Ok, so here we go with the dumb questions. Please bear with me as my backgound is mechanical engineering, not electronics, but I want to understand this stuff.
Good old wikipedia says....
Transient voltage suppression (TVS) diodes
These are avalanche diodes designed specifically to protect other semiconductor devices from high-voltage transients. Their p-n junctions have a much larger cross-sectional area than those of a normal diode, allowing them to conduct large currents to ground without sustaining damage.
Avalanche diodes
Diodes that conduct in the reverse direction when the reverse bias voltage exceeds the breakdown voltage. These are electrically very similar to Zener diodes, and are often mistakenly called Zener diodes, but break down by a different mechanism, the avalanche effect. This occurs when the reverse electric field across the p-n junction causes a wave of ionization, reminiscent of an avalanche, leading to a large current. Avalanche diodes are designed to break down at a well-defined reverse voltage without being destroyed. The difference between the avalanche diode (which has a reverse breakdown above about 6.2 V) and the Zener is that the channel length of the former exceeds the 'mean free path' of the electrons, so there are collisions between them on the way out. The only practical difference is that the two types have temperature coefficients of opposite polarities.
So if I get this, you're effectively allowing the voltage generated by the injector closing to disperse through the diode into the flyback wire, which helps it close as there is no 'resistance' (not in the electrical sense) to it closing, because the specific type of diode can cope with a large current?
But what is the flyback wire? and what does it connect to? just Ground?
