I see some 2nd gen guys using all traiing plugs on their car. What are the advantages of using all 4 trailing plugs and disadvantages? Are there any good results using this set up? Im very interested in this.

 

The heat range of a plug is a measure of its ability to conduct heat away form the center electrode. A "colder" plug has a greater ability to conduct this heat away.

The use of a colder plug is advantagous when combustion temperatures and mass flowrates (both of which will put more heat into the plug) are great enough that the plug remains at a temperature above or near the ignition temperature of the air/fuel mixture as the next charge enters the plug area. This is a problem beause it can pre-ignite your charge which leads to higher combustion pressures and inturn detonation.

Why doesn't everyone run the coldest plugs made? Plugs also tend to foul when they are held at too low of a temperature.

In short: Run the coldest plug that won't foul (not always cost effective) or run the hottest plug that will not pre-ignite your charge.

Justin

 

heat ratings:
http://www.ngksparkplugs.com/techinf...000&country=US

 

So will i benifit from using the NGK 9's on all 4 on my NA? Does it benifit performance?

 

In short no advantages in a n/a, but here is a thread I started last year about it and my results of running all 9s. If you search you'll find this comes up every few months. Disadvantages are if you do alot of city driving they may foul.
https://www.rx7club.com/forum/showthread.php?t=382419

 

Oh fsho, thanks guys.

 

yep, no advantage in an n/a.

generally it works like this:

stock setup - 7's leading and 9's in trailing
200-300RWHP 9's all around
300-375WHP 10's all around
375+ needs to be heat range tuned, most people get away with simply running 11's


running too hot of a plug will cause ignition break up at high RPMs, as shown on many dynographs.

 

Colder ='s

Better for up top on anything.

Safer vs. detonation on turbo.

Not much for N/A.

Very general rule of thumb... 1 point colder for every 100 horsepower over stock heat ratings and stock horsepower.

stock HP=200

7 leadings 9 trailings

new horsepower 300

8 leadings 10 trailings


so forth and so on.



also good info....