Check out those NGK links up above in this thread. General speaking, the more mods you have/boost you run/power you make, the higher the heat range you want to run. ie, 7s and 9s are fine for stock, all 9s are good for slight mods, 10s and up for higher boost, like 17 psi. Each FD is different, so the jump from 9s to race plugs (10+) is a ballpark figure. I can tell ya I have always had race plugs when making over about 350 rwhp.

The 7s will help with startup, and will not foul out as easily, esp when on an 'engine break-in' kind of driving schedule. Vice versa, the race plugs don't like low rpm, stop and go traffic kinda stuff.

Rich

 

Also, I don't think running four 7s is necessary....stock is 7 leading and 9 trailing, so I would consider that the default.

 

But on page 4 of NGK's guide it states: As compression increases, a colder heat range plug, higher fuel octane, and careful attention to igni-tion timing and air/fuel ratios are necessary. Failure to select a colder spark plug can lead to spark plug/engine damage. The whole guide says that a higher heat plug will lead to detonation. Now I'm shooting for 400hp on BNR 3's, what plug is the best?

 

Higher numerical heat range means a colder plug. A "10" is colder than a "7" plug. You want "cold" plugs in a "hot" engine.

-Max

 

Ok, that makes sense. What screwed me up was the first post. He said colder and run 7's.

 

I can see where I would have misled ya as well....."the higher the heat range"

sorry about that

 

I'm running 10.5s right now, and have no cold start issues in the Sac area. Of course, I started running them in the spring and summer, so I won't know until winter how the cold start goes. If it still starts easily in Dec and Jan, then I'm going to go to 11s and 11.5s. Basically I want to run as cold a plug as I can without fouling. Mazdacomp sells NGKs all the way to a 13, but I have a feeling that will not start in the winter. I'm hoping to try the 11s this winter, early next year, but only if my 10.5s don't have cold start issues. I may end up running one step colder plug during the summer vs. the winter once I find just how cold I can go.

BTW - The higher number/cooler plugs help wick away heat from the combustion chamber, which is very healthy for our motors. Might be common knowledge, but the NGK website has some good info on this.

The gas in Kalifornia is just terrible, and leaves lovely deposits on plugs with our rich running modded singles. I'm only getting about 5K out of a set of 10.5 plugs, which makes for expensive plug changes, but you have to pay to play.

Beast

 

I wish more people on this board understood that simple concept.

Rich

 

Car won't start in cold temps with the 13's. I should qualify that with what I mean by cold, anything even approaching freezing temp. I remember to run a couple times in late fall I had to put in 11's or warmer to get the car started and warmed up, then shut down and reinstalled the 13's while the engine was still warm, and yes the 13's really do foul easily.

Kevin T. Wyum

 

yeah theres no way of getting around this but people try

 

I bought the b10egv's yesterday. Have fun putting them in my car. Hopefully James will no what to do. Keep me posted on everything that's going on. I wish I was there for the tuning. Have fun. I'll meet up with you on the 9th of October for the Gator game.

Aldo