Powerplant and ancillaries
My plan was not to stray too far from the original factory specification for this build. The gearbox was upgraded to the 5-speed overdrive transmission from the 80's 320i, the suspension got some Ireland Engineering lowered Stage 1 springs and Bilstien shocks all round.
Matching-number engine rebuild
It's easy to check whether you have an original engine: the number on the block is identical to the one stamped on the body and VIN plate - life was simple back in the day! My plan was to do a stock rebuild and find a suitable Solex single-barrel carburetor to replace the missing one. I had to resist dreams of M Power and more cc's due to intervention from the intended recipient of the Baron (my wife)!
In technical terms the engine was pretty stuffed!
The turbo conversion and 40+years of use had left the bores at their limits, the head had been ground to below tolerance and was soft, now I really wanted my S14! In the end the decision was made to save it. So I did a total rebuild: liners, new pistons (grand pianos) oil pump, newish head - the lot.
Fuel injection and Megasquirt ECU
As luck would have it, my wife didn't sound too keen on a carburetor engine after all given her desire to have a fuel-efficient day driver. So out came the plans for an EFI upgrade, staying true to the BMW badge at the same time.
The majority of the parts come straight off the later e30 318i: air intake, fuel rail, in tank fuel pump, etcetera. The throttle body off the 325is the 318 injectors were replaced will higher flow ones. Fuel and ignition control will be managed by the MegasquirtMS3 with a MS3X expansion board. Update: The MS3X had some issues so after reloading firmware a few times I called it a day and ordered a MS2 and a EDIS module and coilpack, which in hindsight, I should have done in the first place!
The hardest part of this upgrade is finding a suitable place for all the components, the first major decision was where to put the battery? The battery tray position was needed to make space for the new air intake so it's either the trunk or under the rear seat. The trunk is easier but I wanted the space so back seat it was. I've opted to install to smaller Odyssey AGM batteries as although there is plenty of space, it's not a particularly useful shape!
Next was positioning the ECU and relay board for the fuel pump, injectors and cooling fan. I opted for under the passenger seat with easy access to plug in the laptop.
The ECU needs to reference the crank position to make all this work so I used a toothed wheel on the crank pulley and a VR sensor to pick up the signal and feed it to the Megasquirt. The 4 tower coil pack and amplifier supplies the spark, which was mounted on a custom bracket where the old distributor was. Update: Now replaced with the EDIS set up.
I could have spent days whittling up the required mounting plates for the larger throttle body, Idle Air Control, VR sensor, throttle position, fuel pump block off and distributor plug but fortunately a really helpful fella, Tom at www.02again.com had manufactured some high quality parts that did the job perfectly.
Wiring harness is courtesy of www.diyautotune.com which really simplifies things as Megasquirt is a real DIY tool and can be used to control anything from a lawn mower to a full on drag strip monster, which can make it seem pretty complicated at first.
Although this is clearly not stock, there is nothing that cannot be reversed back to original as I've kept all the original parts.