NON ZR-1 Technical Help needed

[limey]

You guys are smart and i know we have some ECU geniuses here, so i pose my dilemma.

I'm been trying to convert a lamborghini that uses Marelli 3 pin C.O.P. ignition coils to the more common and easy available VW AUDI 4 Pin coils.

For the love of me, i can't get a spark. I switch back to the 3 pin coil and fires right up.

Ive attached 2 pdf pages, the 2002 Murcielago uses Marelli 3 pin, the 2004 uses VW 4 pin coils.

On the 2002 cars, the coil wiring is as follows:

Pin 1 = 12V Power
Pin 2 = Signal Ground
Pin 3 = ECU Signal

On the 2004 cars, the coil wiring is as follows:

Pin 1 = 12V Power
Pin 2 = Signal Ground
Pin 3 = ECU Signal
Pin 4 = Chassis Ground.

So, why when i ground pin 4 on the 2002 retrofit, the car doesn't fire?

[GOLDCYLON]

What happens when you Ground 2 and 4 together or are you running pin 4 to a seperate ground?

[XfireZ51]

Which ECM are you using? And has this retro been done before?

[XfireZ51]

I have a feeling the 4 pin Chassis ground is short circuiting the Signal w the VW coils. Are these coils of equal output?

[limey]

Originally Posted by XfireZ51

I have a feeling the 4 pin Chassis ground is short circuiting the Signal w the VW coils. Are these coils of equal output?

The VW coils read a LOT higher resistance than the stock ones. I was told that i may need an ignition amplifier, but haven't looked into this yet.

[Paul Workman]

Well, right off the bat, the schematic for the Lambo coils leaves a lot of questions. That and exactly what/how the (ECM) signals the coils: beit a ground or??

And, another thing: If I signal trace the VW circuit and go by the schematics provided, either the schematic for one or the other is wrong, or it is a positive ground whereas the Lambo is a negative ground chassis. Do we know that to be the case? Cuz if it is, it makes a big difference how the switching transistor is biased on, and explains why the VW coil will require some faniggling to make it work.

Note: RE the 4 pin coil: The collector of the transistor switch is grounded, and appears to be a NPN (if the diagram is correct). The emitter connects to (I presume) the battery, and to bias the transistor ON, the emitter voltage would have to be to be negative in relation to collector. That would suggest the chassis is a positive ground, assuming the schematic symbology is accurate. Or, am I missing something?

It may be possible to fanigle the VW coils, but to see what is what, a breakout of the Lambo coil is required; that or taking a whack at guessing how it is configured and experimenting. Do you have one of each in hand? (I'm guessing you do.)

[limey]

Originally Posted by GOLDCYLON

What happens when you Ground 2 and 4 together or are you running pin 4 to a seperate ground?

Nothing, same no spark issue

[geezer]

Kurt; Hope you find a solution for this. BTW still waiting for your parts to arrive here. Check your emails.
Thanks; Bill

[limey]

Car is in house and all tests can be confirmed. I have lots of coils :-)

[scottfab]

OK Kurt, Here is what I've found.
To start with the pdf schematics for the 2002 and 2004 are more of a logical diagrams and do not contain all actual specifics of the circuit.

Having said that and after examining both coils I now know enough to say the 2004 circuit uses a positive transition pulse to turn the coil (create HV at the output).
The 2002 circuit uses a negative going pulse to do the same.
An example here shows what the two look like. First is the 2004 pulse
the second is the 2002 pulse.


What does this all mean? It means just changing the wires in the harness and shorting pin 2 to pin 4 will not work.
What has to happen is an inversion of the pulse on each coil input from the ECM.
This can be done by adding a transistor (and possibly other protective components) to each coil. I can furnish a rough schematic of this.
Sorry I know this is not what you were hoping.

BTW the output voltage of the 2004 coil is MUCH greater than the 2002 coils.