next question about Fiat COP (3pin) (I guess passive?)

[ZoLtaR]

I mean the COPs from Fiat 1.4 T-Jet engine. Here's some spec.



Looks for me like it's a passive one and must be drived by IGBT high current output.
According to pinout I would connect it this way:

Pin 1 : Connection to engine of engine secondary circut - EC36pin26 (GROUND)
Pin 2 : Primary circuit +12 power supply - Fused +12V for coils
Pin 3 : Control to earth from primary circut - To VEMS High current IGBT outputs.

Is this correct?
Thanks for advice.

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If the resistance between pin 2 & 3 is around 0.3 ohm then it sounds about right

[ZoLtaR]

Thanks again. I will measure this value and let you know about it.
Why, they are using 3rd wire to connect COP with ECU ground cables? Some advantages of such a construction according to "typical" +/- 2pin passive coils?

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When I was fitting a VEMS on a Nissan S13 we decided to see what the ground on the coils actually did, as many say that the ground connection is not needed.
We crimped the grounds to a ring terminal, and held the crimp with a pair of pliers close to the negative battery terminal - about 1cm from the terminal we got a stream of blue sparks, and the engine started to run audiably cleaner.

[ZoLtaR]

Wow, that explains a lot.

Today I measured the coil with DVM. Between 2 and 3 pin there is about 0,8-0,9Ohm impedance.

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Thats going to be your primary coil then, wire it as you suggested.

[mattias]

Why, they are using 3rd wire to connect COP with ECU ground cables?

Definately do not EVER do that. The coils ground pin should be directly wired to the cylinder head.

Some active coils have both a ground like this one, that connects to the head, and sometimes a signal ground to form a signal pair with the actual signal that drives the coil input.

[ZoLtaR]

Thanks Rob. I will wire it up like I wrote before but will ground it to cylinder head as mattias suggested.

Mattias, thanks for your advice. Didn't know this. Should I ground coil ground pin in the same place of cylinder head where VEMS common ground is grounded?

Is there some "typical" dwell time for such a COPs ? 3ms will be ok for them?

[mattias]

No, the VEMS common ground should not be connected at the same spot. I usually put the common ground in the chassis and just make sure the engine is well grounded to it, the generator and starter motor in particular. Some conflicting advice about this in the guide, I know.

I would start out with a 10A fuse and 2 ms dwell for the coils. Up the dwell in case of mis-fire or suspected poor spark, try 3-4 ms to see an improvement. Don't go with a bigger fuse if it blows, think about what you're doing.

[ZoLtaR]

Great. That explains a lot for me. Thanks. I will start with 2ms value and see then what is going on on WOT and 1,5 bar of boost.

About grounding. In fact, comparing with all the guides and manual around, method of grounding the ECU to the chassis is quite controversial  ;)