for yrs i have been running plat plugs stock gap. recently i have upgraded about 50-100hp and switched over to one step colder copper plugs. lets say for argument sakes i have 350 hp what would be an ideal gapping. please no formulas im stupid. im currently gapped at .044
somebody told me i should gap at .030 please some sound advice and
will there be a difference in performance, thanks..

 

The general rule of thumb is reduce the gap by .004" for every 50 HP over stock (with a stock ignition system anyway).

 

For now I wouldn't go lower than .036. If you go too low there might not be enough spark to ignite the mixture.

 

It's not that there's not gonna be enough spark if the gap is too narrow, it's just that the air/fuel mixture might not combust as completely.

 

o.k so im gonna try .038 to play it safe. will the car run better or is
it just for safety. because the car seems to be a little rich at idle.
thanks...

 

I don't think there are any safety issues since plug gap doesn't affect afr, it's a matter of a few conditions brought on by forced induction that result in a compromise:

As large of a gap as possible is desirable so as to provide a sufficiently large ignition source for the fuel air mixture. But,

1. Increased turbulence in the combustion chamber can blow a spark out before it is able to ignite the fuel/air mix, causing misfiring, especially at high rpm. A reduced spark gap is used to reduce the likelihood of misfiring.

2. Increased compression, either due to raising the compression ratio in a NA engine or by forced induction, increases the dielectric strength of the fuel/air mix (Paschen's curve) in the spark plug gap. So either a higher voltage ignition system or a reduced plug gap is needed to induce a reliable spark.

All things considered, a forced induction engine usually benefits from a reduced spark plug gap. I think most people here are running about .034"-.038". I was running .036" for my 9 psi setup with a 3.25" pulley, but when I had my rev limit extended to 7200 rpm and went to a 3" pulley I reduced to .034". Haven't had any misfiring problems as far as I can tell, and power feels like it's all there.

 

thanks for the info. i'll reduce the gap and see what happens.

 

What's the gap for the 3.33" and 3.125" pulleys?

 

good question, also interested to know. I have a mevi with 3.125. I've been running stock platinum plugs for a week wit 50k miles on them about. I hope these plugs make a difference in performance since my old ones may be sh*tty.

 

that is a good question cause for yrs i have been running plat plus 4 sparkplugs with no problems with s/c and nitrous. but i just recently switched over to the copper bkR6E-11 ngk spark plug one step colder with 0.36 gap as recommended. and it works fine car idles smooth and no hard starts. with your set up i would try 0.38-0.36 unless you plan on running more hp that should do the trick.

 

should i be running the 2 step colder spark plugs? the 7's?

 

I am using the two step colder plugs with a 3" pulley, 7200 rpm rev limit, but Iansw is using just one step colder without any problems, and he is making a bit more boost than me with the 2.87" pulley, 7200 rpm.