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The job of the spark plug is pretty simple: convert electrical energy that has traveled through the spark plug wire into a spark that is directed into the combustion chamber. This spark is relied upon to catalyze the exothermic chemical reaction known as internal combustion that makes power within the motor. (For more details of internal combustion, please see the April 1999 tech article, Making More Power.) Power does not come from the spark itself, but rather from the energy released during the resulting chemical reaction known as combustion. Yet without an effective spark, we have no chemical reaction – and hence no power.
A spark plug creates its spark by forcing the electrical current to jump a gap between the plug’s center electrode and ground electrode – thus creating an arc. But the distance between the electrodes – also known as "the gap" – is very important. If the size of this gap is too little, then the resulting spark may be too small and may not reach far enough into the fuel and air mixture to ignite the mixture. However, if the size of the gap is too large, then there may not be enough energy within the electrical current to push across the gap and create an arc. An ideal gap, therefore, is a distance between the electrodes that extends sufficiently into the fuel and air mixture while not diluting the strength of the spark. In most cases, we recommend adhering to the factory-specified gap – which is .040 inches in the 1.9L of the ‘S’ car (both SOHC and DOHC) and the 3.0L of the ‘L’ car and .045 inches in the 2.2L of the ‘L’ car. (Please note that 1996 models were introduced with a .060 inch gap, but this was later revised to .040 inch through a technical service bulletin.) However, we have used gaps on 91-98 DOHC models as large .060 inch in combination with Nology wires and Silverstone spark plugs with excellent results. To gap a spark plug, you need a "spark plug gapping tool" which will measure the distance of the gap and, in most cases, provide a prying tool for moving the ground electrode away from the center electrode. When gapping spark plugs, you must use extra caution to protect the center electrode. Any force that moves or distorts the center electrode will negatively affect the performance of the spark plug. |
