Improving spark plug performance

[gunner54727]

I've read several postings about spark plugs (what brand, what type, what number, etc.) on here, but have yet to see anything about an old racer's trick to better perfomance and even reportedly longer life (although I haven't seen any longer life personally, theoretically you should need to regap more often as there is less surface area for spark and thus more erosion). The trick I refer to is to shorten the ground electrode so as to create an almost side gap style of plug. You file or grind the "wire" to shorten it enough to only reach the first edge of the center electrode ( be careful to keep edges sharp and free of burrs). You need to use a WIRE gap gage so as to set the gap to factory specs. The idea here is to keep the proper gap for the ignition system to work properly, and yet during the actual burn cycle of the plug the spark will flare much more and give a more complete burn. With more spark flare you can burn leaner mixtures also. There is a noteable change in performance in most cases, better torgue and even better fuel economy.

[WingAdmin]

I remember reading an article a while back on this, and had saved it for a rainy day. Here's what I had saved...it's from about seven years ago, so I have no recollection of where I got it:

One of the problems of buying the "premium" type spark plugs, is not only the initial cash outlay, but the hesitation to replace them at sooner than "normal" intervals. Hesitation to replace expensive plugs when attempting to diagnose an unknown problem is common and many times can waste a lot of time in the diagnostics procedure, especially when it turns out the plugs were the culprit.

First, obtain a high quality over the counter version that carries an economical price. Motorcraft and Autolite come to mind for their performance and safety features of inherently melting before the piston does. Then carefully shorten the electrode arm by taking a die grinder with a small cut-off wheel and remove a small portion from the end. *Do not* nick any part of the center electrode or porcelain! As seen in the photos below, nearly the entire center electrode can be seen from the bottom of the plug as compared to the standard version being completely shrouded from view. This modification will expose more of the generated spark to the combustion chamber, thereby more completely igniting the air/fuel charge instead of the spark being forced to propagate in a sideways direction and not directly into the majority of the combustion mix. This procedure of exposing the electrode is called "Side Gapping", and has been a well kept secret for many years in the racing circles. While some may debate the amount of Horsepower, Torque & Fuel economy increases, there is no disputing that side gapped plugs significantly improve spark propagation as well as reduce plug fouling and loading up, with no sacrifice to your wallet.

The sharper edges also encourages the spark to ignite quicker and stronger, much like striking an arc with a welder on an edge rather than a flat surface. However, there is one minor drawback, and that would be the center electrode will wear one side sooner due to the spark now being directed to one specific area on the plug edge, rather than a random path all around the electrode point. Even though the plugs may wear slightly quicker, since your home-modified plugs can cost up to four times less than that of "premium" versions, they can be more readily changed, leaving you with fresh new plugs during your engine's operation more of the time than with the costly premium versions.

As the photos show, the side gapped plug exposes more of the spark path to the open combustion chamber than the Standard version, as well as even the Splitfire® or Bosch+4® types. And this can be done to any of your favorite brands of plugs you already like, to make them better!

To gap the new plug, slide the feeler gauge in at a 45 degree angle to read the tightest clearance between the center electrode and the arm. Slightly tighter than OEM recommended gaps can be taken advantage of, measuring the actual space between the closest surfaces of the two electrodes. Reduce gaps by approximately .010". Closer clearances will yield the same if not more of the spark front, and at the same time resist the flame from being "blown out" when using Nitrous Oxide injection or supercharging. The closer "sharp edged" surfaces will more easily propagate the initial spark while the main mass of surface area being farther away, will increase the spark travel (volume). Re-gap periodically, as the accelerated wear on the electrode edges will increase the gap sooner.

NOTE: Side Gapping spark plugs has been the serious racer's secret since the early 60's. Only recently have major manufactures started producing this style of plug for mass production, but with unreproducible sophisticated designs, since if their expensive plugs looked like these, they would lose all their business to home mechanics copying that simple to do at home design. Experiment with different configurations.

