BMW E21 Bespoke Harness & MaxxECU Install

This BMW E21 Euro import came to us after being converted from carburettors to ITBs, needing a complete wiring solution and standalone ECU to make it all work properly.

As the car was originally carbureted, it didn’t have provisions for an electric fuel pump, cooling fans, or engine management. We designed and built a full custom wiring harness to suit, based around a MaxxECU Street ECU.

With no off-the-shelf options available, we produced a custom trigger kit in-house, including a trigger wheel and sensor mount, to give the ECU a reliable engine speed and position signal.

To support proper fueling control, we added a lambda boss to the exhaust and installed a wideband lambda sensor, allowing the ECU to run closed loop fueling.

We managed to tuck the ECU under the dashboard inside the interior, despite the lack of avaliable space!

We also made a coil pack mount and a set of custom HT leads to suit the setup.

The car left us with a complete, working wiring and ECU system in place, ready for final mapping once some other mechanical work was finished.