Overview: Spark Plug Technology


In a reciprocating gasoline engine, power is created by a sequence of events as a piston travels up and down inside a cylinder. Near the top of the compression stroke, a mixture of air and fuel is compressed in the engine's combustion space above the piston. Once the piston has reached a specified point during the compression stroke (typically just before TDC piston position), the compressed gases are ignited by a spark from the plug's tip (or electrode). When this combustion occurs, an incredible amount of energy is released in the form of expanding gases. Because it is attached to the engine's crankshaft by way of a connecting rod, this downward movement of the piston creates the rotational energy needed to propel your vehicle.

Better Burn of Air-Fuel Mixture

Air Fuel Mixture

Today, most car, truck and motorcycle engines use a 4-stroke combustion cycle to convert fuel into power. During the fourth cycle of strokes (intake, compression, power and exhaust), no spark occurs. Any unburned gases are delivered to the atmosphere during the exhaust stroke, after which the intake stroke follows to provide a fresh air-fuel charge. Unfortunately, both 2-stroke and 4-stroke engines emit hazardous, unburned fuel residues into our atmosphere. Consequently, the power generated by the engine and the amount of unused fuel exhausted are dependent upon the effectiveness and completeness of the burn.

The Path for Going "Green"

During our engineering research, we discovered that the electrode on a typical J-wire plug utilizes a single sharp edge that often wears much too fast. Our conclusions led to the development of a diamond shaped design with a center electrode tip that exposes multiple edges to an engine's combustion space. Since electrical impulses naturally follow the path of least resistance, this made it easier for our new electrode design to provide a well-formed spark. When tested, this configuration resulted in a better burn of the compressed air-fuel mixture before the beginning of the exhaust cycle. By lowering the emission of unburned gases, we had discovered our path for going green.

Reduction of the Coefficient Variance

Engineering scientists studied the actual pressure rise from a single combustion event with different spark plug designs. The measurement is called the Indicated Mean Effective Pressure (IMEP). This value is determined by running a series of combustion cycles and comparing the values from one spark plug to another, keeping all other parameters (load, rpm, temperature, humidity, and related factors) equal. Double-blind tests were run comparing the area under the pressure curves itself for 500 combustion cycles per spark plug design. Then, we refined our electrode design to reduce the Coefficient of Variance (COV) for a series of combustion cycles. This research work was initially performed at our test labs in Atlanta, and continued with further development and evaluation at Georgia Tech and Michigan State University's Engine Research Laboratory.