Ok so I know a lot of you guys with STR's are running the NGK IFR5N10 spark plugs. I emailed NGK just to verify if this plug was a good choice for the supercharged engine. This plug is designed for the normally aspirated 4.2 V8 engine only, not the supercharged version! So I then asked if I ran this plug in a 1 degree colder version if it would be more suitable for the supercharged engine. And again, he said: "the plugs that we offer are only for use in the naturally aspirated engine. Unfortunately I cannot verify that lowering the heat range by only one will be appropriate for this application"

So now what???

 

What does JTIS specify?

 

Jaguar designed and built the engine, not NGK. Use the part number specified by Jag.

 

I know what I would use!

 

Based on Norri's posted specs, I believe that I would go with the NGK-IFR-5N10

 

Hmmm, wonder why the guy there would tell me differently? Anyone running these plugs ever pull one after a few thousand miles to se how it's burning?

 

I'm wondering why you called NGK to ask. How would they know anything about somebody else's (Jaguar's) product?

The plugs were standard OEM equipment throughout type R production. Nobody has reported any problem with them.

 

Considering ngk was an oem supplier and spec out the plug for the application they might know at least what plug to use.
I just run the ngk bkr5es-11 copper, better plug for performance just doesn't last as long.

 

It's the other way around. Jag sets the spec, NGK produces a plug that meets it.

 

Pulled mine at 100K miles and put some more in. My car's just over 10 years old so if these plugs don't work I'm kinda puzzled!!

New ones have been in for 6K miles and I can't tell the difference.

Maybe the guy just didn't know Jaguar use them. He'd no particular reason to know, though it would help a little in case people ask.

 

That's what was intended, jag gives the requirements and ngk specs it out, sorry if the wording was funny

 

Well they manufacture spark plugs! So I called them simply because I did not see the S Type R as an option for plugs. Only S type. Kinda curious as to why the STR wasn't on there.

 

That is amazing! The guy at NGK you emailed describes himself as a "Technical and Training Specialist". Yet, the NGK website says:

Laser Iridium® spark plugs provide superior ignitability and long service life. Smallest tip diameter available Iridium / Platinum surfaces ensure slow wear rate providing stable idle, superior anti fouling, improved fuel efficiency and lower emissions

Best OEM Iridium spark plug available
Original Equipment Manufacturer approved design

You would do him a big favor by forwarding a copy of the JTIS specs that Norri provided.

 

Done! Haha

 

Well I decided to go 1 stage colder NGK laser iridium plug. #IFR6D10.... I will keep ya posted as to how they work

 

Spark plugs are produced in various heat ranges to allow the engine manufacturers to pick one that operates hot enough to avoid fouling but not too hot that it induces pre-ignition or excessive electrode erosion.

There's no other magic to it. Unless your car is experiencing one of the problems above, there's nothing to gain by changing heat range.

 

Per the info from this forum and others, there is no need to go to cooler plugs unless you are running crazy boost! Stick to the Denso's or the NGK's. I went with the 50k mile NGK's because this is what they use on the new 5.0 SC engines but that is probably not a good reason

 

I have a Nissan Sentra Spec-V and in the owners manual it gives 2 options for plugs. Regular temp and 1 stage colder. The 1 stage colder it says is for mostly long trips and highway driving. I also had a 2G turbo Eclipse with lots of mods that I ran 2 stage cooler plugs in. I feel a little safer running the 1 stage cooler plug. With that being said, my STR has a few mods as well and the only time I drive it is for long road trips! So again "FOR ME" I feel more comfy running the 1 stage cooler plug!

 

Also, I think it's pretty peculiar that Mercedes Benz "supercharged" engines as well as Chrysler Crossfire "supercharged" engines run the IFR6D10 plugs factory in their cars. Yet Jaguar has the same plug IFR5N10 for their normally aspirated engine as well as supercharged engine.....
Again it's all personal preference and this is what I choose to run based on experience in my car!

 

It's not going to do any harm is it? The worst that's likely to happen would be the plugs fouling.
Let us know how it goes.