6V Silver Permatune tested

[Fred Winterburn]

Folks,
One of the members here sent me a working 6V Permatune CDI for testing. This is a natural aluminum model built in Wylie Texas, so it is at least as new as 1993. I did not torture test this unit. I ran it to a maximum of 8 volts and minded the polarities very carefully! By the extra weight I knew it was potted and therefore, un-repairable. This is what I found:
-Voltage not excessive, but also not controlled. (reduced voltage reduces insulation stress, so a good thing)
-Spark duration: 50µS (quite short, and undesirable)
-Single phase, negative polarity spark. (similar to MSD except not multi-spark) Older blue permatunes had a positive going spark followed by a negative spark in the same spark event (if I recall correctly).
-Spark energy weak, but does not vary with rpm. Stays the same as rpm increases.(similar to MSD and a desirable feature except for being weak).
-Spark voltage and energy vary directly with battery voltage. IE, the lower the battery voltage, the lower the spark energy and voltage. (similar to MSD and very undesirable)
-Unable to produce a useable spark below 5.5V battery voltage. (very undesirable on a 6V car)
-3 amp draw at 267 sparks/second, 8000rpm on a 4 cylinder or 4000rpm on an 8 cylinder. (Not bad except the spark is extremely low energy, so the power supply is inefficient). The directions for the 6V model state that it can 8 amps continuous, and recommends a 30 amp fuse! There's no way the unit could possibly draw 8 amps with 7.5 volts applied. Perhaps the 12V version of the silver permatune does draw that much at the maximum spark rate, but not the 6V model.
-Maximum spark rate without misfires is 267 sparks/second. The trigger circuit will not switch properly above that spark rate and misfires occur.
-Trigger resistor is 100 ohms. This would not work on most 6V cars without the points crudding up for lack of wetting current through them. VW and Porsche seem to be somewhat immune and can get away with less current. One person suggested to me recently that the Bosch points slide a little as they make and break contact that helps over other point designs, but I can't see that on the similar Bosch points in my Volvo dizzy. I use 18 ohms in my 6V units for example.

I do not think there is a fault in the unit that was sent to me for a test. The nature of the test was to check out the performance of a known, good, 6V Permatune. Personally, I am less than impressed with this unit. It ties in poor performance to a mid eighties Tiger CDI I bought when the Tiger brand was being manufactured by Universal Corp. (Tri-Star became Universal, and Tri-Star was owned by Delta originally) The Tiger CDI was a rip-off of the Hyland design but poorly executed. The first series of Tigers made by Delta in the late sixties were the best, but still flawed. Considering the Permatune was built relatively recently, I expected much better performance. I would not use it on any car of mine, despite it being a CDI with some of the benefits that gives.
The 12V blue Permatune I have from circa 1974 (made by Aero Design Products Corp), also has a weak spark, but not as weak, with a useful rpm for a 6 cylinder, but not a bad design overall. It adheres very closely to the design of Theodor Sturm who filed for his patent just a few days after my father filed for his in 1963. The two designs are considerably different, with my father's being simpler and arguably more effective. Of course, I'm biased! Fred

[Mervyn Hyde]

Like your work Fred! I have used the MSD setup on my early 911 for some years and really wouldn't be without it.

I would be interested in your take on the Gammatronix if that crosses your path at some time.

[Fred Winterburn]

I had a quick look at the Gammatronix website. Looks like a simple inductive switcher. Unless it has some form of dwell control, it can't possibly give a higher energy spark than points/condenser using the same coil, despite the advertising. Fred

Like your work Fred! I have used the MSD setup on my early 911 for some years and really wouldn't be without it.

I would be interested in your take on the Gammatronix if that crosses your path at some time.

[Mervyn Hyde]

Thanks Fred. Yes it seems to run fine with the same advance and other settings. It just takes the pesky condenser out of the equation.

[Fred Winterburn]

I've added a couple of articles I wrote concerning Pertronix 1, which is a basic inductive switcher without dwell control, and another article on the function of the condenser in the Kettering system. The gammatronix and pertronix for that matter both claim higher voltages than the Kettering system. That's true because the voltage is not limited by the condenser. It has to be limited by a zener diode (usually) instead. Also, if the same coil is used, the voltage overshoot before the spark breaks down is greater with the inductive switchers because of the inherent voltage drop on the semiconductors used to do the switching. Weaker inductive ignitions have a higher voltage overshoot than high energy inductive ignitions. Between the 3 articles it should all make sense. Fred

I had a quick look at the Gammatronix website. Looks like a simple inductive switcher. Unless it has some form of dwell control, it can't possibly give a higher energy spark than points/condenser using the same coil, despite the advertising. Fred

Like your work Fred! I have used the MSD setup on my early 911 for some years and really wouldn't be without it.

I would be interested in your take on the Gammatronix if that crosses your path at some time.

[Mervyn Hyde]

Will read with interest Fred. I had tried the HotSpark (roughly the same as Petronix in operation) earlier, but found it would not work at all with my 6v system. It needed major alterations in the advance/retard timing and then still wouldn't operate properly.