- V12 60 degree even-fire
- maximum RPM is: 3500 rpm
- Mounted in a boat (pro-longed high load compared to a car)
- Two spark plugs per cylinder, total 24 spark plugs (12 wasted spark coils)
- Two cylinder heads, each having inner and outer bank of plugs.
- Each bank uses one Bosch Motorsport 3x2 coilpack (4 pcs required for one engine)
- Beru 3-channel ignition modules (min 10 mA drive current)
- One fuel injector per cylinder
- Siemens High-Z 9 Ohm fuel injectors
- 24-1 crank mounted trigger wheel (or 24-2 is also OK)
Due to lack of outputs I will handle the engine electrically as an inline 6 cyl.
Two injectors per injector output.
- Can one FET handle sustained high duty cycle with sufficient cooling?
- yes, 100% duty upto about 5 (or even 6A) is OK. (the FET's peak current is about 14A but we specify much lower)
- Two injectors 9 Ohm results in 4.5 Ohm @ 14 Volts = 3 Amps
- yes, 3A is no problem at all. Make sure to connect flyback wire, of course.
Driving the ignition modules
- Drive current requirement per ignition module input is minimum 10 mA
- Driving two channels is a minumum 10x2 = 20 mA up to 40 mA.
- Can the IGBT logic driver handle this? 20mA : yes, 40mA: no (but 40mA should not be needed anyway)
- Suitable resistor values on board?. 255 Ohm is suitable to drive one module, but 120-130 Ohm (=510x150-160 Ohm or so) needed to drive 2 modules (that still protects the i259 chip's outputs)
- Stepper outputs are powerful, but current limiting resistors (100-200 Ohm) are recommended to protect from short circuits
Ignition output hardware configuration
6 IGBTs and 2 logiclevel outputs
- It can be decided later to use logiclevel or power-outputs.
- Option 1 : 6 outputs required - using 4 stepper outputs and 2 logic level outputs
- This is the method we will try first using external ignition modules to avoid ignition coil current through ECU ground
- Option 2 : using 4 stepper outputs (with module driving 8 transformers) and 4 IGBT outputs driving 4 transformers
- configured in igndualout, that is perfectly valid and correct for a multispark engine like this
- either 4 driving the 4 modules individually (best setup)
- or possibly 2*2 connected in parallel (yes, connecting low-side switches in parallel is also safe).
- Option 3 : using 6 powerIGBT-s, can be wired with two coils each.
- it is double the current but ok if dwell is set sufficiently - not too high
- must have peak RPM < 7000 RPM (in fact only 3500 rpm).
8 powerIGBT (0 logiclevel)
- use stepper-A and Stepper-C outputs with 100 Ohm protection resistors for 2 or 4 external ign-driver modules (4 transformers, 8 sparkplugs),
- and 8 power-IGBT outputs for +8 transformers (+16 sparkplugs)
- igndualout is suitable for this, but it also applies to stepper ignouts, therefore (by actuating/consuming the pair of every selected output) allowing only 2 independent stepper outputs (unless firmware mod is applied)
Wasted spark groups cyls with 360 crankdegrees
On this engine every cylinder head has an inner and outer bank, those will be handled and controlled by the same output signals from the ECU. Each wasted spark coil will send spark to the pair of cylinders that are 360 crankdegrees apart. One coil is _not_ wired to the two plugs belonging to the same cylinder,
Each bank is a regular inline 6 cylinder with 153624 firing order (same as this big V12 is related), the pairs are the usual 1+6, 2+5, 3+4 and will use one Bosch 3x2 coilpack each.