Side Gapping Spark Plugs
DETAILS: 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. SOLUTION: 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 gage 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 and… Have fun!
PHOTO:The left 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. The right 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 gage, set the gap at the narrowest point between the center electrode and the electrode arm. Reduce the gap by .010" than norm specifications.
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.
HOW SIDE GAPPING 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.
First, I cannot take credit for the above writing and pictures. The original article can be found by visiting:
http://performanceunlimited.com/documents/plugsidegapping.html
The above picture is of a group of side gapped spark plugs. Want to guess what they are used in? The Fram Top Fuel Dragster. As you can see everyone of them is side gapped. I took this picture in 2007 at the Topeka, KS Nationals.
I ran across the above article more than five years ago. I have long held the belief that the ignition system on cars is one of the most overlooked areas when it comes to fuel economy and performance. Are you going to pick up gobs of power gains from ignition modifications? Probably not. You can pick up a few horsepower, but in the grand scheme of things it may not be noticeable. You can get improved throttle response and you most definitely can get better fuel economy. One thing I have never been afraid of experimenting with or spending money on is the ignition system. As a result, I have tried just about every spark plug out there as well as every spark plug wire. Rapid Fires, Splitfires, E3's, etc. I have tried them all. Still, to this day, side gapped spark plugs have provided the best results. There are two very important things you have to consider with regards to ignition systems. 1. 2.
The amount of power delivered by the ignition system The resistance to that power
In a typical ignition system there are two sources of resistance after the energy source of the ignition system (Coils, distributor, etc.). The first is the spark plug wires themselves. Typical distributorless ignition systems put out about 35 – 60,000 volts of electricity. That voltage is immediately met with resistance of the spark plug wires. The amperage is fairly low but still enough to do harm or make you remember every being in contact with it. OEM spark plug wires can have a resistance on the order of several thousand ohms (the measure of resistance) per foot. Depending on brand and construction the resistance of a typical graphite core spark plug wire can run from 3 – 7000 ohms per foot. Now if you think about that in relation to the 3800 engine you will quickly realize that there is a great deal of resistance in the ignition system. Even cylinder #1, the shortest plug wire has a resistance about 3 – 6000 ohms. This is why newer ignition systems use what is called a coil on plug set up. Basically, the ignition coil sits on top of the plug boot, minimizing the loss through resistance of any spark plug wires. Most think, okay, I'll get a set of aftermarket wires and cut that resistance right out. Well, unless they give you the resistance per foot on the box, be warned. Most aftermarket wires have a resistance around 4 – 500 ohms per foot. A significant reduction but not quite the lowest. The lowest I have ever seen is around 25 ohms per foot. The popular MSD ignition wires, well they have around 50 ohms per foot. What does this mean to you. Well lets do some math and find out. For the sake of simple math, I'm going to use the following information: -Ignition system voltage = 35,000 volts (I believe the 3800 ignition system is approximately 38,000 volts). -The average spark plug wire length is 3 feet. -Lets use 1 amp as the amperage the ignition system puts out -The average graphite core spark plug wire has a resistance of 4500 ohms per foot. Our formula to determine the voltage losses in an average spark plug wire will be: Amperage X (Wire length X Resistance Per Foot) – This will tell us how much voltage is being lost Then Total loss / Total ignition Voltage X 100% - This will tell us the percentage of loss
1 amp x (3 feet x 150 Ohms/foot) = 450 voltage loss (450/55,000) X 100% = 0.8% First: OEM factory plug wires (Graphite core, average 4500 ohms per foot) 1 Amp X (3 Ft X 4500 Ohms/Foot) = 13,500 13,500/35,000 X 100% = 38.57% Second: Typical Aftermarket plug wires (Spiral core, Average 500 ohms per foot) 1 Amp X (3 Ft X 500 Ohms/Foot) = 1,500 1,500/35,000 X 100% = 4.29% Third: MSD Plug Wires (Measured at 50 Ohms per foot) 1 Amp X (3 Ft X 50 Ohms/Foot) = 150 150/35,000 X 100% = 0.429%
As you can see, the losses can be substantial. In the example of the OEM ignition wires you are loosing nearly 39%. That means that 39% of the voltage that the ignition coils put out never makes it to the spark plug. The lower the voltage to the spark plug, the smaller the gap you have to use. The smaller the gap you have to use, the lower the flame front propagation is and thus a less complete burn which costs you power and fuel economy. There is yet another source of resistance we have not yet considered. The resistance of the spark plugs themselves. Have you ever heard the term resistance spark plug. There is a finite amount of resistance built into the spark plug, though no where near the amount found in the plug wires. However, the very construction of the plugs, the materials they are made of, can be a huge hindrance to the spark voltage. Today you can buy plugs made of all sorts of things. Copper, Platinum, Iridium and so on. The exotic metal spark plugs have become all the rage in recent years primarily because of reduced maintenance. Platinum and Iridium do resist erosion or wear quite well. But the combustion chamber of a normal engine is quite the violent place and presents an extremely harsh environment to spark plugs. I have pulled platinum plugs (the so called 100,000 mile plugs) out of customer vehicles before as a result of a complaint of a lack of power and hesitation with 70,000 miles and found the gaps on the plugs were nearly two and a half times the recommended gap. If you look at the resistances of various metals you will quickly see just what a hindrance some exotic metal plugs are. Lets take a look at a few. Aluminum Gold Copper Silver Platinum Iridium
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2.65 Micro Ohms per centimeter 2.24 Micro Ohms per centimeter 1.67 Micro Ohms per centimeter 1.58 Micro Ohms per centimeter 10.5 Micro Ohms per centimeter! 4.7 Micro Ohms per centimeter!
As you can see, platinum has over 6 times the resistance that copper does, Iridium is nearly 3 times higher. Only Silver comes in with a lower resistance than does copper. In the effort to maximize ignition system efficiency, copper rules. Couple the lower overall resistance of copper plug and low resistance plug wires with side gapping, you will make the most of your ignition systems capability. Now some are put off by the fact that copper plugs wear faster than do the platinum and iridium varieties. While it is true that copper plugs will need more frequent changing than platinum or iridium plugs, there is a way to extend the life of copper plugs. Its a technology that has been around for a while and is used quite a bit in racing circles. Its called cryo treating. Essentially, your parts, in this case spark plugs, are frozen. They are taken down to a temperature of around minus 320 degrees for a specified amount of time and then returned to room temperature using a computer controlled process. Cryo treatment is a tempering process that improves the efficiency of spark plugs on average 12 – 15%. It also significantly reduces abrasion wear which, with regards to spark plugs, means much longer life. The cost of the process varies depending on who does the work, but runs about $10 on average. With the cost of copper plugs, you could still come out cheaper than just buying a set of exotic metal plugs alone and have a plug that conducts far better and lasts nearly as long.
