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SPArKy_Dave

More TFI Theory of Operation INFO

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TFI ignition module is what you call "transistor ignition", the actual current being controlled with a transistor instead of mechanical switch.
BESIDES this, it also has a very simple dwell control. Below about 2000 rpm it starts to lower the dwell to prevent the coil overheating and reduce wasting power. Variable dwell is so conservative that you don't need to know about it, but it's neat to know, it won't require any special ignition coil or anything. In addition, there s a feature where if it does not receive a trigger pulse for a second it turns off power. You might have heard about "don't leave the ignition on" if you have petronix or compufire, because these will keep charging the coil until they overheat if you leave key on but engine off, THIS won't.

The module fires "going high", meaning uses a zero-12 volt signal, and fires when it goes to 12v. It will actually work fine as low as 8 volts(maybe lower) and as high as 16; it's not picky.


There are actually Four kinds of TFI module.
Grey(regular) and black(CCD), and distributor mounted or remote mounted, for four combos!
The distributor mounted ones have three pins coming out the side but actually are the same functionally.
Legend has it, in the the CCD ones are supposed to be black but the aftermarket didn't stick to the color codes. I collected three black ones so far and only one is actually CCD unit. THE CCD is computer controlled dwell if you haven't yet guessed.
CCD the coil fires going high, and charges going low, so the trigger signal controls the dwell also. These can be used with points too, but the points will control the dwell..........which is probably not as good, but sometimes good. I used one on a motorcycle. Controlling only one cylinder it made more sense to use the black one IMO.

 

TFI can run any coil. It has "current limiting" at 6-8 amps.
This means once the coil ramps up(charges) to 8 amps then the module holds current at 8 amps by lowering the voltage to the coil as needed.

Our stock ignition usually runs a 3 ohm coil, to limit current to 4 amps.

TFI if you use a 2 ohm or 3 ohm coil it will not be using the current limiting.
I recommend a coil in the 1.5- 2 ohm range for a four cylinder.
The ford coil was 0.7 ohms, and will work too, but it may not be the best, I don't need a coil that charges fast enough to turn 10,000 rpm.

 

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