How to wire quad spark grounds with Ford Coil On Plug setup.

[MalcolmV8]

I was reading the quad spark documentation and it says the black grounds coming out of the quad spark go to the cylinder head. However my coils (2003 Mustang Cobra) have two terminals. One for positive and the other for negative (I don't think polarity matters). I'm pretty sure I need to wire each of the individual grounds to the coil grounds rather than to the cylinder head or it wouldn't complete the circuit to the ignition coil. How have others done this?

The factory ECU and setup has a constant 12 volts to one terminal on each of the coils and the ECU grounds the other terminal to fire the coil.

[CRSTune]

Polarity does actually matter on two pin coils. Reversing polarity changes the direction the arc travels.

The coil will have a power wire on one pin and the output of the Quadspark to the other. The Quadspark takes a logic level/5V signal (like the ECU's output) and converts it to a ground output. That is what grounds the coil, commanding it to charge. The factory ECU has the igniter built in.

[juansh2385]

I was reading the quad spark documentation and it says the black grounds coming out of the quad spark go to the cylinder head. However my coils (2003 Mustang Cobra) have two terminals. One for positive and the other for negative (I don't think polarity matters). I'm pretty sure I need to wire each of the individual grounds to the coil grounds rather than to the cylinder head or it wouldn't complete the circuit to the ignition coil. How have others done this?

The factory ECU and setup has a constant 12 volts to one terminal on each of the coils and the ECU grounds the other terminal to fire the coil.

You did not understand the instructions.

The grounds ( installled on the cylinder head) that are specified in the wiring diagram of the quad spark are the grounds source for the igtb inside the quad-spark.

The ground outputs from the quad-spark are the ones that you need to connect to the coil.

and the igtb inputs(5v coil out from the expansion to the quad input) are the ones that saturate the igtb in order to make the switch states to control the dwell time and and timing.

[MalcolmV8]

Thank you that makes much more sense. I had not found a wiring diagram on diyautotune.net but only explanations and obviously misunderstood. I googled for some wiring diagrams and see now how it works.

Follow up question: My quad spark boxes and MS3 will very likely be placed under the passenger's seat. Can I tie the four ground wires together of each quad spark box (I will have two of them) and run a single wire to the rear of a cylinder head? Or do I need to run 8 individual grounds and tie in only at the cylinder head for interference reasons?

Thanks again
Malcolm

[DaveEFI]

I'd mount the QuadSpark unit as close to the coils as possible (perhaps on the bulkhead in a suitable box) to keep the high current wiring as short as possible.

[MalcolmV8]

I'd mount the QuadSpark unit as close to the coils as possible (perhaps on the bulkhead in a suitable box) to keep the high current wiring as short as possible.

If anything I could put them in the passenger's kick panel area where the stock ECU goes and just tap into the factory wiring right there.

[jsmcortina]

There's a diagram in the manual.
http://www.msextra.com/doc/pdf/html/MS3 ... 4-108.html

James

[MalcolmV8]

Thank you.