After doing some research with the search function, I have concluded that the NGK 5464 is my best bet to replace my stock spark plugs. Common knowledge dictates that boosted engines like cold spark plugs, however I cannot find any other brands that have cooler than stock ratings. Any ideas before I pull the trigger on the NGK's? Thanks

 

Why would you want to go colder than the stock plugs, even if they are available?

 

You have a factory built super charged car. I think Jaguar would spec the correct heat range plugs.

I don't see what gains you will get?? Are you have some problems now?
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I read that denso iridiums are colder than the NgK iridiums, also Eurotoys recommend using the denso iridiums after pulley upgrade. Currently I'm running the NGK iridiums the 5464s without any problems with my pulley upgrade from Mina.

 

Stick with NGK plugs.... anything else causes issues down the line...anyway, you said it yourself - the NGK's you currently are using are running with no problems...

 

A colder plug *might* be beneficial depending on the way the car is run.

But, that determination needs to be made by "reading" the plugs.

So, it is part of the "common knowledge", but the knowledge is to be applied where required to address a known, identifiable problem.

Every deviation from specification is a compromise with costs and benefits. Indeed, the specification itself is a compromise.

 

Interesting, do you have a link or do you just remember that? Thanks for the info.

 

Without getting into a huge debate, I know boosted engines like cold spark plus. I used to own a supecharged buick (L67) and everyone used one or two step colder autolite plugs. That could be comparing apples to oranges, but if it helps the car why not?

 

There's no technical reason to believe that running a colder plug than optimum will do anything other than possibly cause the plug itself to foul. Plug heat ranges are in no way connected to 'making power' but exist simply to be hot enough not to foul but not hot enough to melt themselves into oblivion or become a source of pre-ignition. The heat range of the stock plug apparently achieves that.

 

Its on Eurotoys website if I remember correctly reading about the benefits of using Denso Iridiums etc...but I always stuck with my NGK indiums regardless. *Going the Denso route is very intriguing and If I ever had to do my plugs again I would use Denso Iridiums instead to try out.

Found this question and answer from the FAQs from Denso's website thought I would share it with you guys....

Why are there different heat ranges? Which one should I use?

A. Part of your spark plug’s responsibilities, in addition to firing a spark, is to remove heat from the combustion chamber. This is accomplished by channeling the heat through the insulator material and metal housing. From there, the heat is transferred to the cylinder head where the engine cooling system can go to work. A spark plug’s heat range is its ability to dissipate heat. The “colder” the plug, the more heat it can channel out of the combustion chamber. In a performance application, colder heat ranges may be necessary to handle the extreme temperatures brought on by higher compression ratios, forced induction, and high RPM’s. While “Colder” plugs may seem to be the way to go, please remember that the spark plug must achieve its “self-cleaning” temperature where it can burn off fuel and carbon deposits. Otherwise, the plug could “foul out” where it is prone to misfiring and poor acceleration. A plug that is too “hot” can overheat, also causing power loss, detonation, pre-ignition, and possible engine damage. A good, general rule of thumb is to start with the factory recommended heat range. For every 75 to 100 hp you add to your engine, you may go to the next colder step. DENSO heat ranges move up as they get colder; 16 would be our hottest Iridium Power plug, 34 would be our coldest (ranges; 16,20,22,24,27,31,34)

 

Excellent info, this bit is what counts. The HP increase precipitates the need for a colder plug, not the other way around.

 

Some of us have upgraded our STR pulleys to 1.7lbs-3lbs, did the whole exhaust mod and put on high performance Air Intakes...etc... Now won't we modded select be inclined to benefit from using colder grade spark plugs as mentioned in that small FAQ's section from Denso than the standard OEM plugs? IF so then its completely understandable that Eurotoys suggest going with the Denso Iridiums as the preferred choice.

The “colder” the plug, the more heat it can channel out of the combustion chamber. In a performance application, colder heat ranges may be necessary to handle the extreme temperatures brought on by higher compression ratios, forced induction, and high RPM’s. While “Colder” plugs may seem to be the way to go, please remember that the spark plug must achieve its “self-cleaning” temperature where it can burn off fuel and carbon deposits.

 

The OP makes no mention of having added the quoted 70-100HP required to be able to successfully run never mind 'need' a one step colder plug- nor does Denso intimate in any manner that a colder plug is of other benefit.

'Channeling heat out of a combustion chamber' other than to avoid pre-ignition or mechanical failure is not of benefit to performance.

 

One need not add some magical number of horsepower to "successfully run" a colder heat range. Nor, is it necessarily a bad thing.

Some people prefer a colder heat range, and see benefits in boundary conditions. Even on a completely stock engine.

The trick is to know and understand the tradeoffs.

 

Here's an interesting paper to read, with some excellent illustrations on the differences between hot vs. cold plugs

http://www.ngksparkplugs.com/docs/te...plications.pdf

note in particular the need to keep the plug tip within the correct temperature range during operation and how this is achieved by varying the length of the insulator. The outer shell is virtually the same irrespective of heat range.

 

about one month ago I put some Bosch iridium in mine, she been purring like a kitten.

 

Thanks Mikey, good info. NGK has a part finder on their website, so I will go ahead and use those. The only reason I am choosing NGK's is because I have used them on my previous cars and found no issues. I am sure all brands will work just find, I was just trying to be creative.

 

Opinion but I'd only go with colder plugs on a car that was not originally supercharged or one where you really cranked up the boost. I've only ever done that to reduce pre-ignition.

 

That's correct- an overheated plug tip can lead to pre-ignition.