Applications:
VW used quite a number of ignition systems on their water cooled engines. This article covers the Hall effect distributor with four teeth, used on most of the ’80s era inline 8V and 16V motors. Later VWs used a 60-2 crank trigger to drive a distributor, or later, distributorless ignition systems. This article covers the older 4 vane distributor and the Bosch 139 module.
Note: We’ve confirmed that the flat four “Wasserboxer” engines as used on Vanagons use a different ignition system. The coil is controlled directly from the ECU, and it is not yet confirmed if the distributor input mods work with the stock distributor. Right now this article is only confirmed to work on inline motors.
With a K-Jetronic (CIS), you will also need to swap your fuel system over to EFI. The other EFI systems – L-Jetronic, Motronic, and Digifant – can use their stock hardware.
The Bosch Hall effect distributors let you use almost any MegaSquirt variant out there.
What’s covered in this article
Note that our tech ‘Install Articles’ typically focus on the most confusing part of the install process for the end user, and that’s taking control of the ignition system. This is the part of the process that’s different from car to car and hence we chime in with specifics to help where we can. For the rest of the details, the parts that are the same on every car like the coolant, intake, TPS, and o2 sensors, see the wiring section of MSExtra.com.
Using the MegaSquirt-II PCBv3 with the Bosch 139 ignition module
MegaSquirt-II PCBv3.0 Mods Required:
- Build the Hall effect input conditioner circuit, as described in MSExtra’s MS2 Manual. All our preassembled MegaSquirts with the V3.0 board come with this circuit installed.
- Jumper TachSelect to OptoIn
- Jumper TSEL to OptoOut
- Jumper XG1 to XG2
- You’ll need a 1K pull-up resistor from the 5 volts in the proto area to TachSelect
- Jumper JS10 to IGBTIN
- Install a BIP373 or TIP120 in the Q16 slot, using a mica insulator
- Jumper IGBTOUT to IGN
- Add a 1K pull-up to 5 volts by connecting a 1K resistor from the IGBTOUT-IGN jumper to a 5 volt supply from the proto area
MegaSquirt-II PCBv3.57 Mods Required:
- Put the XG1 to XG2 jumper in place across both pins
- Put JP1 in the 2-3 position and J1 in the 1-2 position
- Solder a 1K resisor across the R57 pads
- Jumper JS10 to IGBTIN
- Install a BIP373 or TIP120 in the Q16 slot, using a mica insulator
- Add a 1K pull-up to 5 volts by connecting a 1K resistor from the center leg of Q16 to a 5 volt supply from the proto area
External Ignition Wiring
- Connect the signal wire from the Hall effect sensor on the distributor to pin 24 (Tach on the relay board, if used)
- Connect the #6 pin of the Bosch ignition module to the MegaSquirt’s pin 36
TunerSudio Configuration:
- Trigger offset = 60 (this will vary, depending on the distributor orientation, see notes at the end of the article)
- Ignition Input Capture to ‘Rising Edge’
- Cranking Trigger to ‘Trigger Return’
- Coil Charging Scheme to ‘Standard Coil Charging’
- Spark Output to ‘Going Low (Normal)’