Spark Plug Gapping

0face · Post by **0face** » Wed Oct 23, 2013 1:38 pm

I just did a spark plug change on my car. I had to gap all the plugs as they didn't come with the recommended gap. It got me thinking, what is the difference in gap size purpose. I'm assuming the recommended gap is to create the best combustion for the cylinder size and fuel mix, duh, right?

But say the gap recco was .44 and I stick .55 in. what will that do? (Besides cause WWIII). It seems like the bigger spark, more fuel/air burned? If not then why those split spark plugs?

HotRodZilla · Post by **HotRodZilla** » Wed Oct 23, 2013 2:05 pm

Because nobody likes a gap that is too small or too big. The gap needs to be just right.

Seriously, it has something to do with the amount of power required to create the spark and fire it across the gap. Too small, and the spark is too small. Too big, and maybe the plug doesn't fire at all. I have often wondered what the real tolerance is. Say the gap on the plug is supposed to be .44. Is .43 too small, or is it ok until .39? Is .45 too much, or is it ok until .55? This why we should just go back to horses and bicycles.

0face · Post by **0face** » Wed Oct 23, 2013 2:51 pm

HotRodZilla wrote:Because nobody likes a gap that is too small or too big. The gap needs to be just right.

Seriously, it has something to do with the amount of power required to create the spark and fire it across the gap. Too small, and the spark is too small. Too big, and maybe the plug doesn't fire at all. I have often wondered what the real tolerance is. Say the gap on the plug is supposed to be .44. Is .43 too small, or is it ok until .39? Is .45 too much, or is it ok until .55? This why we should just go back to horses and bicycles.

Then we'd argue about what kind of Oats to feed Wheaton's glue factory reject horse and Bust would never leave the barn.

HotRodZilla · Post by **HotRodZilla** » Wed Oct 23, 2013 2:52 pm

OMFG...That is so funny only cuz it's so true!!

wpbfjr · Post by **wpbfjr** » Wed Oct 23, 2013 2:53 pm

my guess is flame front ignition temperature. for my guess to be valid, a split plug would then have to have a smaller gap than recommended for standard plugs. where's jestal when you need him?

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bungie4 · Post by **bungie4** » Wed Oct 23, 2013 3:10 pm

Mind the Gap

http://thechive.com/2013/10/21/mind-the-gap-35-photos/

wheatonFJR · Post by **wheatonFJR** » Wed Oct 23, 2013 3:20 pm

bungie4 wrote:Mind the Gap

http://thechive.com/2013/10/21/mind-the-gap-35-photos/

The link above you want me to open isn't really about sparkplugs...now is it?

Or does the Chives have an automotive technical section?

clocklaw · Post by **clocklaw** » Wed Oct 23, 2013 3:44 pm

wheatonFJR wrote:The link above you want me to open isn't really about sparkplugs...now is it?

Wheaton....it is not really about sparkplugs....I checked from my desk at work. I was very thorough and looked through the entire page (and a few of the links) to be sure. The subject at the other end of that link is, in fact, about "factory air".

Post by **extrememarine** » Wed Oct 23, 2013 6:17 pm

The basics.

A little deeper.

and a little wiki.

Chuck35 · Post by **Chuck35** » Wed Oct 23, 2013 9:18 pm

0face wrote:I just did a spark plug change on my car. I had to gap all the plugs as they didn't come with the recommended gap. It got me thinking, what is the difference in gap size purpose. I'm assuming the recommended gap is to create the best combustion for the cylinder size and fuel mix, duh, right?

But say the gap recco was .44 and I stick .55 in. what will that do? (Besides cause WWIII). It seems like the bigger spark, more fuel/air burned? If not then why those split spark plugs?

If the gap was not right, you either got a cheap plug or the wrong one. NGK and ND plugs are usually spot on and they are packaged with a sleeve around the threaded end to maintain that gap during shipping and storage.
I have found over the years that best results are gained by using plugs manufactured in the same country as the engine. Don't use Autolites in your Toyota.
If the gap is to small, you don't have enough spark to ignite all the fuel/air mixture in the available time. If it is to large it will place a higher load on the coil as well as the insulating capability of the plug wire/boot.

rushes · Post by **rushes** » Wed Oct 23, 2013 9:22 pm

bungie4 wrote:Mind the Gap

http://thechive.com/2013/10/21/mind-the-gap-35-photos/

Be fun to check those with my feeler gauge.....

Bust · Post by **Bust** » Wed Oct 23, 2013 9:55 pm

The gap in me anus got over-sized once.. I shit down my leg for a week.

I had an 02 blazer in my garage a few months ago that was running rough, dude said it was down on power and also suspected transmission was bad due to jerky shifting.
207000 mile plus a few. Recommended plug gap.. 60 thousands actual gap average on OEM original plugs? 155 thousands.
I GUARANTEE before the 'electronic age" this vehicle would have never even started.

