BMW M44 engine ignition coilpack

This is a 4-pack coil block. It has a special round 7-pin

connector (6 pins used). (I have the opposite side connector and harness also)

Measured pinout:

- pin 1 - IGN channel 1 (white wire)

- pin 2 - +12V (thick green wire)

- pin 3 - GND in harness (brown wire)

- pin 4 - N/C

- pin 5 - IGN channel 4 (blue wire)

- pin 6 - IGN channel 2 (red wire)

- pin 7 - IGN channel 3 (yellow wire)

- Measured primary coil resistance is 0.5ohms.

- Interestingly there was a GND connection in harness but I couldn't measure this pin's resistance to any point of the coilpack. Wire shielding is another extra wire not connected here.

Dwell measurement

I've measured ignition current to guess possible dwell times on bench setup: 12.3V from battery, measured AC voltage on 0.1Ohm series resistor.


At this voltage level (in the resistant phase it's 12.3V*(0.5Ohms/(0.1Ohms+0.5Ohms))= 10.25V it seemed that the coil is charged at about 7ms

Interestingly the spark rate got halfed when I adjusted dwell over 8ms. No other thing was changed and it was consistent: spark rate was ~120ms -with the setup I used- when dwell > 8ms and ~60ms when dwell < 8ms. Is this a bug or some strange feature? (firmware ver 1.0.38)

Question: what dwell time it would be if voltage is ~13.5V and how much it's affected by the 0.1ohms series resistor.