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| Bosch SU12 Coil https://www.ausmini.com/forums/viewtopic.php?f=2&t=53250 |
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| Author: | miniDave [ Fri May 15, 2009 2:16 pm ] |
| Post subject: | Bosch SU12 Coil |
Thought mine was a GT40R until I dug it out and it turns out to be a standard SU12. Looked back at the discussion about resistors etc and don't know if a need a 'resistor' one or not. It is connected to a standard 25D distributor still running points and converted from dynamo to alternator for power (negative earth) cheers |
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| Author: | drmini in aust [ Fri May 15, 2009 2:45 pm ] |
| Post subject: | |
SU12 is the Bosch replacement for std Mini. It is a 12V coil (3 ohm), not a `use with ballast resistor' one. |
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| Author: | miniDave [ Fri May 15, 2009 2:57 pm ] |
| Post subject: | |
Thanks Doc - so what does (if needed) the resistor do? Is it for electronic ignition, type of wiring harness? |
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| Author: | drmini in aust [ Fri May 15, 2009 3:06 pm ] |
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miniDave wrote: Thanks Doc - so what does (if needed) the resistor do? Is it for electronic ignition, type of wiring harness?
The idea of using a resistor coil is to get more V for cold starting, nothing more. Instead of having a 12V coil with 3 ohm primary resistance you have 1.5 ohm one , and a 1.5 ohm wire wound (onto ceramic) resistor wired in series with it. In normal running, 12V is applied to the end of the resistor so the primary is 1.5 + 1.5 =3 ohms. When COLD cranking (at maybe 7 or 8V) there is another connection made from the starter switch to the coil + terminal, bypassing the resistor. 7V into 1.5 ohms. So you get more output voltage during cranking than you would with the same 7V into 3 ohms. That is how my Valiant and other cars worked it. As for later UK Minis, I'm not sure. |
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