ever, no exceptions.

Auto manufactures are under extreme pressure to make sure their vehicles are as clean as possible out the tailpipe, performance be damned, for as long as possible.
Silver, platinum, and iridium plugs do last longer, as well as multi-electrode plugs. This is how manufactures were able to start bragging about 100,000 miles between “tune-ups”. The plugs last that long so the tail-pipe is cleaner.
This is also where the hotter plugs come in. Since the oil vapor is going straight into the intake, the hotter plug helps insure any oil entering the chamber is burnt off (I'm actually 50/50 on this theory, too much conflicting data out there).
This is also why I completely re-designed the oil vapor system on my 928, no oil vapor going into my engine

How does this all apply to the 355 motor? Not sure since I do not really dabble in N/A engines. But IMO the same principles should apply, especially with a very high revving, high compression motor like the Ferrari.

Maybe the high revving nature of the 355 motor means a hot plug is needed to prevent fouling at low RPM’s and the “exotic” metals to help protect the plug longer?
Not sure I would buy that reasoning, but anything is possible.

 

According to the NGK catalogue in bookform and their website you should use PMR8A in the 2.7 engine.
That's why I use 'em.

PS: better trust NGK not your mechanic in this topic

cinque

 

The nose protrusion of the PMR7A and PMR8A are the same. How did you confirm the correct plugs for the 2.7 versus the 5.2?

I guess the reason I am asking, is I was informed by Ferrari of Seattle, that Ferrari changed (at least for the 5.2) from recommending the PMR7A to the PMR8A. NGK may not be aware of this change.

 

Okay, then NGK is probably wrong.

Here is what Daniel from Ricambi has to say:

"I have always believed:

PMR7A for the 2.7
PMR8A for the 5.2

BUT.... PMR8A has been updated to PMR8B. The 8B are very hard to find and we keep buying as many as we can get, but they keep going stock-out from NGKUSA."

(I would think that Daniel and FNA dealers have the most up to date information from Ferrari SPA.)

 

Thanks for the post. I guess my question really should have been why did Ferrari, 12 years after the 1996 models were introduced, start recommending the use of a "colder" plug? Were mechanics noticing some type of problem, long-term reliability issues, factory research, etc....

 

My 2.7 is igniting NGK PMR8 A (B).

I tested PMR7A as well, but they tend to foul if you are not going longer stints. Also the starting behaviour is better with PMR8A.
Backround: The mixture by 2.7 motronic is rather rich in comparison to the leaner 5.2. (more 'domestic' because of stricter emission limits)

cinque

 

That's interesting since NGK's get colder as the number goes up (Bosch are the opposite).

P = Platinum
M = Thread 10mm, Reach 19mm, Hex 16mm
R = Resistor
8 = Heat Range (higher number = colder)
A or B = not sure yet, still looking. This is a "special design" mark not on my usual charts.

I'm trying to find the Bosch equivalent to this plug. Side question - is changing the plugs on the 355 a big deal?

 

From my checking, there are no equivalents, other than the previously mentioned Denos IU-22, which Denso claims is a cross to the PMR7A. I am unaware of anyone confirming that either visually or in use.

Changing the plugs is not hard, but a bit time consuming. You must remove a number of small Allen headed screws to get the cover plates off the cam covers; this gains you access to the plug wires and plugs. It is a good idea to replace the paper gaskets for these covers, as well as the foam block where the plug wires enter the came cover when opening this up. Since these seals keep water out of the plug wells, it is very important they seal well.

 

Cool, thanks for that info. I'm so use to tossing high dollar platinum plugs for Bosch or NGK Copper I had to ask

My fathers 355 has a strange miss at idle, very subtle but it's there. After going through a few issues like a stuck thermostat & dirty MAF there are no more codes to chase after. Back to basics, check the plugs!

 

I have the Denso on my 95. No issues.

 

Check the plug wires. If they are original, there are probably one or two bad ones, not an uncommon problem. www.kingsborne.com has good prices for replacements. They use the oem Beru parts on each end, and a good quality wire. Looks oem. You can order colored wire like red if you want.

 

Thanks for the link.

On my short list is a crimp tool and necessary ends to make my own plug wires for my other cars. Are the ends on the 355 prone to failure? If not I would prefer to buy bulk wire and make my own.
This all started a while ago when Bosch stopped using the Beru ends on their 928 wire sets. The "new" made in china ends did not fit very well so I detached the wires from the ends and rebuilt them using the old Beru parts from the old set.
I've been thinking about buying some bulk ignition wire anyway since I'm about to put a custom ignition system on my 928 so I need to make wires that are not stock length.

 

I believe the failure point in the factory 355 wires is the wire itself. Because they are all squeezed and packed tightly into the cam covers. Add all the engine heat... There are threads from Rifledriver and others pointing out the specific wire or two that most commonly fail.