TI coils vs. regular

[Duke W.]

Re: TI coils vs. regular

This latest Petronics 3 is also supposed to have multi spark which I think is ??? at best.. Can't time a car with it, at least I have not figured it out.

For most of our cars good points work fine. The breakerless upgrade seems to be a very good switch that does not yield to the resistance points can have as they wear. I am happy with the breakerless and the way the car runs. I even cleaned a old set of AC44's and installed them, no problems..

If more than one spark is required, there's something wrong with the system design.

Car manufacturers always use inductive ignition systems because they generate long duration sparks, which is the best type of spark to ignite lean, low density, or exhaust gas diluted mixtures, which is typical of road engines that spend most of their at relatively low load or idling.

CD ignitions have very intense, but short duration sparks. They work very well with rich, high density mixtures typical of racing engines at WOT, but not with lean, low density, diluted mixtures.

The GM point ignition spark duration is about 120 microseconds. TI and HEI are about 180, but the CD system from the late sixties was only about 35, and the MSD system is probably about the same. Though it generated "multiple sparks in the low to mid rev range, if the first one doesn't light the fire, the second is considerably retarded.

Duke

[Jack H.]

Re: TI coils vs. regular

Didn't Pontiac also try CD back in the late 50's? I seem to remember coils and distributor caps that were stark raving PINK in color supporting these ignition systems, Duke...

[Duke W.]

Re: TI coils vs. regular

The CD ignition's first year as an option was 1967. Olds offered it, but I'm not sure about Pontiac. It incorporated the same mag pulse dist. at TI, but the special cap was bright red. I think the external box was red, also, and it may have also incorporated special plug wires.

It only lasted for two or three years. I'm not sure why it was dropped, but possibly because it was not really a very good system for a road car due to the short duration spark, or it could have just been poor sales. I don't recall the option price, but it must have been at least as much as the TI and maybe more.

Duke

[Jack H.]

Re: TI coils vs. regular

I was wrong about Pontiac and CD. This quote comes from another web based site:

"Delco-Remy first developed their new transistor controlled ignition system for the full-size Pontiac 389 and 421 engines on 1963 models. Throughout the 1960's, various cars could be ordered with a TI system including Corvettes, full-size Chevrolets (including the 409), Chevelles, Chevy II's, and eventually as an over-the-counter (OTC) setup to install on any Chevrolet small or big block engine. The 1969 aluminum block ZL1 was the only Camaro that came with a factory installed TI system."

[Clem Z.]

Re: TI coils vs. regular

i believe the difference is the turns ratio between the primary and secondary winding are different in the TI coil vs the standard coil