Pertronics

Your shop is right, you need a tach adapter to connect your (12V triggered) tacho to the coil in a Pertronix setup. Don't wire the tach directly to the coil, this can damage your tach due to the higher voltage.
If you use the Pertronix Ignitor as a trigger unit for your Dinoplex, you could wire the tach directly to the points input, together with the black wire coming from the Pertronix Ignitor.

 

I have used it in other cars and it has worked great. Pertronix has a new model out ver. III that incorporates the box right into a single part that fits into your stock distributer. I have used it and it works perfectly. Not sure if they have one that fits your distributer, you will have to check the application list.

 

Would be interesting if the Pertronix II or III ignitor is available for the S125AX/BX (3 cams) or C (six cams). The Pertronix Ignitor I has a tendency to burn out its power transistor when the contacts are closed and the ignition is left on for some time, which is not a good hardware design. So if you have an Ignitor I installed, keep in mind to switch off the ignition when the engine is not running. (This is not an issue when using the Ignitor I to trigger an external unit as the Dinoplex or MSD as there is nearly no current flowing through the Ignitor in such setups.)

Pertronix fixed that in the II and III series, those also do dwell control. IMHO, this limitation is marketing related, most if not all electronic transistor retrofits nowadays have current current and dwell adaption.

 

Got a Pertronix Ignitor I sold last year for reverse assembly and took a closer look at the potted circuit. The unit uses a V5036 IGBT (integrated transistor circuit) for switching the coil current, so the issue with defects by overheating when the contacts are closed should be nothing to worry about anymore. It seems that Pertronix has used a different IGBT with older units which were prone to burn out when overheating.

The V5036 IGBT is temperature protected, e.g. to protect itself it will lower the maximum coil current when the temperature rises.

Unfortunately the IGBT's heat sink is also used for mounting the unit on the distributor body, so overheating of the Ignitor I in the compact Dino engine compartment is quite likely (happened to me twice on a spirited drive when testing the Ignitor I some time ago).

If this happens, the supplied coil current will drop until the ignition/engine cuts out, in such a case you will notice that the engine will feel quite mushy and won't rev over 3000-5000K (depending on the temperature), and the engine starts to run quite rough. After the engine compartment has cooled down, the ignition will be back to normal. IMHO, not an ideal design for the conversion of a Dino ignition.

 

On the FIAT Dino's it depends on what tachometer you have, the early cars wont work with the pertronix unless you buy that adapter, the later cars will work without the adapter. Since the FIAT production was stopped before the Ferrari version I would assume that those tachs would work. Yet the consensus here it won't.

 

Mike, i think its the other way round. Early Fiat Dino coupes/spiders which came with a points based ignition won't require a tach adapter, their tach should run fine with an Ignitor setup.

Later Fiat Dinos which came with a Dinoplex and all Ferrari Dinos have an electronic Veglia tach and require a tach adapter when using an Ignitor setup to convert the coil's 100-200V kickback pulse on the negative terminal to a +12V square wave signal required by the tach.
On the Fiat Dino such a tach can be identified by the word "Elettronico" above the Fiat label.

 

Hi, I'm resurrecting this old thread since it seemed most relevant to a question I have.
I've installed a Pertronix igniter II ignition system in a couple of Dinos and in my E-series I'm using it to directly drive the coil instead of using the Dinoplex. I have a tach adapter to run with electronic ignition systems and I'm using an otherwise stock setup, plugs, distributor and NGK spark plugs etc.

I've played around with the coil setup and have observed the following:
1) Directly connecting the recommended Flame-thrower II coil (0.6 ohm) causes alot of interference and the engine doesn't run well, the tachometer floats and the engine doesn't rev - I tried additional grounding and checked it with a scope and found there's alot of noise in the wiring so suspected the higher power coil and longer unshielded wires cause poor coil control. It might work ok if I re-routed the wiring and added shielding but I wasn't up for trying that.
2) Connecting to a stock Marelli coil with an external resistor - the car + tach have been running great. The additional resistance is likely reducing the spark intensity, RF interference and crosstalk (bottom of pic below). I didn't try adding an external resistor to the flame thrower II coil but that might work too.

The installation instructions from Pertronix state that you can run optionally with an external resistor but it's installed on the +ve side of the coil (top diagram) whereas the stock Dinoplex setup has it on the -ve side of the coil (bottom diagram, what I use).
The only difference I can think of is that the Pertronix recommended setup may give a more intense spark since the coil -ve terminal may see a faster voltage ramp - but I didn't try it. Does anyone have any experience or insight?
thanks, Andrew
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Glad to see an old post revived periodically. For those here out of the loop, Mike drove John Corbani for John's last ride in John's Dino before John's death, and he was a great help to John's family

 

Hi Andrew,

I have no experience with the Pertronix module, but on the question of where to put the resistor, I am certain it will make absolutely no difference. Only the current is deciding the strength of the magnetic field in the primary winding. And the current is limited by the resistor. Does not matter on which side you have the resistor.
There is another (minor) reason to have the resistor on the plus 12V side, though: When the Pertronix module turns off the current, you will get a nasty inductive kickback on the minus terminal. They have presumably designed the circuit to kill that voltage spike as safely and quickly as possible. When you put your resistor in the minus lead, you add resistance in that loop. It may make that process just a bit less effective (=slower). It may let more transients through to the sensitive tachometer circuit. May or may not be important, but it speaks in favor of the Pertronix recommended connection.

The problem you expired with the Flame Thrower coil is unfortunate, but does not sound all that surprising. 0.6 ohms is a brutal load on the system, very close to a dead short across the 12V supply. Could affect all kinds of circuits on the same supply.
It sounds like you are on the right track with a resistor and a Marelli coil. That is much closer to what the system was designed for.

Best,
Lars

 

Hi Lars, Good to hear from you!
Thanks for the reply and I agree with what you said above, just to point out that the igniter II has dwell control built in (change from earlier versions) so it's not powering the coil longer than necessary but yes it's a pretty high current and spark voltage. I have both coils side by side in the trunk, as they were originally with one for emergency use so they are easily swapped around. I'll get another resistor to run with the flamethrower coil and I'll wire it as Pertronix spec's with the resistor on the battery side to see if a couple of ohms in the circuit helps and calms down the EMI. I'd like to make both coils useable.

Best Regards, Andrew

 

Hi Andrew,
Agreed, you should be able to use both coils. One idea to solve the problem with the high current coil: Temporarily install an extra battery in the trunk, connect the plus terminal only to the high current coil with fairly short and heavy leads. That way you should even be able to use even the 0.6 ohm coil without a resistor. If that setup works, you have found the cause of the problems, and can then work on improving the 12V supply to the ignition. The existing 12V feed to the ignition is not very stiff - to put it very politely. It runs a very long way with a fairly thin wire from the regulator, ignition switch and fuse block all the way to the rear of the trunk. Just a thought.

Best,
Lars

 

OMGjon uses Pertronix