After a few hrs reading threads about recommended spark plugs for FI, i decided to go with the NGK 7405.

I was unable to find any concrete info on gapping. Ppl seem to gap from ranges .34 - .44.

I have the CTSC on my 03 and will be running a 7psi pulley soon. Any thoughts on gaps?

 

i believe xviper said .040 for NA, .035 for FI

 

All those gaps should work. The higher the pressures in the combustion chamber the smaller the gap need to be. At 7 lbs boost a 0.035 or 0.034 should be great. With 14 lbs boost I'm running 0.032.

If your gap is too big you will get a misfire.

 

that's all!

sideways, you are super helpful, as always. i'll buy u a beer some time

 

I have the same set up and I have mine at 35 I believe.

 

I would like to add to this. you want the biggest possible gap you can get without a missfire. this way you will burn the fuel properly and get the most power by fully burning the fuel for that cycle without misfiring.

its not just a matter of going a tiny gap without misfiring. be greedy and go for the largest gap you can without blowing the spark out.

 

Hmmm....

So by the time you figure out that your gap is too big you've already misfired on 1 or all cylinders..... No thank you.

Tuning with spark plug gap is NOT what I would suggest.

JMO.

Tim

 

why not?
you think a few misfires is going to cause dents in the s2k's forged pistons? s2k's have knock sensors anyway it'll automatically retard the timing.
This is coming from experience. I had a 12 second s13 and getting the right sized gap is important.

 

moving to FI

 

what are the NGK 7405 series? all my research pointed me towards the 7173 copper racing plugs...