Picture of Save Gas And Incerase Horsepower By Side Gapping Spark Plugs
Side gapping spark plugs has been use in racing for years to increase horsepower by unshrouding the spark thus allowing the flame created to propagate faster resulting in a more complete burning of the fuel/air mix. Many manufacturers offer plugs deemed racing plugs that are side gapped but at inflated costs. By doing it yourself you can use a cheap .99 cent plug to save money and increase horsepower.

Step 1: Cuttting ground electrode

Picture of Cuttting ground electrode
Using a dremel with a cutoff wheel or a hacksaw you will need to cut the ground electrode even with the edge of the center electrode. You need to be careful not to hit the center electrode or the porcelain.
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picbuck7 years ago
But...if it were that easy to increase mileage and horsepower...wouldn't the manufacturers be doing it? And bragging about it in Superbowl ads? Well...just a thought.
galeb picbuck3 months ago

Follow the money, auto companies and oil companies have the same board of directors or related ones.

Not necessarily, commercials(especially those showcased during the superbowl) are dictated by trends and marketing plans. There have been plenty of technologies that have gone basically unnoticed by the general population simply because they are unpopular or don't fit into the "American Way"(basically quick/easy/cheap).
My reference to the Superbowl was, of course, a metaphor. Meaning a manufacturer who comes up with a better way tends to shout the news from rooftops (also metaphorically). On a more basic level, the media--both print and electronic--have long since fallen into bash-America mode. But the view that "they" (any they) are better than America is mistaken. Europe curses us for what they call our effete central heating and air conditioned cars. But we don't want to keep such things to ourselves, we want Europeans to have them too. Compare the two ethical stances, and decide which is better. While in the East, Japan and China--among others--have a more productive view. They want to be us. The American Way can be very simply stated: you're as good as the next guy, and you can take your shot the same as anybody else. If anybody can find fault with this view then they are, as far as I'm concerned, welcome to their opinion. That's another thing about the American way: you can have your opinion, you can state it as loudly as you like, and all Americans band together to protect your right to do so.
Cjern4 months ago
Ever try 100% pure acetone? I've read some stuff on it and tried it and noticed a crazy increase in mpg and some power. 5oz to 10 gallons. Thought it was BS so I tried it on my wife's RDX and couldn't believe the difference. Had it in the dealer and asked them to check the fuel system while it was in there and they said there was nothing wrong with it. I just wanted to be sure. Also a buddy of mine tried it on his Dodge pickup with I think it's a 5.7 hemi. He said his mpg went up 6mpg and said it seemed a lot smoother. It's only said to help the gas vaporize better so it ignites faster and more complete. Just throwin that in to see if anybody's ever tried that? Want to try it on my car to see if I notice a difference. Didn't mean to change the subject.
The only thing side gapping will do is change WHERE the burn begins - not how much or how fast or how completely the mix burns. If anything, increasing the gap would theoretically increase the speed of the burn because you're igniting more fuel initially vs a shorter spark. Newer plugs are proven to burn better because they are producing a bigger (fatter), hotter spark. My question has always been - and why I found this - what happens when you simply increase the gap.
stevem31 year ago

Side gapping has been used going back to the First Days of Indy Racing. The Grandson of 1st Indy Winner in 1911 Ray Harroun (Bill) use to come to the Circle Burner Motorcycle and Sprint Car Races locally. He mentioned numerous times when racers were doing plug checks or changing heat ranges about how they side gapped their Sparkplugs back in the day.. If it didn't work then nobody would have continued doing it. It's more than a 100 years later and it's still being used....So There!

People back in the day also thought the earth was flat until someone came up with some hard evidence to disprove that ;-) Lots of "experts" do lots of things in lots of fields for long periods of time that are complete BS. I'm a Dr - there are so many medical myths that Drs and nurses get passed on and will never stop - they're complete BS and have no fact basis but they still do it and it gets passed on!! Ever read on an ER direction sheet to keep your stitches "clean and dry" - absolute worst thing to do for any wound!! Keeping it dry CREATES a much bigger, nastier scar and delays the healing process by at least 40%. We base our decisions on hard facts - not just because someone claims it works and its being done by everbody ;-)
cowfy10 months ago

plus a 5 gas sample before and after should give black and white indication.

cowfy10 months ago

i am not groking this.why can't any evidence be gathered.it shouild be a simple matter.just compare burn time before and after cutting the plugs.does that make sense?

bmj67 (author) 7 years ago
If it didn't work then why would just about all spark plug manufactures offer the plug in one form or another. Here are a few links to some of the plug makers.




Those are just a few manufacturers but they all look just about the same as what my modded plug looks like with the exception of the bosch platinum 2.
LasVegas bmj677 years ago
Those plugs are designed/intended for single use. They are replaced between every race. They're also made using platinum or nickel to handle the higher heat. Standard plugs use steel. The last (Bosch) plug actually has more than double the spark area of a standard spark plug! That one I might consider experimenting with.

@LasVegas, The only racers that use this tec is Pro Stock and they do not remove the plugs. They run them for the entire weekend All of the other Pro classes use some form of power adder and tune the car based on in part what the plugs look like.Also note they are making around 1600 HP on motor only and every little bit counts.

