Ignition system

 The M60 and M62 V8s use eight Coil-On-Plug (COP) devices to fire the spark plugs :

If you find a way of retaining the BMW ECU and loom then you can leave these be.

But if you're using a programmable ECU then you may have problems finding an affordable one that will run all eight coils. Generally, the more expensive the ECU is, the more coils it can run. 

Alternatively the COPs will need replacing with coil-packs for a wasted spark system. Which allows all eight spark plugs to be driven by four ignition drivers.

The commonest coil-packs available in the UK are those from ford escorts/mondeos and similar 4-cylinder cars from the '90s. These units consist of two coils, each coil firing 2 cylinders at 180 degree intervals. This is known as a wasted-spark system as the plug will fire at the end of the exhaust stroke as well as at the top of the compression stroke. Using two of these coil packs you can fire all 8 plugs from 4 ignition signals. Mine are 2 Mondeo units.

You could either use an ECU with four ignition outputs to drive the coilpacks directly or use an ignition module, which is what i decided to do. This is an encapsulation of transistors and microchips that will sort out the firing order of the plugs rather like a distributer (but without any moving parts) All it requires is a speed signal from the crank sensor, power, and a signal from the ECU to tell it how much ignition advance to run at various speeds/loads. The ECU then takes the inputs/outputs from the ignition module similarly to how it would be connected to a distributer.

There are several different ignition modules of this type for four and six cylinder cars (Bosch 211, GM DIS, and the Ford EDIS). But the only commonly available 8 cylinder ignition module is the Ford EDIS-8 system, used on various yank-tanks for many years. This is available from www.Trigger-Wheels.com or they can be picked up on Ebay from the States. The wiring diagrams for these are quite simple and are on the Megasquirt website.

The only hitch with them is that being Ford, they require a 36-1 trigger wheel (36 teeth, 1 missing) whereas the BMW uses a 60-2 trigger wheel.  Which means machining-off the the BMW wheel, and carefully welding on a new 36-1 wheel. These are also available from trigger-wheels.com in various sizes. The original BMW crank sensor was retained but moved to a new position to suit the smaller diameter of the new trigger wheel. If you were driving the coilpacks direct from an ECU with 4 ignition outputs then you could avoid all this and retain the BMW's 60-2 trigger wheel.

In hindsight i could have got an ECU with 4 ignition outputs, which would have avoided the hassle of fitting the EDIS-8 ignition unit and changing the trigger wheel, but i didn't know this at the time. Since i started this engine conversion it seems like 4 ignition channels has become the standard for a lot of mid-range ECUs.

With a more professional ECU like the DTA S80 you get 8 ignition outputs, sequential injection and a lot of extra channels for traction control and boost control, but it's not a budget system.

The amount of technology that comes as standard in the original Bosch DME ECU is quite amazing, so there's certainly a strong case for trying to keep the original ECU if you can get around the immobiliser. It depends a lot on whether you want to adjust the engine fuelling and spark to cater for performance modifications or whether you just want it to run stock.

Wasted spark ignition isn't that inferior to COPs but for modern manufacturers it doesn't give them enough control over emmisions or trimming individual cylinder ignition, but it's still a huge leap forward from mechanical distributers. I suspect that in a couple of years the technology and knowledge will advance and everybody will be running COPs from budget ECU systems on V8s, but at the moment it seems a bit like voodoo for the unninitiated.

For Megasquirt systems some gurus have built special sequencer boxes with their own circuitry and ignition drivers for running multiple COPs. But when i try to read circuit board schematics and details on resistors, JFETs and diodes my mind slowly goes blank and my vision glazes over like i'm being hypnotised. I'm working to overcome this...

I'm guessing that the Bosch COPs on the M60 don't have inbuilt ignitors because they only have 3 wires and the third wire is a shunt circuit to monitor the high tension discharge (to tell the ECU if ignition has taken place in the cylinder).  The latest MS3 Megasquirt system has an add-on MS3X sequencer board that can provide 8 logic-level outputs which could then fire eight LS1/LS2 coils or similar COP/CNP with inbuilt ignitor and known specifications. 

EDIS-8 Ignition module and coil packs  :

Universal 36-1 trigger wheel just large enough to go over the rear of the pulley diameter when machined  (i can't remember if this was the 6.5" or the 7.25" outer diameter without measuring it again) :

New 36-1 trigger wheel on the crank pulley :