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In the Beginning – Points and Condenser

Almost all of my hobby cars were at one time equipped with points and coil ignition system. I’m not going to go into the theory of operation in this post, but I will offer the opinion that if your car has this ignition setup make your life easier by getting rid of it. From the moment points are installed, their performance begins to degrade. The contacts start to pit and the cam follower begins to wear, changing your gap. In addition to point gap, you have to worry about getting the proper dwell. The pivot and cam follower need to be lubricated periodically and you have to be sure the breaker plate is a good electrical connection to battery ground. Early car makers didn’t use these things because they were wonderful – it was all they had back in the day. Like carburetors, there’s a better way to get things done, but going to an alternative for carbs is tough. Switching to modern ignition is a no-brainer. Now that I have ticked off all of the purists, let’s look at the ignition updates I have employed and, keep in mind, there are others.

The Basics – Aftermarket Electronic Ignition

I subscribe to a lot of classic car forums and FB groups and I can count on finding some discussion about ignition systems and related drivability problems. Some folks want reliability while others cherish originality and want to keep their points and condenser systems going. Since they started being available on the market, I have been a proponent of electronic ignition conversions. Systems like Pertronix have been around for years and, for the most part, the units are hidden from view and don’t affect the originality of the car appearance-wise. You can buy a complete distributor with electronic “innards” as they say, or you can just replace the mechanical points and condenser with a small module that uses a hall effect sensor for triggering the spark. Like any subject on the interwebs, the discourse usually has opponents who say something like “I tried those !@##$ electronic things and they are all garbage!” This has not been my experience. Instead, these units have removed one impediment to the reliability of my inherently unreliable car collection and allowed me to concentrate on other vehicular projects. The Pertronix website contains a wealth of info and application charts. If you decide to go this route, follow the instructions and make sure your coil is the proper resistance or you will burn up the unit and end up saying “I tried those @#$%^ …” and so on.

Okay, don’t take my word for it. Check out this video from Bugeyeguys, the preeminent restorers of bugeye sprites and other classics. They have installed Pertronix distributors on over 400 cars they have restored.

A Bold Step Forward – CDI

Back in the 70s, I became interested in capacitor discharge ignition or CDI.  The principle of CDI is rather than make and break a 6 or 12 volt feed to the coil primary, why not fire a high voltage pulse of around 40 or 50 volts across the coil?  An inverter pumps the 12 volt battery voltage up to 50 or so volts which is used to charge a capacitor.  A signal from the distributor tells the capacitor to discharge across the coil primary.  BAM! as Emeril would say.  The history and operation is explained on this great web page.  A co-worker of mine had built a home-brew CDI unit in a really ugly Masonite box, about a 4 inch cube, and lost interest once he had proved he could do it.  I took it and mounted it in whatever derelict vehicle I was driving at the time (TR4 maybe?) and lo and behold, it worked.  It still used points, but the amount of current pulled across the contacts is greatly reduced, thereby eliminating pitting, which is one of the many things that ultimately destroys points in a conventional system.  My makeshift system, like all early electronic systems in cars, suffered from exposure to the heat and harsh environment under the hood.  CDI systems improved over the years, shrank in size and ultimately became an industry standard still in use today.

LIGHTNING! – Multi-Spark Discharge

I bought my current TR6 around 1985. I spent a few weeks doing some engine swap stuff and, at some point, started looking for an ignition upgrade like I always do. Eventually come across a unit from MSD that promised to fire the plug multiple times on each power stroke. This pushed all my tinkerer buttons, so I dove in, installed it on the car and as they say, the rest is history. I didn’t have any way to quantify its performance, but subjectively I remember thinking that the idle was smoother and the car seemed to have better low-end torque. And it looked WAY COOL! Time passed and I did stuff like replacing plug wires dizzy cap, rotor, but just taking that red and silver box for granted. The year 2021 rolls around and it occurs to me that I’ve never given this thing much thought and I honestly wasn’t sure what it was doing other than firing the plugs in a surprisingly reliable fashion ( and looking older but still WAY COOL, like its owner). I decided to whip out my pocket oscilloscope (everbody’s got one, right?) and take a look at what the MSD is sending to the coil.

What I found was shocking! Well not really, but it was gratifying. At idle I was seeing four 1 millisecond pulses for each plug. It says the total amplitude of the events is 48 volts. Not too shabby. You can trigger the MSD unit with the original points, but my car is using an optical shutter that came with another system I experimented with. So much for the primary side – what’s happening on the secondary side? To find out, I decided to break out the big gun, our Autel scanner with four channel Bluetooth oscilloscope. Kind of overkill, but I killed the battery on the pocket scope taking that last picture

The Autel comes with an inductive pickup for the secondary that clips onto a spark plug wire. There are a LOT cheaper ways to do this, believe me.

Anyhoo, here’s a screenshot of the secondary waveform and , as expected it mimics the primary signal. So, every time a plug fires, it actually fires four times, which seems like a good thing. Just a note in closing. You still need to insure that the distributor advance systems are working. With the cap off, twist the rotor and it should move a few degrees and spring back. If not the cam may be seized on the distributor shaft. Also check that the advance diaphragm does not leak and that it actually moves the breaker plate. Happy motoring!