Capacitor Discharge Unit Questions
 

I am in the process of rebuilding my 1976 2.7 and am verifying I have all the parts. I have done a little investigative work on the C-D unit. So my understanding is this basically replaces the coil on a standard engine.

Oh, here is my C-D unit for reference purpose. The only number i can see on it is 9F 15-1-12V (so I guess this isn't a 6 volt system eh?) but I think this is a relay or something.

I labeled what I think things are, how'd I do? According to haynes (BW pic below), I am missing my CDS. I guess I would need this for the 2.7? Does it vary by model? What should this run me? Sorry for the basic questions. Still learning. BTW, looking at other photos online, it seems that some 911 engines have a regular coil, is this non-standard or only available on some models?

http://forums.pelicanparts.com/uploa...1322715374.jpg

http://forums.pelicanparts.com/uploa...1322716691.jpg

I think that is a defrost relay since your car does not have MFI there is no Speed Switch.

The CDS (or CDI, CDI Box... in Porsche nomenclature) does not REPLACE the coil. It feeds the signal to the coil. The CDI tells the coil to fire. The coil pumps up the 12V to spark levels, then fires through the coil wire to the distributor.

How can you tell what CDI you need? As far as I know, there are only two. One has a 3 pin connector, and one has a 6 pin connector. you should have a 3 or 6 pin plug sitting there as part of your wiring harness, that tells you what you need. 3 pin is earlier and 6 pin is later, but I do not know what the break was.

my 1977 stock CDI is 3 pin

Yes, you are missing your CDI (that is what we call it. The Factory called it BHKZ, for Bosch Hochspanner Kondensator Zundung, or Bosch High-Voltage Condenser Ignition).

The silver box is your defrost relay.

A 77 would have had a three pin box. You can find them used here for between $150-200.

If you search for "CDI" you will find a wealth of information.

The best coil to use is the original factory black coil, which has Bosch Nr. 0 221 121 001. Better to buy a used black one than the new silver Brazilian-made one.

Perfect. Thanks for the help. I will first check to make sure the engine is infact the 3 pin. Just to make sure and then I will go a hunting.