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Spark plug heat range question

Old 01-16-04, 05:03 PM
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Spark plug heat range question

I have an oval track race car.....an 82.....and i was wondering which heat range would be best for me as i stay up in the upper RPM range.

BR9EQ14 or BR8EQ14 or BR7EQ14

either 7, 8, or 9 heat range

Thanks
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Old 01-16-04, 05:11 PM
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arent those the stock plugs?
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Old 01-16-04, 07:18 PM
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higher the number=lower the heat range. I would try to find some 10's or 11's, but I wouldn't run anything hotter than a 9 in any racing rotary.
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Old 01-16-04, 10:56 PM
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i didnt quite understand that last post......mabye someone could fill me in on even what a heat range is.
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Old 01-17-04, 09:30 PM
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all spark plugs have a "heat range". for simplicity it is how hot the spark gets. at higher rpm's and at higher intake air temps(like turbos) you want a "colder" spark plug because it does not take much to get these mixtures ignited. to hot a plug can cause detonation and serious engine damage. on a street car I would run what the manufacturer recomends, but for track only cars that will always be run at the high end of the rpm curve colder is better. all race turbo cars can benefit from a colder plug. the NGK plugs are kind of backwards as the number increases the "heat range" goes down. so a 7 plug is "hotter" than an 11. the third and some time fourth digit in most NGK plugs is the heat range. I hope this makes sense.
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Old 01-18-04, 02:21 AM
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Yes that made perfect sense thank you very much for your help..... i think ill get a 9
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Old 01-18-04, 06:37 AM
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You can run lower heat range >9.
The problem is higher heat range is hard to start when cold, and you could foul them easily.
What you have to do is have two set of spark plugs.
So you need to use higher heat range <10 for cold start. After engine warm up, switch to lower heat range.
So you could run 11 and start the car with 9 or 8.
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Old 01-18-04, 09:35 AM
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Originally posted by reza
You can run lower heat range >9.
The problem is higher heat range is hard to start when cold, and you could foul them easily.
What you have to do is have two set of spark plugs.
So you need to use higher heat range <10 for cold start. After engine warm up, switch to lower heat range.
So you could run 11 and start the car with 9 or 8.
That sounds like a hastle, but that would work. There seems to be so little time to do that kind of stuff like that at the track. The last event I was at the track opened at 7:00 am and we had to be on grid at 8:00 am, and go thru tech as well.

I run about 130:1, 2 cycle oil in my FB with a 12a. I would be worried about fouling out in grid with anything over a 10 rated plug.

Anyone running 10 or higher plug and running high ratios of pre-mix?

Last edited by cpa7man; 01-18-04 at 09:38 AM.
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Old 05-08-13, 10:00 AM
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I'm running high premix on high compression and the cold plug starts cold but is a bitch to start after its hot I would recamend 7 heat range for leading and 8 for trailing but I have an fd bridge port and 24psi boost two different cars and set up
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Old 05-09-13, 12:41 AM
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Im running roughly 50:1 premix (since it comes in nice premeasured bottles) and have NGK 11.5 race plugs for after its warmed up (generally Ill just throw them in after practice)
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