C MAX

iTrader: (4)

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..

nismology

iTrader: (8)

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

pimpjuice

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

nismology

iTrader: (8)

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.

C MAX

iTrader: (4)

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...

Stephen Max

iTrader: (59)

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.

C MAX

iTrader: (4)

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

BlackCat

iTrader: (6)

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

meccanoble

iTrader: (22)

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.

C MAX

iTrader: (4)

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.

mighteatyou

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

Stephen Max

iTrader: (59)

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.