This photo illustrates the shrouded standard type plug (red arrow) "squeezing" the spark sideways rather than downwards directly into the homogenized combustion mix in the cylinder such as the newly modified Side Gapped version does (yellow arrow). The Yellow graduation shows how much of the arm that was cut off:

This photo compares three types of plugs. Note the center electrode exposure the combustion chamber sees:

Cut the electrode arm off even with the edge of the center electrode. *do not* touch the center electrode or porcelain!

Carefully file the edges of the electrode arm to remove any remaining burrs, but keep the edges clean and sharp.

With a feeler gauge, set the gap at the narrowest point between the center electrode and the electrode arm. Reduce the gap by .010" than norm specifications.

How it works: The closer gap (1-Yellow) allows for easier ignition while the angled surfaces (2-orange) allow the ignited spark to grow in size to exceed that of normally shaped plugs. As the spark column flows along the electrode surface it grows outwards in size towards the combustion chamber and down towards the piston (3) creating a larger spark presence but with an easier starting spark for situations where more spark is needed, such as high compression cylinders, high rpm's and increased fuel conditions as well as preventing "spark blow-out" in nitrous and super/turbo charging applications.

The increased electrode exposure guides the angle of the flame front down towards the center of the combustion chamber promoting a faster, more complete and even burn thus increase power, performance and fuel mileage as well as reducing plug fouling:

[WingAdmin]

Incidentally, this isn't really a secret, as the same method of ignition is used in all light aircraft spark plugs:

[seabee_]

You should post this in the How To section or somewhere available. It's some good info on how to make a better spark.

[WingAdmin]

You should post this in the How To section or somewhere available. It's some good info on how to make a better spark.

I've done just that!

[gunner54727]

Thanks for elaborating on my original post. I actually saw this a couple years back on a Yamaha XS11 site. I also own one of those. It was a reminder of this "trick" that I had heard about when I was a young motorhead kid, some 35-40 years ago.

[virgilmobile]

I'll add just one more thing to this.
There is another tweak.Mark the direction of the gap end on the plug.
Run it into the block and check where it points to.
The ideal alignment is directly toward the intake valve.
I did this once on a gl1000.It took 9 plugs to get 4 that were close.
Did it help.????? I dunnow.The bike always ripped my shoulders loose anyways.

It's said it helps to ignite the fuel into the flow rather than as it's passing by.

[ottsum]

I'll add just one more thing to this.
There is another tweak.Mark the direction of the gap end on the plug.
Run it into the block and check where it points to.
The ideal alignment is directly toward the intake valve.
I did this once on a gl1000.It took 9 plugs to get 4 that were close.
Did it help.????? I dunnow.The bike always ripped my shoulders loose anyways.

It's said it helps to ignite the fuel into the flow rather than as it's passing by.

You could use shims to index a spark plug's orientation. Bombadier does this on their direct injected 2-stroke snowmobile engines.

[gold1200]

This side cut plug, isn't to secret. I used to cut my Champion L-88s, for my Baja bug, (I wouldn't buy a Champion plug now, If they were Free) But that was the trick thing then...... 1974.......... The bug was a 1788 kit, and it ran GOOOOOOOD....

[pippomaranga]

Incidentally, this isn't really a secret, as the same method of ignition is used in all light aircraft spark plugs:

Aircraft spark plug.jpg

ok i want to be different and posh does anybody knows if there is out there any aircraft spark plug that fits the goldwing 1500?

[WingAdmin]

ok i want to be different and posh does anybody knows if there is out there any aircraft spark plug that fits the goldwing 1500?

First off, they won't fit - they have a screw fitting on the end that screws the wire in place so that it can't vibrate off. Secondly, you REALLY don't want to buy aircraft plugs for your bike. For the price of a single aircraft spark plug, depending on the aircraft it was meant for, you could buy between 10 and 30 normal NGK plugs.

[pippomaranga]

ok i want to be different and posh does anybody knows if there is out there any aircraft spark plug that fits the goldwing 1500?

