Write-Up
VEMS Genboard on a BMW E30

Before you start, here are some very important points to remember:

  1. Download latest firmware and MegaTune (yes, the same program that you tune MegaSquirt with is used for VEMS Genboard)
  2. Install MegaTune and learn the interface, while reading the online VEMS manual
  3. Create an ECU "fuse box" controlled through a relay and a 20A fuse, then use separate fuses for:
    [Picture of fuseholder]
    • VEMS Genboard (3A)
    • Wide-band lambda sensor (5A)
    • Injector harness (10A)
    • Ignition coil (10A)
    • ICV (5A)
  4. Establish a solid chassis ground for the VEMS Genboard signal and power grounds.
    http://vems.hu/manual/html/ch08.html
  5. Connect sensors and grounds:
    • IAT - Intake Air Temperature
      Use any open air sensor you can find or fabricate one from the cheap NTC resistor in the VEMS Webshop. More info on cheap custom installs here:
      http://www.vems-group.org/wiki/index.php?page=GenBoard%2FManual%2FIntakeAirTemperature.
    • CLT - Coolant Air Temperature
      Besides the trigger, this is the only stock sensor that you can use as is.
    • TPS - Throttle Position Sensor (needs calibration)
      It is recommended that the on/off type TPS that is on the BMW E30 is replaced with a potentiometer type from a more modern stock EFI system. However a resistor grid can be made to simulate three different positions, as the exact position is rarely needed and acceleration enrichment can be had through pressure instead. Here is a link to a schematic on how to keep the stock TPS:
      http://www.vems-group.org/files/Marteleur%20Tim/TPS3.JPG
    • MAP - Manifold Air Pressure (needs calibration)
      When you purchase the Genboard you can choose between having the MAP sensor mounted internally or externally, just draw a pressure line to it.
    • Trigger - Inductive sensor on primary input
      The inductive sensor on the front of the Motronic engine uses a shielded wire with green plastic cover, this must be ripped out of the stock Motronic harness and connected to the primary trigger input.
    • WBO2 - Wide-Band Oxygen Sensor
      The Bosch LSU4 is found in the webshop and must be used with a special connector (also in the webshop). This is then wired to the EC18 connector of the VEMS Genboard case.
  6. Connect injector power to the fuse block and "flyback" power back to VEMS Genboard
    http://www.vems.hu/manual/html/ch10.html
  7. Connect ignition coil or coils. Note: You might want to use wasted spark coils and discard the distributor.
    http://www.vems.hu/manual/html/ch12s02.html
  8. Connect ICV
    http://www.vems.hu/manual/html/ch11s03.html
  9. Double check and measure the harness and basic functionality with a digital multimeter.
  10. Insert fuse for VEMS Genboard and check the basic sensor functionality:
  11. Insert fuse for wide-band lambda sensor and calibrate it
    http://www.vems.hu/manual/html/ch09s06.html
  12. Insert fuse for ignition coil and turn over the engine, verify/check ignition timing and order using a timing light (strobe). Use markings on the flywheel to see which cylinders are at TDC.
  13. Insert fuse for fuel injectors and ICV.
  14. In case of different sized injectors - crank and tune inital fuel settings
    • Priming pulse (start at zero)
    • Cranking pulsewidth (increase until it sputters then dies above set cranking rpm)
  15. In case of different sized injectors - tune running fuel settings
    • Required fuel (req fuel)
    • VE table
    • Lambda table
  16. In case of stock engine
    • Turn over the engine and hear it roar

All of this is of course simplified by a provided initial configuration of the VEMS Genboard with default settings for everything. It should basically crank and start a stock M20B25/B20 with stock injectors and a single coil with distributor. Small change required for wasted spark coils (no distributor).

Some issues to solve are:

What do you think? Any major points missing?

It is your choice to use the stock harness - the big issue about that is the power to the injectors, which I think should be controlled through the fuse box built in the initial steps. A stage 2 setup after everything works might be a full custom harness to remove all the Motronic crap.

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