Aftermarket Ignition trigger signal compared to OE

[MKhan01]

Hello all,
I have a question regarding the trigger signal output supplied on a coil on plug. The OE has a trigger signal of 2.0 mA and the aftermarket has a trigger signal of 4.2mA. I have not tested the coil on the vehicle(do not have it, only bench testing).

From my understanding the trigger signal basically "triggers" the primary circuit to turn on and off which then leads to the secondary circuit discharging a high voltage. The trigger signal is also generated by the ignitor chip which recives a low voltage from the ECU/PCM.

I have came to a conclusion that the trigger signal is only related to the ignitor chip itself and has no relation to the ECU/PCM except only the input which it recieves from it(5V). There is also a feedback circuit(4 pin COP) which the ECU identifies if the coil fired or not. But I am not working on this type of coil.

My question is, what negative effects can double the trigger signal have on the vehicle and it's electronics? Is my conclusion correct?


Thanks for reading this long post, any help would be greatly apprecirated!

 

[bradrs]

Your conclusion may not be valid. Are you just measuring the coils with a 5V signal to them? You need to put it on the car. Unless you know for certain exactly how the ECU drives the coil, your measurements are only valid on your bench. The ECU may have some sort of current limiting resistor in it, or other limitation on the current to drive the coil driver. If so, trying to drive twice the current could result in a voltage drop on the signal, and the coil not triggering.

And when you say the aftermarket takes twice the current, is that what is required to get it to trigger? Or is that just the current you measured with a 5V signal to it? Did you attempt to trigger it with the same amount of current as the OE? There are a lot of unanswered questions if you are trying to detail out how this works.

I'd put it on the car and look at current and voltage levels for a minute or two, then call it good. The trigger levels, while important, should be the least of your concerns when swapping out coils.

 

[MKhan01]

We have a generic Toyota style ignition driver box which we use to bench test the coils. The output of that box is 5V and I measure the current on the trigger signal wire. They both fire with the same inputs, 14V to the primary and 5V to the trigger circuit.

The coils both fire and I get similar values but my main concern is the scope trace of the trigger signal. The aftermarket is more than twice the OE's scope trace with the same inputs.

Unfortunately I am looking for a vehicle to test it on but, no luck.

 

[bradrs]

I'd test to see if there is a valid range of voltages/currents required to drive these alternate coils, and how they stock up to the OEM. You don't want to get it too close to the edge of running, or any sort of little voltage loss in the wiring could cause problems.

But back to your main question, the negative effects on the vehicles electronics. The few mA should not appreciably affect the ECM. But measuring the change in voltage output with the extra current load will give you a better idea of what the ECM can handle.

I'd worry more about the other aspects of the coil. Is the dwell time for this coil matched up well to the dwell time the ECM provides for the stock coil? It's pretty easy to get a mismatch that either overcurrents and cooks the coil at low RPMs, or provides inadequate charging at higher RPM.