Automobile Work, Automobilia

Alfa Romeo Coil Upgrade

Many owners of vintage Alfas change out the mechanical distributor with points to a modern electronic version. 123 Ignitions make a very nice one for Alfa 4 cylinder  engines. Using this system offers more flexibility in advance timing and spark plug gapping. A larger spark plug gap provides better burning of the fuel mixture. Most often a Bosch “blue” coil is fitted along with the new distributor.  Fitting a Blue coil is a waste of the 123’s capabilities. A 123 + blue coil makes lower energy sparks than a points distributor with a marelli coil and ballast resistor. Below is a graph of current vs energy for these and other combinations. The 123 limits current to 6 amps but the Blue will only allow it to pass 4 amps. Also, the high inductance of the Blue coil causes coil current to fall quite rapidly with increasing rpm. The Bosch blue coil is manufactured in Brazil and is quite unreliable and low quality.  A good, high-powered replacement is the MSD Blaster Coil.

Installing the new high powered coil requires a ballast resistor. If the coil is to be mounted horizontally a “high vibration” coil is required. Vertically the standard Blaster 2 coil will suffice.

Hook up is follows:
Green/black wire is joined to 123 red wire and then connected to one side of ballast resistor.
The other side of ballast resistor connects to coil positive
The black wire from the 123 connects to coil negative.

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