Im not sure about the whole one use thing, i have a 02 chevy SS pickup that i have done extensive work to and i use only bosch platinum in it and i only change my plugs once a year (not every time i run the truck) i never had any problems with them
bmj67 (author)  LasVegas7 years ago
Where do you see that it says they are to be replaced after every race. Also racing engines take more stress than a normal engine so theres not a big need for the more exotic metals in a stock engine. Spark plugs Do Not produce heat read for yourself HERE that is ngk's site.
bumsugger bmj677 years ago
Simple greed. If they make them with shorter electrodes they use a bit less material (less cost). THen the marketing guys come up with the spin and the accountants mark up the price to match the hype. That said, I don't know if it would work or not, but the cynic in me says this is a case of marketing hype backed by Dollar Lust.
Again, it's more important to see data in a non racing application. Low compression, lower voltage/amperage ignition system, very low comparative engine speed. It doesn't really matter if they make them or not - it would be more compelling if they were OE equipment ;)
bmj67 (author)  trebuchet037 years ago
The only data that I have is that I pickup 1-2 mpg compared to stock and I feel improved acceleration. Do a Google search and see what other people have to say as well I'm not the only one. I'm not going to go out and spend hundreds on dyno testing. The whole point of this is to get better gas mileage and improve performance without spending a ton. Like i said before I replace my plugs often and this is just my experience with side gapping. You can do what you want no one is forcing you to cut your plugs. But I for one will not pay $5-$6 for a spark plug that won't be in my engine over a year anyway. OEM are cheap they just do the bare minimum to maximize profit.
Do a Google search and see what other people have to say as well I'm not the only one.

I have ;) We're also not the only one's that are asking for empirical evidence... The people making claims don't really have empirical evidence :p Unfortunately, most of the anecdotal evidence is base don people that are changing plugs anyway - so any gains are very likely a result of going from an old plug to a fresh one.

The only data that I have is that I pickup 1-2 mpg compared to stock and I feel improved acceleration.

"Feel" is too subjective - the key factor of the psyche wanting a result after invested effort... And 1-2mpg is well within driving style and environmental error (even station pump error :p). Not nearly enough to call it a result. However, a dyno isn't needed ;) You can do A-B-A testing and get a decent result. ABA Testing.

The whole point of this is to get better gas mileage and improve performance without spending a ton
That's completely fine - there's several communities dedicated to just that :p But if you can't prove or repeat a result, you didn't have one ;) All we have to go on at the moment is a manufacturer's claim that you won't have any increase.

I'm not saying it's not worth testing - my point is, if anyone is going to make a claim, they better have objective, empirical (not anecdotal) data and need to explain their methods so others can test and confirm. Frankly, this is cheap enough that I'll probably be testing it - but that likely won't happen until summer :p
bmj67 (author)  trebuchet037 years ago
Most other people are like me and don't want to spend the money to get the empirical evidence. :) I know what you mean about going from old plugs to new. Some people never change spark plugs because they think plugs last forever.

I know feel is different for everyone and that the placebo effect doesn't just apply to just pills.

I'm not saying it's not worth testing - my point is, if anyone is going to make a claim, they better have objective, empirical (not anecdotal) data and need to explain their methods so others can test and confirm. Frankly, this is cheap enough that I'll probably be testing it - but that likely won't happen until summer :p

For the price if it works for you good if not your out maybe $10 and a little bit of time.
This is a very good instructable, and I know for a fact that it increases horsepower about %20 per cylinder due to me testing this a bit in one of my hot rods on the dyno. I would suggest making the gap even just a little bit bigger too.
Pizzapie5004 years ago
Set the gap? What does that mean?
bmj67 (author)  Pizzapie5004 years ago
You need to set the gap between the side and center electrode by first measuring and then bending the side electrode in or out.
Advance the timing and have the thing ping its head off great. Duh
can you please update the video it doesnt work???
OBar6 years ago
I drive a four cylinder Chevy S-10 in desperate need of an oil change. ( I dunno why I felt the need to inform you of that) I used to work for a man who built and drove race cars, and he said that for a daily driver car, regular maintenance and care goes a long way.
joeofloath6 years ago
Does this work for 2 strokes? I have an old quad I'm converting (instructable coming :)) and it might need some more power...
ajilitee6 years ago
What about those fuel additives? I am getting desperate my commute is getting out of hand.
Fuel additives are fine if you want to add something occasionally to clean your engine, but you would be better off using a product like 10K for that. With regards to performance, fuel additives add elements to your fuel which will not burn as well as the petrol. What happens with most fuel additives is that you lose horse power. They are a great scam in that regard.
gin_road6 years ago
Hey, my Kawasaki ZRX-1100 uses this technology. It uses an NGK plug#CR8EK. This plug not only uses the side gap technology, it doubled it!!!, It has two ground electrodes on the plug placed 180 degree's apart. Only one downside, 8 to 10 bucks a piece.
trebuchet037 years ago
From the horses mouth:

There are some exceptions, though. Extremely high compression cars or those running exotic fuels will have different spark plug requirements and hence NGK makes spark plugs that are well-suited for these requirements. They are classified as "specialized spark plugs for racing applications". Some are built with precious metal alloy tips for greater durability and the ability to fire in denser or leaner air/fuel mixtures. However, installing the same spark plugs Kenny Bernstein uses in his 300+ mph Top Fuel car (running Nitromethane at a 2:1 air/fuel ratio and over 20:1 dynamic compression) in your basically stock Honda Civic (running 15:1 a/f ratios with roughly 9.5:1 compression) will do nothing for you! In fact, since
Kenny's plugs are fully 4 heat ranges colder, they'd foul out in your Honda
in just a few minutes.


