Motronic COP extension?

[HairyScreech]

one for the electronics and ecu gurus out there, would it be possible to make a coil on plug extension for the motronic system?

the ecu is currently capable of firing 1 coil by switching its earth, and has control of the timing with the distributor picking which cylinder is fired.

thus it has a switched earth that pulses 6 times per firing cycle.

so would it be possible to make a daughter board that could pick up on the coil pulses and then take a cam or crank sensor input and distribute the earthing pulse to the correct coil?

thus allowing coil on plug for the motronic system.

just thinking aloud.

[GeoffBob]

Yes, this is quite do-able. You will however need to retro-fit either an inductive or optical pick-up to your distributor in order to direct the single "common collector" output (that's what it's actually called) from the Motronic to whichever coil is to be fired. I guess that you could (in principle) use the distributor rotor to form some form of crude mechanical switch in order to direct the motronic output to which coil you want to fire, but I have never seen this done, and I suspect that it would be unreliable. Rotors and distributor caps are really only any good for routing the HT (high tension) generated by a single coil to individual plugs.

One way that I believe would be both functional and reliable, would be to fit six optical sensors around the inside of a modified distributor cap. When the rotor tip interrupts the beam from the LED to the opto-transistor it will indicate which plug needs to be fired, but you would still use the output from the Motronic to time the firing of the actual coil. Since the accuracy of timing is down to the output from the Motronic, the "routing" signals from the optical sensors need not be that accurate. In other words, they only indicate which plug to fire, not when to fire it. Optical sensors are commonly available and take the form of a little plastic ”aU”a with an LED on one side, and a light sensitive transistor (switch) on the other. As the rotor tip swings through the ”aU”a it will interrupt the light beam, providing and indication as to which coil to fire. This sounds like a lot of PT to me though, and could turn out very Heath Robinson if not careful. You would have to mill a distributor cap to get this right. TBH, I can’t see the point to all the effort and expense.

A more professional procedure for doing what you want, would be to fit a six-pole optical or inductive (magnetic) pick-up around the shaft at the base of the distributor, and then use the output from the pick-up to decide which coil needs to be fired. These are available commercially I believe, and there are companies that specialise in this sort of work. The distributor cap is then replaced with a blanking plate. I can’t imagine that this would be cheap though.

Whichever route you followed, however, the six outputs from the newly installed sensor in the distributor will be both low voltage and low current, and cannot be used to fire the coils directly. To make your 6-coil ignition system work you will need to purchase six ignitor circuits or a six-channel CDI (capacitive discharge ignition). I'd only recommend the CDI if you are running forced induction or very high compression ratio, otherwise six little "ignitors" will be cheaper and no less effective than a CDI. You'll then need to combine the output of the Motronic with the six ”arouting”a signals to the trigger inputs on the six ignitor circuits, which then, in turn, connect to the six coils.

I can provide detailed info on how to do this conversion if you decide to go ahead, but TBH, it’s more PT and money than getting rid of the distributor is worth. The quickest and cheapest route to what you want is to install an aftermarket ECU which already has multiple ignition outputs. Tim_Haynes, for example, has a Gotech-Pro on his supercharged M20B25 with a 6-channel CDI that I built for him (see here) that fires six pencil-coils (COP), but you could use any ECU of your choice with a set of ignitors.

HTH
Geoff

[Gunni]

It´s pretty simple.

just fit a M50 non vanos loom, ecu and system on to your M20.

;)

It can run without camsync and still provide very good running, tuning can be done by emulator from there on.

[DmcL]

It´s pretty simple.

just fit a M50 non vanos loom, ecu and system on to your M20.

;)

It can run without camsync and still provide very good running, tuning can be done by emulator from there on.

x2

this is one thing id love to try at some stage. would also mean being able to ditch the stock M20 AFM for the M50's MAF without having to fart around in the code/AFM maps in the stock M20 motronic and build a loom, etc. for it.

[fowler]

sounds like too much hassle just use a .............. the kit is available for ditch of AFM for MAF is already availalbe its not that costly
if you want COP. keep it with the required engine and throw a M50 in it as it will be more fun in the long run.
but each to their own just adding my 2penith worth

[HairyScreech]

an informed 2p worth is always appreciated and an m5x engine will probably be on the cards eventually but for now the m20 gets the love, after all there not bad engines, and there a lot more to be had out of them.
once iv finished the 2.8 project the the only logical step from there is m5x though.....

as for COP the intention is to get rid of the distributor as having done a belt change yesterday the rotor was quite bunt, now im sure this has been the cause of my high consumption and poor low speed running for the last 5-6k, as literally everything else was replaced at rebuild and having sorted the burn rotor all symptoms have disappeared.

add a maf for the throttle response that a newer engine design has over the m20 and i dont see much of a reason for most people to move away from the "correct" engine for an e30.

think im going to look into some non-vanos m50 management for the 2.8.

[CHR1S1990]

think im going to look into some non-vanos m50 management for the 2.8.

please let us know how you get on with this

[HairyScreech]

anything i work out will go in the m20b28 developments thread.

iv got the wds so i might start looking into it later.

safe to say with the rotor sorted out the cars much happier.

perhaps hiding a wasted spark coil behind the dizzy cover would be the way to go?

[carannc]

I use megasquirt fitted in a Motronic case and a wasted spark unit off a Omega V6, cheap as chips and you can ditch the distributor and AFM. The wasted spark unit is a little large so its hard to hide but thats the only downside.