wasn't there a topic on this LONG ago on here? I have a spare duraspark dizzy and harness and a spark remote mount TFI setup and was gonna try and marry the two together.
any help out there?
any help out there?
TFI module running off duraspark dizzy?
- Thread starter XFlow_Fairlane
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in2hotrods
Well-known member
Seems like he says that you can't. I'd be interested in what the article from the 2nd post has to say.
According to the guy at www.gofastforless.com both the Duraspark and the GM HEI distributors use an analog type signal whereas the TFI uses a digital signal. Therefore it is possible to trigger a GM HEI module with a Duraspark distributor, which I am currently running. You can also trigger a TFI module with a breaker point distributor, which I have also done on a friend's pickup.
Dunno about triggering a TFI module with a Duraspark though, but gofastforless says no.
Joe
Dunno about triggering a TFI module with a Duraspark though, but gofastforless says no.
Joe
the DirtySpark dizzy houses a VRS (Variable Reluctance Sensor), which generates an analog AC signal (think sine wave, or fluid up-down motion). The DuraSpark and HEI modules trigger on the rising side of the wave. A TFI dizzy houses a Hall Effect type sensor, which is more like a magnetically actuated on-off switch, and generates a digital DC signal (think a line of blocks evenly spaced apart). The TFI module triggers when it sees the signal drop from a positive voltage (usually 5v) to zero. This explains why points will function with a TFI module, but not the DuraSpark dizzy.
fb71":1yg40nb6 said:
Thank you, it's been nearly 30 years since I had access to an O-scope so have no way to verify and I have to trust others. I am confident that your assessment is correct because the modifications have worked as advertised. The TFI module/coil on a breaker point distributor is a really slick way to upgrade an older engine to hotter ignition with junkyard parts.
Joe
well I guess thats one little wiring project off my board then.
Well, I haven't directly put a scope on the duraspark output, but a GM module WILL trigger off a strait square wave.
Or just about any oscillating wave for that matter.
Now, if the TFI stuff demands a square wave as opposed to a sin wave, you can use a few diodes to turn the sin wave into a square wave, of sorts.
Or you could replace the pickup and reluctor wheel in the duraspark with one from a TFI.
Or just about any oscillating wave for that matter.
Now, if the TFI stuff demands a square wave as opposed to a sin wave, you can use a few diodes to turn the sin wave into a square wave, of sorts.
Or you could replace the pickup and reluctor wheel in the duraspark with one from a TFI.
Bort62":361mapjg said:
I might have to open one of the spare durasparks up and look into this. the TFI pickup mounts around the shaft on a 3/4" or so bushing and has a pin for a vac advance on it (ford used a rod of different lengths to set base timing on the bench) so maybe with a bushing it can be made to work fairly easy in a DS2 setup once to swap the shafts on them.
FLSHBCK":35434d4z said:
The HEI module is less selective about the shape of the input signal. As long as it sees a rise from 0 to positive V, it should respond, but I don't know for certain, never tried it.
I doubt you'll need any type of inverter, just rotate the dizzy the few extra degrees required for the spark event to occur on the signal fall. However, that may put the rotor too close to the next terminal in the cap.... hmmm.... may have to look at this more closely....
I use GM HEI Modules at work to trigger all sorts of stuff, and I drive them with a strait 12v ac square wave.
You can also drive them with a sawtooth wave, a sin wave, or just about anything that oscillates around 3.5v or higher in amplitude.
It switches on the rise at around 3.5v IIRC. Just make sure the bottom portion of your wave is well below 3.5V or else the module will stay on and get REALLY hot. One of our engineers burnt his hand really bad on one.
The GM Module is really a great package, it takes a differential logical input and can drive all sorts of high current devices on the output, performing all the nice isolation and switching you would want in a small inexpensive package.
I have replaced transistors with them in applications that were very noisy and high current/high voltage.
You can also drive them with a sawtooth wave, a sin wave, or just about anything that oscillates around 3.5v or higher in amplitude.
It switches on the rise at around 3.5v IIRC. Just make sure the bottom portion of your wave is well below 3.5V or else the module will stay on and get REALLY hot. One of our engineers burnt his hand really bad on one.
The GM Module is really a great package, it takes a differential logical input and can drive all sorts of high current devices on the output, performing all the nice isolation and switching you would want in a small inexpensive package.
I have replaced transistors with them in applications that were very noisy and high current/high voltage.
Well I run them at about 6 amps 50% duty cycle for short periods without any problems. 24v DC.
The current limit and duty cycle is going to depend pretty heavily on being able to heat sink it properly.
In terms of making the DSII output into a square wave for TFI, by using a zener diode that is slightly lower than your peak voltage, you can flatten the top of the sine wave. If I thought about it enough I think I could figure out a clever way to chop off the rising/falling portion of the wave as well, so you would end up with square - looking wave. depending on how you setup the diodes you may end up with something less than 50% duty cycle, but that shouldnt matter for this application.
The current limit and duty cycle is going to depend pretty heavily on being able to heat sink it properly.
In terms of making the DSII output into a square wave for TFI, by using a zener diode that is slightly lower than your peak voltage, you can flatten the top of the sine wave. If I thought about it enough I think I could figure out a clever way to chop off the rising/falling portion of the wave as well, so you would end up with square - looking wave. depending on how you setup the diodes you may end up with something less than 50% duty cycle, but that shouldnt matter for this application.
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