Only when one really looks at the anatomy and working behind the spark plug wires, he can get a clearer picture about the spark plug wires. A spark is created only when the insulator within it breaks down and the electrons within it get swiftly discharged across it.
The generation of spark can be broken up into a series of four different phases.
The first phase starts with an abrupt fall in resistance and this takes forward to the next step. The next phase starts with a flow of current runaway whereby an indicator runs that if more current flows, it results in lower resistance, and concurrently increases the current flow subsequently.
The 3rd phase starts when there is a collapse of the voltage when the second phase low resistance pathway releases the pent up energy. Then fourth and the last phase is marked by the soaring current flow at the low voltage passing through the insulation.
If we try to plot the voltage against the time for a typical spark that releases from the automotive ignition coil, we shall find that the voltage initially rises rapidly until the occurrence of the breakdown in the mixture. It then starts collapsing with the fall of the voltage & it stabilizes at a very high current where the voltage becomes constant. Spark duration was seen to run for about approximately 1.5 mS.
When we talk of the first breakdown, it is important to know why it is caused. The reason behind such breakdown is high density of the electric field. This electric field has a one to one relation with the voltage and hence high voltage corresponds to a stronger electric field.
Electric fields are characterized by automatic hastening of any charged particles in their field like ions and electrons. These accelerated particles come in contact with the atoms in the vicinity and release electron from them which again get the acceleration provided by the electric field. A good strength of the field leads to a cascading effect in the reaction mentioned till a point when a significant quantity of atoms within the insulator get ionized and cause conduction and breakdown.
For any voltage whatsoever, the density of the field is always inversely proportional to the surface radius. Thus the arcs are generally seen to start at sharp edges and corners where density is the highest.
One should also know that greater pressure in cylinders of the fuel related to the amount of fuel present in it. Greater fuel content in turn needs greater voltage in order to initiate a spark when we talk of the ignition mixture in a motor.
On initiation of arcs, any air flow will necessarily take ionized gas away and thus blow out the arcs. Breakage of such arcs raises the voltage which leads to further arc formation. High airflow, however, can potentially blow out the spark with the amount of ionized gas it can take at a speed greater the the reformation speed of the arcs.
Now that we are clear on the anatomy and working part behind the spark plug, we definitely have more knowledge to understand the various requirements and specifications of the spark plug that is typical to various cars.
