Spark plug heat ranges...

6 replies to this topic
  • Nashty

Posted November 02, 2006 - 08:54 AM


Anyone ever tried a colder or hotter plug for how you were riding / racing it?

What is the next colder range of plug? I'm installing nitrous and want to put a colder plug in it.

BTW, what is the best plug out there?

(Bike is a 2001 426)

  • grayracer513

Posted November 02, 2006 - 09:03 AM


The "heat range" of a spark plug refers to the amount of exposed porcelain on the nose of the plug. It effects how hot the plug stays by affecting the rate at which heat is conducted away from the plug tip to the head. It has no effect whatever on engine temperature until it gets so hot that it starts pre-igniting fuel, which can and does lead to detonation. Having the heat range correct lets the plug stay hot enough to stay clean and free of wet oil and fuel deposits, which would short it out, and cold enough that it does not cause pre-ignition. Decreasing the heat range of the plug will, for the most part, do absolutely nothing to aid performance in your dirt bike, and will probably cause more plug fouling, and shorten their useful life.

You should be running a CR8E, or an upgraded equivalent, such as those with platinum or palladium electrodes.

  • GONE1445

Posted November 02, 2006 - 06:32 PM


if your gonna run nitrous you should go one or 2 steps colder because when you hit the magic button it will raise the cylinder pressure and thus cause detonation

just my $.02

but I could be wrong I do know with a street car you should do this but dont know about with the 426

let me know how the nitrous works on your bike I have the same kind and was toying with the idea

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  • motodemon172

Posted November 02, 2006 - 07:38 PM


i would contact boondockers for more model specific information on plug heat range on nitrous equipped bikes. http://www.boondocke...q_files/FAQ.htm

  • grayracer513

Posted November 02, 2006 - 08:42 PM


Street cars are one thing, and dirt bikes antother. Cars drive around most of the time at a fraction of their output capability, and at fairly low RPM. Under those conditions, they need a hotter plug to keep the plug clean. This is a little less true in these days of extremely lean running smog cars than it once was, but is nevertheless still true. When you start running a CRX really hard with a bunch of mods, then you need to bring the heat range down some, bottle or no bottle.

Dirt bikes run harder to begin with, and already have fairly cold plugs. You may find that lowering the heat range isn't strictly needed on a NOx equipped dirt bike, but the only harm you will cause by doing it is a fouled plug.

  • Nashty

Posted November 03, 2006 - 04:40 AM


OK, now what would be the colder plug then?

CR7E ??

I use nitrous on my turbocharged drag car. It's 235" motor is pushing out 900hp now so I'm relatively comfortable with using it and know how to work with it.

But what's the consensus on best plug? I used an Iridium on my 250F and it fouled the plug pretty quick.

  • grayracer513

Posted November 03, 2006 - 09:22 AM


CR7E is hotter than a CR8E. Most foreign plug heat ranges work that way, which is typically opposite of American plugs.

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