Turbo Spark Plug Gap

[greenguy103]

Hey guys,

I have a 1987 325i M20B25 with a turbo. my question is should I keep factory spark plug gap or would I need to run a wider or small one. I am new to turbo cars so just looking for some help. Thanks!

[Turbo_The_World]

The stock M20 spark plug gap is .28 I believe. Now some knowledge on spark plug gaps. Obviously a larger gap is going to be able to ignite more particles of fuel which results in a faster burn. The stock ignition system does a pretty decent job for how it's set up. The lower your gap the better chance you won't have spark blowout at high rpms and higher boost levels. So, if you're sticking with the single coil ignition, you want to have the largest gap, while still having optimal spark. Which for my turbo m20 is .24. I'm still getting some spark blowout at around 7k rpm, but I'm also running 20lbs of boost, so I'll be going with a wasted spark setup, so instead on a single coil, I'll have three coils running two plugs. What I'm getting at, is that if you're not getting spark blowout, leave it stock gap, if you are, tighten it up a little. Also make sure you're running a step colder plug. Pre-detonation is not fun.