Pertronix (all points replacements) vs Points

[tzepesh]

Thank you very much! So high impedance coil.
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'74 1303S, L98B Viperngrun (extra glitter), German Look
'64 1200, Sea Blue, under restoration

[SGKent]

I am an old guy and remember when electronic ignitions first began to make their way to the consumer. The CDI boxes and combo CDI and coil like Judson, were first. I remember adding a Judson unit to my dad's '68 Roadrunner, and a good friend had CDI built from a kit in his 1965 Mustang. They still used the car points but carried little current, which triggered the CDI. The most common complaint was that over time oil and grease built up on the points, so after a while the points still needed adjustment, cleaning or replacement. But instead of this occurring every 12,000 miles, it was at 60,000 - 70,000 miles. Then came optical and magnetic timing systems sort of like the Pertronix. All sorts of automotive manufacturers got on the band wagon in the 1980's and 1990's. Problem was that many of those systems were easily killed by electrical surges, vibration and other things the harsh use in autos and boats brought to them. Between 1980 and 2000 I replaced a plethora of different units on cars and boats that had failed. Some were for me and many were for friends. As time passed, the units got more reliable and are usually good for the life of the car or boat now. The aftermarket units still do not seem to have the longevity of modern cars. I would think that would have been worked out by now, but modern cars have electrical systems with many computers, and they are designed to be more robust and forgiving than earlier cars like our buses. Modern cars have more protection circuits in them. One need only look at the difference in fuse boxes to know how many fuses there are in a modern car. My MDX has three fuse / relay boxes that I know of, and maybe 30 - 40 fuses total. My VW has what 10 - 12 fuses?

While people are happy to get rid of the maintenance of points, they take a risk to do so. Yes, rubbing blocks can break too but all in all, the performance of a points distributor like Bill or Glenn rebuild is as good or better than an electronic ignition in my opinion. One thing that electronic ignitions are good at, is igniting lean mixtures by allowing a wider plug gap. This allows the higher voltage a lean mixture requires. Seriously, I can't imagine anyone with an air cooled engine that really wants to run it a lot leaner. Yes, if the amount of fuel is reduced to where it barely burns, it will run cool but the resulting flat spots will be awful. Modern engine run a plethora of sensors that help that extremely lean engine monitor its performance to get rid of the flat spots. One just cannot get that using bolt on electronic ignitions.

For the record I wrote this in response to VW owners who are considering using an electronic ignition. CDI units aren't that commonly sold new anymore but I would be more prone to one of those than a fully electronic module type unit. In fact, many early CDI boxes had a simple switch that could be put back to normal points if the CDI failed. Modern units like Pertronix do not have that ability. The problem with older CDI units is that the components inside will have aged, capacitors dried up, and an old one would not be reliable either unless someone went thru it and checked all the components, or even upgraded it.

The exception to this might be the 1979 and later California systems that used an electronic ignition along with an fuel injection ECU and O2 Sensor designed to monitor mixture. The 1975 to 1979 Federal L-jet systems rely on a wave form from a set of points and standard coil collapsing to trigger the ECU to shape a square wave to send to L-Jet injectors to turn them on and off.

All that said, I do know that Pertronix does rely on having the correct resistance coil for the module so always be sure to match the proper Pertronix coil to the module. If I was going to run a Pertronix unit, I would probably want to see some form of a robust isolation voltage regulation and filtering circuit added between it and the car voltage to minimize the risk of a voltage spike or too much ripple in an alternator failure taking it out.
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"Most people don't know what they're doing, and a lot of them are really good at it." - George Carlin

[ashman40]

[oprn]

Nice informative post SGKent! I do however disagree with this statement.

[mikedjames]

I was gald I had an EDIS system the other day, one of the wires to the ECU disconnected so the EDIS-4 modulen just sat there running at 10 degrees advance. At the time I had gone into Winchester which had one medieval bridge over the river on my route and emergency roadworks blocking access. So I ended up in gridlock and then out on narrow country lanes, unaware it was broken. It was only whenI got home I noticed the timing advance dial on the dash display was stuck..


Being more used to modern electronic modules, I assumed it was electronics so I swapped out all the electronics then found a bad wire.

Anyway here is a picture of a random electronic module that melted itself. The engine was still running, just not very well. The owner had driven some distance to the Techenders technical camp-out here in the UK.

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Ancient vehicles and vessels

1974 VW T2 : Devon Eurovette camper with 1641 DP T1 engine, Progressive carb, full flow oil cooler, EDIS crank timed ignition.
Engine 1: 40k miles (rocker shaft clip fell off), Engine 2: 30k miles (rebuild, dropped valve). Engine 3: a JK Preservation Parts "new" engine, aluminium case: 26k miles: new top end.
Gearbox rebuild 2021 by Bears.

1979 Westerly GK24 24 foot racer/cruiser yacht Forethought of Gosport.
1973 wooden Pacer sailing dinghy