Save Gas and Incerase Horsepower by Side Gapping Spark Plugs





Introduction: 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

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.

Step 2: Removing Burrs

Next you will need to use a file to remove any burrs left from cutting the ground electrode. If this step is not done the burrs could heat up until they glow red hot causing detonation. After the burrs are removed you will want to use some alcohol or starting fluid to thoroughly clean the plug to make sure there are no metal filings left.

Step 3: Setting the Gap

After all the burrs are removed you must set the gap. To do this you will need to find the manufactures setting for your vehicle and reduce that by 0.010". Example: manufacture setting 0.035" - 0.010" = 0.025". Then using a feeler gauge of the correct thickness insert it at a 45* angle to check and adjust as necessary until the gap is correctly set.

Step 4: Before & After

Here are before and after photos of a non side gapped vs. sided gapped spark plug. With the side gapped plug the spark is now un-shrouded and is more exposed to the fuel/air mix. the flame created will now be able to spread faster resulting in a more efficient burn before the exhaust valve opens.



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Use caution increasing spark plug gaps. I did this on a Ford Ranger 3.0. It seemed to run OK but within a month the coil went bad and had to be replaced. It appears the coil has to work harder as the gap increases. I changed the gap back to factory specs.

The sparks are the same size in any plug configuration (side gap or regular) as the spark can physically only go from the center electrode to the ground electrode (hook portion) and does not throw past it.

Cutting the ground electrode gives you a smaller area for the spark to jump to eliminating reliability. The spark can only go from corner to corner, rather than having the ability to use the entire flat surfaces on both sides to find the best path when carbon deposits build up and hinder spark.

Check out the plugs on this page for an extreme version of this plug mod.

Taken from the link below: "A racing plug differs from a street plug typically by the heat range and expectation of durability. Also the long-life electrodes in the street plugs is designed for longevity. "


I think you may have misread the article you cited. "Spark plugs with fine wire center and/or ground electrodes operate better for two reasons. First, a smaller center electrode requires less voltage to jump the gap. This means fewer misfires, which will be seen in higher mileage and more horsepower. The second reason is smaller center and ground electrodes reduce quenching." This means that the smaller area you mentioned actually makes for a better spark.

I had a bid problem with my turboed 98 Yam R1 could just not get it to cold start had to send propane gas into the turbo and even so...So finally I found the solution, took out the resistances from the sparkplug caps (20 Kohms...!!)

and changed the CR9E plugs for nonresistor C9E spark plugs (5 Kohms) and now it runs great you can fell the bike has more power and starts up under all conditions. Absolutely no Rf inteference that all a joke to reduce emissions. Because to reduce pollutant emissions you have to have a not too good combustion like Guy Martin (TT champion and mechanic) explained in one of his videos

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.

Just increasing the gap will not make the spark better; it will actually weaken it. The air-fuel mixture has a much higher resistance than the metal of the electrodes so making the gap larger makes the resistance that much more. You would have to increase the power to the plug in order for the spark to be able to cross the increased gap. To learn more, please google basic electrical theory and how spark plugs work.

Can this be applied in a motorcycle sir ?

Lastly, I googled "Top Fuel spark plug size comparison" and could not really find any major differences compared to your standard engine. The top fuel dragsters have much larger cylinders and 8000 hp (1000hp per cylinder) yet the spark plugs are not that different but use 2 plugs per cylinder and every other component is bigger and better, like the ignition/spark size. Their fuel economy can be 40 gallon per mile!

Look closely at the plug electrodes in the cylinder head picture I included. How big is your ignition/spark compared to the included photo.


Responding to a comment: what might acetone do to your fuel lines and plastic parts in your engine? What is acetone usually used for, nail polish remover, etc? What if acetone eats your fuel line and sends the bits of rubber or plastic into your engine and burns/cakes onto the plug? I don't know, maybe it will clean your engine and plug but may harm your oxygen sensor or catalytic converter or clean the oil off your cylinder walls removing the lubrication and causing more wear. Some octane boosters say they can harm engines and other parts but give more power.

Every car manufacturer uses different spark gaps and levels of spark energy. A Top Fuel racer is using a MUCH more powerful spark, completely different fuel and may use 11.2 gallons per second which is the same as a 747 plane.

Don't you think an engineer might know a bit more than the average home "bench racer"?

Speaking of different fuels racers use and additives like the guy who mentioned acetone, the cost of fuel is directly related to your MPG cost everyone is talking about. Acetone is much more expensive than gasoline and may be much more harmful to your car and pollution. Our gas prices are cheap compared to other fuels, you pay more for Hersheys syrup & laundry detergent than gas.

The Ethanol they put in our fuels is more harmful to our cars, especially older ones which were never meant to run it, which is why Ethanol is limited to 10-15%, and why there are Flex Fuel E85 (85% gas/15%Ethanol) designed vehicles. Ethanol pollutes less but also makes less power. There is more concern for pollution than your power output and life of your engine.

Are you really so desperate for 1% increase in horsepower (maybe with a plug) in your car which you can't detect anyway unless on a drag strip and at full throttle and worse MPG? Your HP is measured at full throttle, worst MPG and "perfect" conditions, new and at sea level. Calculate 0.01 of your power and MPG. If you have 200hp x 0.01 = 2hp max under perfect conditions! An air intake and exhaust upgrade is a more realistic upgrade with much higher gains.

read these articles to understand more.