TI coils vs. regular

[Michael J.]

Does anyone know if the various TI coils for C2s (originals or repops) have any different electrical characteristics than a non-TI coil from the same vintage? In other words, are they interchangeable. Thanks for any info.

[Chris H.]

Re: TI coils vs. regular

Michael, in a word "no", they are not interchangeable. When I first purchased my '65 396, it would start to break up at 4000 rpm. Turns out the previous owner had installed a non-TI coil. As soon as I put a TI coil in there, the motor pulled clean to 6500 rpm. I'm sure some electrical gurus out there can comment to the differences in coil construction.

[Michael J.]

Re: TI coils vs. regular

OK, thanks, I was afraid of that. I also found a detailed decription in the archives about how the TI coil has opposite polarity from regular, and the voltages supplied are different too. So guess I will just lose the points.

[Mike Z.]

Re: TI coils vs. regular

Michael-
The TI coil has heavier wire and more windings-reason: the TI amp inputs a higher than conventional ignition primary voltage (DC) which then is amplified and converted to very high AC (pulse voltage). The typical conventional system generates somewhere in the 20k-25k on a good day, but the TI system is good for up to about 42k volts. Feeding the higher primary voltage into a conventional coil will probably cause it to over heat and boil out the cooling oil and ultimate failure-and will not generate the extra voltage mentioned because it does not have the windings to do it.
Reproduction TI coils are readily available on E-Bay at reasonable cost and they work great-I have run one for about eight years, no problem. The TI is a great system-good luck.
MichaelZ505

[Duke W.]

Re: TI coils vs. regular

The TI coils have different primary and secondary resistance, and it's listed in the '66-up CSMs during the period that the TI system was an option.

Open circuit voltage is meaningless. In an operating engine with spark plugs in reasonable condition, the spark forms at about 5-10K volts, and then the voltage across the gap drops to a few hundred volts until the spark stops. If more than 15K volts is required to initiate the spark, something is wrong.

What really counts in an ignition system is the per spark energy measured in millijoules, and the TI is nearly double the single point system - 74 vs. 41. The open circuit voltage of the TI is 30.0 kV vs. 24.0 for most versions of the single point system, and this is reflected in the higher primary current of the TI. The HEI has very similar engineering specs. It's basically a compact version of the TI with the electronics packaged in a single hybrid module inside the distributor rather than an extenal "box" with discrete components.

The above data is from a SAE paper on the CD system written by GM engineers. The short lived CD system was used by Olds and maybe some other divisions. Chevrolet never used it to my knowledge, but both systems used the same basic mag pulse distributor.

The CD system utilized a special coil with different resistances than either the single point or TI.

Duke

[Michael J.]

Re: TI coils vs. regular

Thanks for the info everyone. I have been thinking about putting a TI back in my '67 L71, as it was converted to Petronix and runs great. In looking through the archives, threads like this one:
https://www.forums.ncrs.org/showthre...53320&uid=7154
Tell me I probably don't want to do it, too many problems, thousands of $$, and only a few extra points on flight judging since the TI is 6 points total and the coil is 10 points total (O+C). So I think I will just let it be.

[Wayne M.]

Re: TI coils vs. regular

Reproduction TI coils are readily available on E-Bay at reasonable cost and they work great-I have run one for about eight years, no problem.

Speaking of eBay repros (the ones licenced by GM), does anyone believe or has checked that (other than the number embossed on the can) there is any measureable difference in the electrical properties, or in the performance among these T.I. coils ?

[Joel F.]

Re: TI coils vs. regular

Speaking of eBay repros (the ones licenced by GM), does anyone believe or has checked that (other than the number embossed on the can) there is any measureable difference in the electrical properties, or in the performance among these T.I. coils ?

Wayne,

Is there more than one manufacturer of these coils? If so, do you suspect they have different operating properties? I assumed the repro TI coils were all made by the same manufacturer.

[Mike Z.]

Re: TI coils vs. regular

Wayne, in my first reply to this thread I tried to keep my input basic to where a new or less knowledgeable member might understand, with the bottom line being conventional and TI coils are different. Duke replied with a very technical response regarding resistance, which is very good and all true. I would like to, however, respond to your specific question regarding the reproduction coils I suggested one might buy on E-Bay, including from me-specifically the Delco licensed reproduction coils. Although, they are manufactured overseas, they were engineered and tested prior to and during the production runs, here in the States. I will try to summarize information I have been provided, but I am not an expert by any means. The operation and consequently the testing of an ignition coil is more art than science. There are events such as kv output, rise time, arch duration and carbon tracing that come into play. In a short answer, these reproductions equal or surpass the performance of a new OEM equivalent (TI or convention depending on application)-it is not just the embossed part number that they have tried to duplicate-remember, they are licensed by Delco.
What I found interesting; it is not necessarily the voltage to be concerned with-Duke was right in that it comes down to resistance. Take a new coil, set of spark plugs and wires-because they would have low resistance (may require only 5kv to overcome resistance), the spark generated from the coil, seeking the path of least resistance, will travel through the wires and ignite the spark plug-just as designed. Now, take those same parts (including the coil), several miles and years down the road and guess what, they will have developed greater resistance-therefore, the spark may not end up where it was designed to go-the result is a high speed miss. Replacing the spark plug and/or wires may cure the problem, but over time a process within the coil called carbon tracing develops, which also can cause a high speed miss (spark seeking the carbon traces within the coil). That's why back in the day, mechanics would change out coils routinely-they may not have understood the why, but they knew the cause all too well.
The TI & conventional coils are different: TI has thicker wire, more windings and more oil than a point coil. The oil is another factor in all this-if a coil is overheated there is the chance of the cooling oil to boil out, which will result in the possibility of a winding shorting out, and ultimate coil failure. These Delco licensed reproductions have been vacuum filled (like the original process), not simply filled and wait for the bubbles to evaporate like a certain re-builder of original coils does. With the additional features of the TI coil, it is capable of overcoming greater resistance (right, Duke?): in a comparison; a conventional ignition system is maybe capable of 20-23kv vs. the TI is capable of 35-42kv to overcome any resistance, giving the TI system a better chance of not having a high speed miss or igniting a fouled plug-ever had a Big Block? you have to like changing plugs; albeit, much more often in a point ignition car.
So, to summarize: what do want to run in your car ?; a 50 year old coil of unknown capabilities or a brand new reproduction with known quantities? As I indicated, I have run these coils for a few years and neither of my 66's lost points at the National level with them. I have no hesitation suggesting the use of these coils, and yes, if you run a TI-you need to run a TI coil.

