chiminoid

i've done my searching and researching... just wanted to confirm.

NGK Spark Plugs-
Leading: 7
Trailing: 9


i'm gonna be running with just a DOWNPIPE AND INTAKE for a good while (3 months at least) and i wanted to know if leading 7's and trailing 9's sound right for spark plugs. from what i've read, this seems to be the best setup for a near stock FD. this will mainly be city driving but of course i'll hit the highways and byways a few times a week

they're gonna be NGK's but should i go copper, platinum, iridium ?


thanks
-chim

Husemoller

What exactly does that mean anyways?

maxcooper

The number is the plug's "heat range". For a given set of conditions, a plug with a higher number will run cooler (i.e. the temp of the plug will be cooler). As you increase horsepower, you need colder plugs to extend their life and perhaps avoid having the too-hot plug ignite the mixture prematurely. The rule of thumb is that a hotter engine needs colder plugs. On the other hand, if the plug runs too cold, it won't burn off deposits which will lead to "fouling". Fouled plugs cause hard starting and lower horsepower. So, the goal is to get a plug that is the "right" temp -- not too hot or too cold.

BUR-7EQP leading and BUR-9EQP trailing are the stock plugs, and they work well for many cars; even ones with a number of mods. I think they would be a good choice for your car, chiminoid. The "P" at the end of the model number indicates that they are platinum. The same numbers without the "P" are the non-platinum version of the same plugs. Leading plugs typically wear out faster (since they fire twice as often), so if you were trying to keep costs to a minimum, you could run BUR-7EQP leading and BUR-9EQ trailing and change them all at the same time.

Iridiums are considerably more expensive, and I am not really sure where to get them or what heat ranges they come in. I did see an interesting comparison between a number of plugs for the SVT Lightening truck and the Iridium plugs for that application seemed to offer a very substantial reduction in the number of misfires. The test conditions were kind of suspect, but it still seems like a positive endorsement for those plugs. Remember that it wasn't a test of the specific plugs you'd use in a rotary, however. It sounds like they should last a long time, but I haven't heard one way or the other.

-Max