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Author Topic: ..plug gapping..  (Read 2514 times)

wordslinger

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..plug gapping..
« on: April 13, 2010, 04:33:23 PM »
..so, i'm running a NGK C8HSA...

..service spec for the gap is .6-.7mm...

..what are the determining factors for gap specs...

..what happens if it's less, and what happens if it's greater..

..got two new plugs comin' in today...


peace
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zombie

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Re: ..plug gapping..
« Reply #1 on: April 13, 2010, 08:40:37 PM »
The output of the coil, and the built in resistor inside the plug determine the gap. Too far, and the spark gets erratic, As the compression increases in the cyl. the spark has a harder time finding a place to dissipate. Too close, and there is not enough time to ignite the mixture. To cover all the bases EVERY I.C. engine I own/have ever owned gets a high output coil, and where I can NON resistor plugs. The next thing to the better plugs is solid stainless Ign. wires. You can get a coil on ebay for $19.95. Look for the GY-6 hi performance coils. Just un-screw, and re use your factory boot as the hard plastic ones don't last.
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wordslinger

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Re: ..plug gapping..
« Reply #2 on: April 13, 2010, 08:42:54 PM »
..cool..i always wondered...now i know!!!
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Dark13

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Re: ..plug gapping..
« Reply #3 on: April 14, 2010, 02:38:43 AM »
i was wondering about that myself as well

so if you switch coils do you need to change plug types?

and what is the benefit?

i would imagine that a better spark would mean that the fuel is burned more completely and therefor you would have more power am i right or is there more to it?
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Calothrix

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Re: ..plug gapping..
« Reply #4 on: April 14, 2010, 02:58:20 AM »
Zombie, why the non-resistor type plug?  Thanks!
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zombie

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Re: ..plug gapping..
« Reply #5 on: April 14, 2010, 05:20:04 AM »
Just change the coil will improve the spark you have on the same plug. Hotter (by hundreds of degrees) and longer (by milliseconds) it improves everything in the engine! With that you now have the option of using different types of plugs more efficiently, and still be sure of a fair start at ignition. I have run seven or eight different plugs to find the ones that work best in my set up. I have been running NGK BR7HS10 gapped at .35 for a year and change, and replace the about 4 times a year. I could never run that plug, and gap with the stock coil. In fact if it started it would surprise me. As for the NoN resistor plugs; If you carefully break any plug with an "R" as the second character ( BR/HR ) you will find a TINY gauge wire soldered to an even tinier resistor. That is soldered to the tip coming out of the insulator. The non resistor type (b7hs10) have a solid electrode thru the entire plug. The benefit is obvious. Same for stainless wire vs Graphite core. More voltage = hotter spark.
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wordslinger

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Re: ..plug gapping..
« Reply #6 on: April 14, 2010, 11:55:50 AM »
..this is a very informative thread....

 8)
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OldGuy

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Re: ..plug gapping..
« Reply #7 on: April 14, 2010, 01:42:08 PM »
Sorry but I can't agree. Once the spark ignites the fuel it has done all it can do. A "hotter/bigger" spark will not improve performance or fuel mileage.

Another hint on plug gap; A wider gap means easier starting (longer spark & better chance of ignition) and a narrower gap means higher revs are possible (has to do with dwell time).
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OldGuy
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wordslinger

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Re: ..plug gapping..
« Reply #8 on: April 14, 2010, 01:48:48 PM »
Quote from: OldGuy on April 14, 2010, 01:42:08 PM
Sorry but I can't agree. Once the spark ignites the fuel it has done all it can do. A "hotter/bigger" spark will not improve performance or fuel mileage.

Another hint on plug gap; A wider gap means easier starting (longer spark & better chance of ignition) and a narrower gap means higher revs are possible (has to do with dwell time).

...explain to me a lil more about the higher revs....we all need that on these A50s...

 ;D
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zombie

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Re: ..plug gapping..
« Reply #9 on: April 14, 2010, 04:43:24 PM »
My point being, if you have a marginal mix, High humidy or rich/lean conditions a hotter spark from a larger gap will stand a better chance at ignition and an even burn thru the chamber. I'm not trying to say the spark runs the engine better, more like good ignition is the key to a better running engine. A narrow gap will fire faster (milliseconds) but not create higher revs ( for slingers ?)
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OldGuy

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Re: ..plug gapping..
« Reply #10 on: April 15, 2010, 01:08:09 PM »
Quote from: wordslinger on April 14, 2010, 01:48:48 PM
...explain to me a lil more about the higher revs....we all need that on these A50s...

 ;D
I knew this question was coming. The key word is "possible". Changing the gap will not in itself give you more RPM's. Basically, the reason for this is that it takes less voltage jump a short gap than a long one. The system doesn't need as much time to build up sufficient voltage to fire the plug.

A word of warning about setting the gap wide. Since the electrodes erode with use the gap gets wider over time which may cause mis-fires. Since I'm a "less work is better" kinda guy I always set the gap on the short side of the spec.
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OldGuy
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wordslinger

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Re: ..plug gapping..
« Reply #11 on: April 15, 2010, 01:15:35 PM »
..cool..i think i have the concept...

..i gapped one plug at .6 and one at .7 and i could tell no difference...

...i do think i'll look into a performance coil though...

..thanx guys!
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