Re: sourcing new starter
Posted by HH56 On 2010/5/12 13:51:58
They are a transformer with two windings. However, in most ign coils the windings are tied together at one of the terminals so essentially it becomes a single coil of wire with a connection at one end and another somewhere farther up and then the third for the plug wire.
Here's a simple sketch from an old source showing typical construction. Newer ones are on some of the how it works sites but are not as clear since they are "cut away" views with coils of wire and it's hard to see the routing.
If you change the wires so the polarity is correct as shown, you get the full effect of the entire winding between ground and the HV terminal. If you don't, then essentially the bottom or primary part is out of the circuit as far as the secondary is concerned since ground is now several hundred turns of the way up. The reverse in polarity also makes the spark want to jump from the shell to the center electrode which also reduces efficiency.
Some coils do have individual windings and the secondary is grounded to the case rather than the terminal.
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Here's a simple sketch from an old source showing typical construction. Newer ones are on some of the how it works sites but are not as clear since they are "cut away" views with coils of wire and it's hard to see the routing.
If you change the wires so the polarity is correct as shown, you get the full effect of the entire winding between ground and the HV terminal. If you don't, then essentially the bottom or primary part is out of the circuit as far as the secondary is concerned since ground is now several hundred turns of the way up. The reverse in polarity also makes the spark want to jump from the shell to the center electrode which also reduces efficiency.
Some coils do have individual windings and the secondary is grounded to the case rather than the terminal.
Attach file:
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