Excellent Thread !!

Jon,

Can't thank you enough for all of the leg work that you are doing on this!! It will go a long way toward helping us keep these old systems running. And, even more importantly, providing insight into what's going on when they don't.

For the last 20 years or so, I have typically used the Echlin line of ignition parts from NAPA on any breaker point ignition vehicles. I have not personally experienced any condenser failures - although I will be the first to admit that my sample size is very small, and do not put nearly the number of miles on these vehicles as many others on this site.

Regarding the quality of available condensers today, I appreciate your statement about the potential issues related to the overseas "manufacturing of small electronic parts not enjoying high consumer demand". Very well stated. Unlike a smart phone or TV, which is made in some huge, modern, automated factory, it would not surprise me if these are made in some guy's garage, with minimal understanding of the fundamental design concepts, using 50 year old tooling and technology.

I think you are right on regarding your search for capacitors that use newer capacitor technology. No secret that significant improvements have been made over the last 20 - 30 years.

I also think that the main challenge will be packaging. It's hard to beat the convenience of having that nice compact metal encased single lead capacitor sitting there on the breaker plate.

I'm not quite as concerned about other factors such as temperature. Many of these capacitors are used in motor controls or other circuits that may experience elevated temperatures. How hot does a distributor really get? If you throw water on it does it turn to steam? Probably not, but it would be interesting to see some actual temperature data. Same with voltage rating. Lots of offerings out there in the appropriate range.

It would be interesting to see the original requirements from the likes of Delco Remy, or other ignition manufactures for the capacitors used in their distributors. I would be willing to bet that most are way below what is available today, or the offerings that you are investigating.

It would be great if some entrepreneur somewhere would take this on. I would easily pay several times the current cost of a condenser if I new that it offered better reliability.

With regards to whether or not the capacitor would be fast enough, assuming no change in the coil or other primary ignition system components, the value of the capacitor is what really determines that, right? It's the "C" in RC time constant - which is indicative of how fast the capacitor in an RC circuit can charge / discharge. So, I'm thinking that as long as you keep close to the original value, you will be OK.

Jerry's point regarding the function of the capacitor is well taken. Back in the Dark Ages, when we first learned about breaker point ignition systems, the purpose of the condenser was usually just explained as: "It keeps the points from burning up." In reality, it is more complicated then just that.

This link is from a college EE lab that actually deals with the physics of ignition systems. It is pretty interesting.

Physics of Automotive Ignition Systems

The paper states that the sizing of the capacitor is important, in order to match the resonant frequency of the coil. The idea is to create an RLC circuit which increases the emf in the primary, which in turn increases the available voltage in the coil secondary. It would be interesting to scrounge up some of the test equipment shown in the lab, and verify this assumption.

I have BTW, seen this in other papers on ignition systems. However one thought always comes to mind: What about electronically controlled ignition systems such as HEI? I don't ever remember seeing a condenser attached to them - just the control module. Based on the size (in uF) of the condenser, I doubt that it could have been packaged inside the module. Maybe they found another way, or were just able to get around the problem entirely by increasing the coil primary current.


Best Regards….