Spark plug gaps - simplified

[MrGrumpyman]

I've read lots of stuff on here about plug gaps, and reducing them seems to be the way to go, so, before I get me sockets out I'd just like to ask a simple question.......my plugs are standard gap, will I see any benefit in closing them up a bit? I'm thinking about long term benefits, i.e. reducing possible damage to coil packs etc, or should I leave them as they are, on an "if it ain't broke, don't fix it basis"?

I have a Nissan X-trail, 2.5 litre, regular LPG and normal service where plugs are changed each time, roughly every 10K miles. I tend to plod along with my driving, keep to lowish revs, I don't cane it at all, so it's pretty low stressed.

[Gilbertd]

By closing the gaps you will put less of a strain on coil packs as the voltage doesn't need to be as high to get the spark to jump the gap.

[MrGrumpyman]

By closing the gaps you will put less of a strain on coil packs as the voltage doesn't need to be as high to get the spark to jump the gap.

Hi Gilbert, thanks for that. Is there a magic figure to reduce the gap by? or is it trial and error?. The standard gap is 1.0 - 1.1mm, or in my language 39-43 thou. 30 thou has been mentioned in other posts, should I give that a whizz to begin with?

Cheers

Neil

[Gilbertd]

Back in the old days of points and condensor ignition systems, 25 thou (0.63mm) was the standard for plug gaps but I used to drop to 20 thou (0.5mm) on racing motorcycles. Using an old style engine diagnostic machine you used to see the voltage at the plugs. An ignition system in good condition with new plugs would normally run at around 25-30kV but as the plugs eroded so the gap opened up, it would rise to 40+kV. It is this that puts extra strain on the coil packs on a modern system, coil packs being less robust than an old fashioned oil filled ignition coil.

So try 0.6-0.7 and you won't go far wrong.