First off, they won't fit - they have a screw fitting on the end that screws the wire in place so that it can't vibrate off. Secondly, you REALLY don't want to buy aircraft plugs for your bike. For the price of a single aircraft spark plug, depending on the aircraft it was meant for, you could buy between 10 and 30 normal NGK plugs.

Ok....no posh or metrosexual sparkplugs for me at that price lol! but interesting topic!

[littlebeaver]

I have a wild idea, you boys tell me if you think it will work or what you think of it....In one of the first photo's above where it shows you cut the metal back to achieve this better arch, I see how it would but you stated that it would burn more to one side of the electrode thus wearing it out faster on one side, what if someone cut off the metal off an old plug welded it up to the opposite side of a new plug and had the two metal parts facing each other but cut back as suggested.....Would it work? a little farther down in the photo's you have one sorta what I'm talking about, the metal goes to the sides instead of over the top like I'm talking about.. I might have to try this...

[pippomaranga]

I have a wild idea, you boys tell me if you think it will work or what you think of it....In one of the first photo's above where it shows you cut the metal back to achieve this better arch, I see how it would but you stated that it would burn more to one side of the electrode thus wearing it out faster on one side, what if someone cut off the metal off an old plug welded it up to the opposite side of a new plug and had the two metal parts facing each other but cut back as suggested.....Would it work? a little farther down in the photo's you have one sorta what I'm talking about, the metal goes to the sides instead of over the top like I'm talking about.. I might have to try this...

They legalized marjiuana in texas too??

[littlebeaver]

Ha ha ha Very funny

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well that anwsers that question ha ha

[Kalamata]

Hi there,

I know that its been some time since someone posted on this topic, but I have some concerns about this modification. By cutting the electrode on the spark plug will increase the spark but if the piston comes to close to the spark plug at the time of the spark it may with time cause a perforation (hole) on the piston. I have seen several pistons with hole on it when using performance spark plugs and also high performance coils. I will recommend to probably try this on a engine that has been inspected before installing these modified spark plugs and after about 1k miles or so, open the engine and see if any visible damage has been done to the pistons.

[littlebeaver]

I'm glad I'm lazy and never changed the plug or modified it...I believe you...thanks for the information, if you saw something like that then I trust your word..

[NKYWinger]

kalamata: I'm not sure I agree with your theory; increasing the flame propagation should allow for a faster ignition across a larger area of the combustion chamber, therefore REDUCING the instantaneous temperature at any given point.
Does that make sense to anyone besides me

[Kalamata]

kalamata: I'm not sure I agree with your theory; increasing the flame propagation should allow for a faster ignition across a larger area of the combustion chamber, therefore REDUCING the instantaneous temperature at any given point.
Does that make sense to anyone besides me

NKYWinger: This may seem like a theory when dealing with this type of modification, a hole on a piston like the one that I've seen may prove my theory. Now, I would like to test the theory but not on my bike. Can we try it on yours and let me know? LOL

[NKYWinger]

I have been thinking about doing this - I'll let ya know!

[Kalamata]

Ok. Keep me posted. In the mean time I am trying to decide if I should make my bike into a trike with extra sitting space. My 8 yr. old daughter is asking me to make it so I can take her and her 11 yr. old brother for rides on weekend. We are a family of five with only two bikes and someone always has to stay behind.

[NKYWinger]

admin:
Did you do this to either of your bikes?? If so; any conclusions?
Inquiring minds need to know......

[organgrinder]

Has anyone looked at or tried the E3 plugs? did a web search and it seems to do what the modifications are discussing except it looks more like an airplane plug for autos.

[gunner54727]

I applied this modification to my 1500 shortly after my original post in 2012. Performance has improved slightly, as expected, but I have not noticed any fuel economy changes. I have borrowed a borescope and found nothing different on the inside. This works well for me without paying for special plugs.

[Old-Gold 76]

Hi All,

Back in the old days mercury marine had a surface gap plug for their outboard motors, I believe it was only used in thier electronic coils though. could this work?

Old-Gold 76