Wiring help request with MSD-6a

[Gerrys74Tii]

Setup: 74 tii (Korman 2-stage conversion to side draft Webbers), Pertronix ignitor system and Bosch Blue coil. I am installing a Bosch Red coil, MSD-6a and Tach Adapter and need clarification about the wiring: 1) where does the red/black wire from the Starter to Coil (in my current setup) interface with the MSD-6a? 2) which 12V switched wire is best to connect to the Pertronix (red,+) and MSD-6a red wires?

Thanks for any advise!

[Guest Anonymous]

Here's five pages of SEARCH results that may hold the answer . . .

http://www.bmw2002faq.com/content/view/60/61?cx=partner-pub-2478521489155222%3Aeolm2n-2i1w&cof=FORID%3A9&ie=ISO-8859-1&q=MSD-6a&sa=Search&siteurl=www.bmw2002faq.com%2Fcontent%2Fview%2F60%2F61%2F#1082

[JohnN]

http://lmgtfy.com/?q=msd6a+pertronix+wiring+diagram

John N

[Chris_B]

Any wire running from your starter to the coil is likely to be switched +12V (this car probably originally had a coil ballast resistor circuit with relay). Do you have a voltmeter? If this red/black wire has switched +12V, then you should use it to switch the MSD 6A (small red wire).

[Gerrys74Tii]

Thanks for your advise. I now recognize that the wire in question is the 12V switched wire that is was looking for (this red/black wire doesn't go to the starter but to the fuse box). All is hooked up now and working wonderfully! The Red coil, however, overheats and the car will stop running when warmed up. Guessing that I need a ballast resister in the path between the coil and Pertronix igniter or a newer igniter (my current one is 10-13 years old).

I'll need to research the forums to see how others have dealt with this same issue. In the mean time, any fresh ideas out there about the need for a resister in line with newer Pertronix igniters or other igniters on the market that you would recommend?

Thanks again!

[Chris_B]

You do not need a ballast resistor when using the MSD ignition. To quote from the MSD wiring install manual: "A ballast resistor is not necessary with any MSD Series Ignition but can be left in-line if originally equipped."

If your coil is crapping out when it gets hot (presuming it is wired properly), it is probably FUBAR.

[frank]

Mine is installed with no resister, and I changed from a bosch blue coil to MSD's coil. Works great.

[Gerrys74Tii]

Thanks! I love this Forum. I called the folks that sell the "Ultimate Spark Package" for the 2002 (Top End) about the need for a resister with the Bosch Red coil. They confirmed that no resister was needed with the MSD-6a with Bosch Red coil setup. However, after reading most all the information on this site, I remain confused as to why no resister is necessary. What does the MSD do that makes a resister unnecessary? Does the MSD regulate the voltage delivery to the coil and thus eliminate coil overheating?

Also, Frank, I am wondering about the use of a MSD coil over the Bosch Red or Pertronix Flamethrower (with resister). The MSD delivers 45,000 V whereas the others deliver 40,000 V and appear to have different secondary windings and other specs. I like the possibility of using all MSD ignition products together. Does MSD make an ignitor for the 2002? I didn't find one in their product listings.

Thanks again for your advise and experience!

[Chris_B]

Yes, the MSD does control voltage delivery to the coil. However, I dunno about the inference you are making between presence or lack of a resistor and coil overheating. In any event, it is a moot point if you are using the MSD 6.

[Gerrys74Tii]

Thanks Chris. I installed the Bosch Red coil and all seems A.O.K. so far.