• Protip: Profile posts are public! Use Conversations to message other members privately. Everyone can see the content of a profile post.

Question about NGK spark plugs

Rating - 0%
0   0   0
Joined
Jul 21, 2022
Messages
25
Is there any issue with using these plugs in a natural aspired NSX, no modifications? They seemed to be an upgrade from stock and were cheaper than stock so I bought these. Should I send them back or use them?

NGK 6741 Laser Iridium; Pre-Set Gap: 0.044" Info
OE-Recommended Gap: 0.044"

Center Electrode Core MaterialCopper
Center Electrode Tip MaterialIridium
Electrical Terminal TypeNon-Removable Nut
Gap Size (IN).044
Ground ConfigurationStandard
Ground Electrode Core MaterialNickel
Ground Electrode Quantity1
Ground Electrode Tip DesignStandard
Hex Size (IN)5/8
Insulator Height (mm)50.50
Manufacturer Heat Range6
Part NumberIFR6E11
Reach (IN).75
Resistance (ohms)5000
Seat TypeFlat
Stock Number6741
Thread Diameter (MM)14.00
 
Rating - 0%
0   0   0
Joined
Nov 3, 2011
Messages
2,817
Location
Saskatchewan, Canada
You have a 1991?

6741 is the stock code number which should be part number IFR6E11 which is the correct heat range and dimensions.
 
Rating - 0%
0   0   0
Joined
Jul 27, 2007
Messages
6,030
Location
Denver, CO
The best plug for the NSX is the double platinum plug. NGK, Denso and I believe Champion make them. Iridium is only really needed for turbo engines.
 
Rating - 0%
0   0   0
Joined
Jul 21, 2022
Messages
25
Honcho should I get rid of the laser iridium now or change them them out for the double platinum next time I change my plugs?
Any harm running the laser iridium that I have now, haven't put them in yet. I do not have force injection.
 
Rating - 0%
0   0   0
Joined
Nov 3, 2011
Messages
2,817
Location
Saskatchewan, Canada
Iridium plugs and double platinum plugs are pretty much identical in how they will perform in the engine when new. They are both fine wire plugs that look physically identical (as opposed to a more conventional copper / nickel fat electrode). Iridium plugs post-date platinum / double platinum plugs. In fact, Denso didn't introduce iridium plugs until 1997 -98 so they definitely post date the NSX as a technology. NGK iridium plugs are the OEM spec spark plugs on my Son's 2005 Acura RSX so its not a forced versus naturally aspirated related decision. I run NGK iridium plugs in a 1971 Volvo B20E engine just because neither NGK or Denso sell a platinum in the correct heat range and fit.

Iridium has a higher melting temperature and is harder than platinum. On that basis, the iridium plugs will have a longer useful than platinum plugs. Denso describes a useful life of 200,000 km for its double iridium plugs. After they had been in my car for 10 years (not a huge number of miles), I replaced the platinum plugs in my 2000 with new platinum plugs. The old plugs looked pretty much like new, so I think for most owners of stock NSXs there is probably no up-side to spending more money for iridium plugs if you respect the factory recommended service intervals. Conversely, I don't see any down side to using iridium plugs. If you picked up the iridium plugs for a lower cost than the double platinum plugs I would stick with them.

How good was the price on the iridium plugs and who did you get them from? There was / is an issue with counterfeit NGK and Denso iridium and double platinum plugs on the market. The counterfeits were conventional plugs that had their electrodes machined to look like fine wire plugs and then new part numbers stenciled on them. You can do a Google search for a guide on how to spot counterfeits. If you purchased your plugs from a reputable vendor such as RockAuto or similar, then you are probably OK. If you purchased it from Supernicexyz on EBay I would be suspicious.
 
Rating - 0%
0   0   0
Joined
Jul 21, 2022
Messages
25

NGK Laser Iridium 6741. $9.21
NGK double platinium 555. $8.70

I thought if I could get a better plug for .50 cent more it was a no brainer?
 
Rating - 0%
0   0   0
Joined
Jun 8, 2011
Messages
359
Location
Bucks, UK
Unless the engine is requesting the higher spark energy or something exceeding the original design spec due to modifications, etc, you will gain almost nothing by using the iridium over double platinum spark plug on the NSX engine with the standard INJ spec, OEM IG coil/dowel time, fuel pressure, etc.

For the clarification, iridium plug will very likely to have some benefits over the classic standard one.

With our NSX engine, most likely, you will be replacing the plug before the recommended maintenance interval not because of the plug itself but due to moisture getting inside the plug hole especially at the rear bank.

In Japan, NGK doesn't even list the iridium, the latest ruthenium or even the classic standard spark plugs when specifically searching for the plug for Honda NSX and only lists the PFR*G-11.

This is because they always recommend using the specified OEM plug by the car manufacture or the one recommended by NGK for the specific make/model.

You will only see the alternative options such as the iridium, ruthenium ones when searched for the compatible models for the PFR*G-11.

They need to protect themselves from the unknown factors when recommending the alternative ones so always check the small prints.

Please note that with JDM NSX, it never received the 3pin IG coil and stayed with the 2pin style and thus, no changes in spark plug spec (PFR*G-11).
Outside of Japan, depending on the country spec and the year model, you may have PFR*G-11, PFR*N-11 or PFR*L-11 from the factory.

Years ago, I contacted NGK Japan asking about the spec difference between these 3 but due to IP reason, they were only allowed to say that they were based on the design requirements provided by Honda so must be something to do with the changes in misfire detection or something.

On NGK website outside of Japan, when you search the plug for Honda/Acura NSX, it will include the compatible alternative option addition to the OE spec PFR*G/N/L-11 and you'll even see the ancient ordinary standard plug included.
Again, you'll always see the small prints if using these alternative ones.

So, you can use these alternative options over the OE spec but doesn't have to.

Just be careful with the recommended service interval when using non-double platinum one.
Some, including the specific iridium one has much shorter life cycle.

Also, with 2pin style IG coil, make sure to check the shape of the top terminal of the non-OEM plug.
Never use the one with a hole (popular with removal/screw type top terminal) or deep dimple.
It can chew into the spring loaded 2pin IG coil internal terminal and eventually cause failure.

There are many fake NGK plugs on the market.
NGK has many factories around the world and using different packaging so it doesn't help….

Kaz
 
Rating - 0%
0   0   0
Joined
Jul 27, 2007
Messages
6,030
Location
Denver, CO
Kaz beat me to the punch. The iridium will not hurt your NSX, but it is not the specified type and likely will not last as long as the double platinum plugs. Of course, very few people drive their NSX to the full spark plug change interval, so it probably won't matter.
 
Top