Some of these "specialized racing plugs" are made with precious metal alloy center/ground electrodes or fine wire tips or retracted-nose insulators. Again, these features do not necessarily mean that the spark plug will allow the engine to make more power, but these features are what allow the spark plug to survive in these tortuous conditions. Most racers know screwing in a new set of spark plugs will not magically "unlock" hidden horsepower.

I'm also more inclined to believe a company that makes an anti-claim over one that makes a claim (Especially without data to back it up):
NGK as a company tries to stay clear of saying that a racing spark plug (or ANY spark plug) will give you large gains in horsepower. While certain
spark plugs are better suited to certain applications (and we're happy to counsel you in the right direction) we try to tell people that are looking to "screw in" some cheap horsepower that, in most cases, spark plugs are
not the answer.
This rings very true, in one of the first hot rods I built in the early '90s being at the time just a teenager. I thought that I had done enough to warrant changing to specialized plugs of this sort. Simply adding a larger carb. and exhaust to an engine will not even bring you into the ball park of needing this type of spark plug. The car I was building at the time never ran 100% untill I replaced the $10.00 spark plugs for some good old champion $.99 units. sure you change them when you change your oil (well almost that often) but who cares. For your daily driver you should be popping the hood every couple of weeks just to check on everything anyway.
bmj67 (author)  trebuchet037 years ago
I never said you had to just use the plug in your car or truck. There are many motorcycles and atvs that have compression rations above 10:1 stock. Also there are cars that come from the factory with turbos and superchargers. They are not your average Honda civic.
That's fine and all - but again, I stand that a claim requires empirical evidence to be believable ;) There are cars that have dynamic compression - these are the minority on the road as with higher compression engines.

Finally, I'll reiterate the NGK statement to the purpose of this modification...
Some are built with precious metal alloy tips for greater durability and the ability to fire in denser or leaner air/fuel mixtures...
(running Nitromethane at a 2:1 air/fuel ratio and over 20:1 dynamic compression)...
these features are what allow the spark plug to survive in these tortuous conditions.
nibbler1256 years ago
ill try this i have a 3 wheeler that likes to miss and load up allot
Tightwad7 years ago
Ok, lots of people seem confused by various Spark Plug terminology. First: Hotter/Colder- The spark is not "hotter" or "colder"...it's a spark. Gap size is set/determined by the ability of the ignition coil to bridge the gap. The stronger the Coil, the wider the gap can be...wider is better because it opens up firing area a bit more. Hotter/Colder actually refers to the plugs ability to bleed of heat. If you look down into the spark plug, you will see that the ceramic inslator portion is different lengths on different plugs. This is what determines the "heat" range. Having a hotter/colder plug is not better/worse...rather you need a plug that will run at the optimal temperature for your application....Motors that run hot using Alcohol or similar need "colder" plugs to help reduce the change of the spark plug turning into a glow plug. Spark Gap/indexing...this mod- This will, for 99.5% of the people out there, have no positive effects in their applications. This doesn't make it bad, or false advertising, simply not beneficial. There are so many other places you lose power and effeciency that making up for it in this one place will not be noticable. This would be the LAST thing you do after you have upgraded/improved everything else along the way. Opening up the ignition area, or indexing your plug relative to the Intake Valves works, but is only quantifiable in high-performance applications where everything else is already optimized. Downsides to this mod - As others have pointed out, you will get more wear from this mod, and thus will need to adjust/change your plugs more often. There are no negative side effects otherwise, simply shorter life span of the plug and gap setting. Regular plugs will NOT work better than plugs correctly modded this way. "But I felt a difference"- Sorry, but there isn't anyone short of a seasoned racer that could feel the difference that JUST this mod makes. You can't feel a 1-2 HP increase(if you even get that) by the seat of your pants....1-2 HP is less than 2% gain. Tightwad ASE Certified spoilsport
Thank you for clearing that up, it's good to hear a voice of reason every once in a while on the internet, even on this site.
Malaachi7 years ago
Won't they foul faster?
If this does in fact burn fuel more efficiently, I don't personally know, than theoretically... yes it should foul quicker. Fouling is a result of carbon deposits left from ignition, however you are also burning more fuel per stroke. Petrol engines are famously inefficient at fuel usage. A very large percentage, I don't have specs sorry : (, of gasoline is pushed out through the exhaust. That's why modern vehicles in the US are required to have Catalytic Converters; their purpose is to burn any unburned fuel and lower Carbon/Nitrogen emissions.
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