Been doing some reading up on spark plugs, and the consensus is to go with one step colder plugs when boosted, as probably most of you already know. Very few people say two step colder, but I'll get into that later....

I remember reading back, I mean way back when I joined the org, that when switching from platinum plugs to copper plugs, don't go one step colder, because the copper plugs are one step colder by default. If you did go one step colder on the coppers, you would actually be two steps colder. Any truth to this? I searched and reread all the old spark plug threads, but couldn't find what I was looking for. I'm planning on getting the copper NGK BKR6E-11 and gap them to .036.

Also, most people agree that copper holds a better spark for boosted applications. Some argue that that there's no difference as far as performance, it's simply a matter of service life. What is the truth? Any studies/tests which prove one or the other?

And then there's irridiums, the ultimate spark plug (so I've read). I've read it's the best for retaining its spark and not blowing out under extreme boost, but aren't they more expensive than platinums? At 10psi, I'm not exactly pushing the envelope, so I figure coppers would be the way to go at $1.80 each. I also like the idea of changing them often, just like changing the oil, so I feel everything is running at its full potential. Thoughts?

 

Iridiums are much more than coppers, but slightly less than platinums. They are about $6 a piece, vs. $1-$2 for coppers and $9 for platinum. Coppers, from what I have heard are better for boost than platinum. Iridiums are supposed to be better still, but if it is worth it to you is the question.

Heat ranges (within NGK's naming scheme) should be consistent no matter the plug element.

2 step colder is for boost + n2o, or a whole lot of either one (to the point when internals need to be changed almost). If you just have any normal Maxima level of boost or N2O then 1 step colder is fine.

 

are there potential side effects from not putting in one step colder plugs? such as engine damage or something like that.

 

Good post, My friend was arguing with me the other day that i'm really stupid for running 12psi on my supercharger with bkr6e-11 coppers. He argued that I need 2 step colder plugs. WTF? I had no reason other than "I read it on the org". Can you guys elaborate in addition to the OP.

 

No engine damage, it just takes more heat away from the combustion chamber. You may lose a little power since the pressure is not as high, but no one would really need it NA. You could advance the ignition timing to compensate, but unless you had to run colder spark plugs I wouldn't.

12psi SC should be fine with 1 step colder, but I would be a little weary of the ignition timing over 10psi if you have not addressed that and make sure your fuel delivery is in good shape. You are not seeing high boost as much as a turbo anyway, so it should not be too big of an issue.

 

Well, I have the JWT ECU . We all know how timing is with this POS. LOL. Thanks for the response SPiG. Sorry to hi jack, on to the OP?

 

Here's an approach to determine if you need 2 step colder plugs TJ:

1. Install one step colder plugs and properly tune your fuel delivery curve so that you car is not running too rich or too lean.

2. After 200-300 miles, remove the one step colder plugs and install 2 step colder plugs.

3. Drive with two step colder plugs for 200-300 miles. Then remove one of the spark plugs and check for a residue of carbon (black stuff on insulator).

If there is fouling (residue is present) then remove the 2 step colder plugs and go with the one step colder plugs. If no fouling is present, then leave the 2 step plugs in as they are perfect for your supercharged application.


As a general rule of thumb, for each 8-10psi of boost, you want to run spark plugs that are 1 heat range cooler. The trick is to find a spark plug that runs cool enough to support a supercharged environment but also burning hot enough to prevent spark plug fouling.

Also, the gap of the spark plug should be reduced about .004 for every 50HP increase. This is why a lot people gap their plugs around .036 The range for us is between .034 to .038

.044 -.008 = .036
OEM + 100HP gain=new gap

 

Thanks for the info!

 

Id never run anything but coppers on a blown engine. I run 2 steps colder on my B13. Melting plugs on a dyno isnt fun.