Today's electronics are a good thing for dip shits like him.

HotRodZilla · Post by **HotRodZilla** » Wed Oct 23, 2013 10:13 pm

Bust wrote:The gap in me anus got over-sized once.. I shit down my leg for a week.

I had an 02 blazer in my garage a few months ago that was running rough, dude said it was down on power and also suspected transmission was bad due to jerky shifting.
207000 mile plus a few. Recommended plug gap.. 60 thousands actual gap average on OEM original plugs? 155 thousands.
I GUARANTEE before the 'electronic age" this vehicle would have never even started.

Today's electronics are a good thing for dip shits like him.

So you're saying Don's feeler gauge was too big, and that guy had 207,000 miles on a set of plugs?

I'm betting your feeler gauge was too small to properly gap those plugs. Sheesh!

Bust · Post by **Bust** » Thu Oct 24, 2013 11:57 pm

HotRodZilla wrote:
Bust wrote:The gap in me anus got over-sized once.. I shit down my leg for a week.

I had an 02 blazer in my garage a few months ago that was running rough, dude said it was down on power and also suspected transmission was bad due to jerky shifting.
207000 mile plus a few. Recommended plug gap.. 60 thousands actual gap average on OEM original plugs? 155 thousands.
I GUARANTEE before the 'electronic age" this vehicle would have never even started.

Today's electronics are a good thing for dip shits like him.
So you're saying Don's feeler gauge was too big, and that guy had 207,000 miles on a set of plugs?

I'm betting your feeler gauge was too small to properly gap those plugs. Sheesh!

Stuff a meat whistle in it cocknose

beemerdons · Post by **beemerdons** » Fri Oct 25, 2013 8:54 am

Bust wrote:
HotRodZilla wrote:
Bust wrote:The gap in me anus got over-sized once.. I shit down my leg for a week.

I had an 02 blazer in my garage a few months ago that was running rough, dude said it was down on power and also suspected transmission was bad due to jerky shifting.
207000 mile plus a few. Recommended plug gap.. 60 thousands actual gap average on OEM original plugs? 155 thousands.
I GUARANTEE before the 'electronic age" this vehicle would have never even started.

Today's electronics are a good thing for dip shits like him.
So you're saying Don's feeler gauge was too big, and that guy had 207,000 miles on a set of plugs?

I'm betting your feeler gauge was too small to properly gap those plugs. Sheesh!
Stuff a meat whistle in it cocknose

Hey 'Zilla, go take a flying f@$k at a rolling Armadillo eh Chingasa!

clocklaw · Post by **clocklaw** » Fri Oct 25, 2013 9:19 am

beemerdons wrote:Hey 'Zilla, go take a flying f@$k at a rolling Armadillo eh Chingasa!

Bust wrote:Stuff a meat whistle in it cocknose

I think you struck a nerve....lol

wheatonFJR · Post by **wheatonFJR** » Fri Oct 25, 2013 10:06 am

clocklaw wrote:
beemerdons wrote:Hey 'Zilla, go take a flying f@$k at a rolling Armadillo eh Chingasa!

Bust wrote:Stuff a meat whistle in it cocknose
I think you struck a nerve....lol

That's what HE said!

HotRodZilla · Post by **HotRodZilla** » Fri Oct 25, 2013 6:42 pm

wheatonFJR wrote:
clocklaw wrote:
beemerdons wrote:Hey 'Zilla, go take a flying f@$k at a rolling Armadillo eh Chingasa!

Bust wrote:Stuff a meat whistle in it cocknose
I think you struck a nerve....lol
That's what HE said!

More than once I hear. P-U-K-E!!

silverback · Post by **silverback** » Sun Oct 27, 2013 7:21 pm

Spark plug gap is a trade off between how much spark and how long it hangs around. Smaller gap, longer time, lower voltage. Larger gap, shorter time, higher voltage.

Higher voltage causes more wear on coils and plug electrode/anode. Also takes longer "soak" time on coils. CDI rectifies that partially.

Lower voltage obviously means less available spark to fire the fuel air charge.

Its all a trade off and there is definitely a sweet spot. Newer tech makes the sweet spot wider.

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0face · Post by **0face** » Sun Oct 27, 2013 8:45 pm

silverback wrote:Spark plug gap is a trade off between how much spark and how long it hangs around. Smaller gap, longer time, lower voltage. Larger gap, shorter time, higher voltage.

Higher voltage causes more wear on coils and plug electrode/anode. Also takes longer "soak" time on coils. CDI rectifies that partially.

Lower voltage obviously means less available spark to fire the fuel air charge.

Its all a trade off and there is definitely a sweet spot. Newer tech makes the sweet spot wider.

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Now that's an answer!

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