Bosch Red Coil on 2.2T 1970

[WMontald]

Hello,

There are some posts on the Bosh red coil , but none off them are clear if it works,works with original CDI, and how to add/place additional resistor.
Does anyone have experience with this type of coil on an early 911 2.2T from 1970.

Many thanks

[id911T]

My 70T came to me with a Bosch blue coil installed and it made the tach go crazy. Both the Blue and Red coils are designed for inductive ignitions and aren't suitable for use with our CDI's. Once I installed the proper CDI coil all was well.

[Bob Ashlock]

If you are running the original Bosch CDI unit, you need to use the transformer (coil) that it was intended to work with. This low inductance coil insures optimal spark energy. You want an original BLACK Bosch coil part number 0 221 121 001 (stamped on the bottom). The originals are harder to find, often you will see the same part number offered in a SILVER (aluminum) version, made in Brazil. Those are notorious for short life, develop internal arc paths that result in low or no output, so I tell people to avoid them. I have heard that Bosch recently improved them, but no direct confirmation of that. I have had good results with the aftermarket version of the original coil made by Parts Klassik. The general parameters of that coil closely match the original Bosch.