MichaelZ505

[Gene M.]

Re: TI coils vs. regular

MichaelZ505,

Would running a TI coil in a regular points system but substituting a pertronix module for the points, without the ballast resistor be of any benefit?

[Michael J.]

Re: TI coils vs. regular

MichaelZ505,

Would running a TI coil in a regular points system but substituting a pertronix module for the points, without the ballast resistor be of any benefit?

That's a good question, is the extra voltage going to fry something on a regular petronix system, or would the higher voltage be a plus?

[Mike Z.]

Re: TI coils vs. regular

Gene-
In the GM K-66 system, 12v. DC is introduced into the system via the amplifier during start mode only. In the run position, voltage delivered to the amp/coil is about the same as convention level of approx. 7v. DC. Yes, the TI system (K-66) did not run a ballast resistor, but the harness has a resistance wire within the harness that accomplished the same thing.
I feel the Pertronix Ignitor pointless system is a trigger system (replacing points) and nothing more. The benefit is possibly a more stable trigger system, with no wear, but the system contributes no additional or enhanced properties. Therefore, pumping 12v. into a coil designed to run on 7v. continuous will most likely overheat the coil with dire results (read failure). Guess one could spend the big money for their Blast Coil to go with their "Ignitor" they push on their web, but here again, without the TI amp as the "gate keeper", all you really have is a more expensive conventional system.
In the K-66, voltage is increased and converted (DC to AC pulse) twice within the amp housing (varies depending on load and resistance factors), making it capable of working with the TI coil to create the benefit of not only greater kv, but also greater spark duration and sharper rise, which a conventional system with or without Pertronix is NOT capable of. If you want the benefits of a better trigger system and better resistance capabilities, step up to a TI system.

MichaelZ505

[Duke W.]

Re: TI coils vs. regular

Wayne, in my first reply to this thread I tried to keep my input basic to where a new or less knowledgeable member might understand, with the bottom line being conventional and TI coils are different. Duke replied with a very technical response regarding resistance, which is very good and all true. I would like to, however, respond to your specific question regarding the reproduction coils I suggested one might buy on E-Bay, including from me-specifically the Delco licensed reproduction coils. Although, they are manufactured overseas, they were engineered and tested prior to and during the production runs, here in the States. I will try to summarize information I have been provided, but I am not an expert by any means. The operation and consequently the testing of an ignition coil is more art than science. There are events such as kv output, rise time, arch duration and carbon tracing that come into play. In a short answer, these reproductions equal or surpass the performance of a new OEM equivalent (TI or convention depending on application)-it is not just the embossed part number that they have tried to duplicate-remember, they are licensed by Delco.
What I found interesting; it is not necessarily the voltage to be concerned with-Duke was right in that it comes down to resistance. Take a new coil, set of spark plugs and wires-because they would have low resistance (may require only 5kv to overcome resistance), the spark generated from the coil, seeking the path of least resistance, will travel through the wires and ignite the spark plug-just as designed. Now, take those same parts (including the coil), several miles and years down the road and guess what, they will have developed greater resistance-therefore, the spark may not end up where it was designed to go-the result is a high speed miss. Replacing the spark plug and/or wires may cure the problem, but over time a process within the coil called carbon tracing develops, which also can cause a high speed miss (spark seeking the carbon traces within the coil). That's why back in the day, mechanics would change out coils routinely-they may not have understood the why, but they knew the cause all too well.
The TI & conventional coils are different: TI has thicker wire, more windings and more oil than a point coil. The oil is another factor in all this-if a coil is overheated there is the chance of the cooling oil to boil out, which will result in the possibility of a winding shorting out, and ultimate coil failure. These Delco licensed reproductions have been vacuum filled (like the original process), not simply filled and wait for the bubbles to evaporate like a certain re-builder of original coils does. With the additional features of the TI coil, it is capable of overcoming greater resistance (right, Duke?): in a comparison; a conventional ignition system is maybe capable of 20-23kv vs. the TI is capable of 35-42kv to overcome any resistance, giving the TI system a better chance of not having a high speed miss or igniting a fouled plug-ever had a Big Block? you have to like changing plugs; albeit, much more often in a point ignition car.
So, to summarize: what do want to run in your car ?; a 50 year old coil of unknown capabilities or a brand new reproduction with known quantities? As I indicated, I have run these coils for a few years and neither of my 66's lost points at the National level with them. I have no hesitation suggesting the use of these coils, and yes, if you run a TI-you need to run a TI coil.

MichaelZ505

It would REALLLLY help if you broke the above into several paragraphs by using the return key to make paragraphs with a space in between them. A solid screen of single spaced text is just plain unreadable.

As I said, the open circuit voltage I quoted was from a SAE paper written by GM engineers, and I'll take that for fact.

Duke

[Timothy B.]

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..

[Michael J.]

Re: TI coils vs. regular

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..

Exactly, but why then would anyone want to replace those with a repop TI system and take the risks?