BMW 1977 to 1983 320i E21 simple breakdown

1977 - 2.0 Ltr, Vented front disk brakes and larger front bearings, Used K-Jetronic (CIS)
1978 to 1979 - 2.0 Ltr, Sold front discs and smaller front bearings (can but updated to '77 specs since they are on the same spec line)

1980 to 1983 - 1.8 Ltr, Same brake setup as the 1978 to 1979 cars but can not be updated to the '77 spec since they are on their own line. Used Bosch KE-Jetronic (CIS-E)

The K-Jetronic is fully mechanical injection system. Getting your fuel and control pressures correct is the main key to this system.

The KE-Jetronic has a narrow band O2 sensor and a simple ECU that controls a frequency valve that adjusts the control pressure in the fuel distributor to keep the AFR at 14.7:1. By replacing the 02 sensor with LC-1 from Innovate Motorsports, you are able to tune the engine for more power by adjusting what the ECU thinks is the current AFR ratio.

I do agree that if you wanted to run a BMW in ITB the 1984 to 1986 E30 318i is the better choice. The E30 has the same basic motor as the later e21 but the injection is fully electronic. The compression ratio is higher then the E21s. The e30 chassis is better then the E21 and has a lower weight.

I have raced a 77 320i for a number of years in ITB and BMWCCA club racing.