I started a thread because i have spark blow out issue with cop conversion and just want to go back to coil pack

http://www.modularfords.com/f5/cop-valve-covers-spark-plug-wires-190234/

By doing some search it looks to me like the cop conversion like everyone is doing it in series in the link below does reduce spark energy.TCCoA Forums - View Single Post - why does my car still run with NO spark plug wires hooked up at all??? .



I only have some basic knowledge of electricity so please feel free to chime in and give your toughts and opinion.

Here's what i came up with :

An msd coil pack have a .530 ohm primary resistance .

http://www.livernoismotorsports.com/...ster-Coil.html

So it seems okay to say that a 96-98 ignition module will support that resistance and probably under .530 ohms

A ford cop in good working condition should test between .3 and 1 ohms . Mine all tested around .7ohms. When we put these in series the resistance is now 1.4 ohms . The way everyone run the cop conversion, we have nearly 3 times more resistance than the msd coil pack. I guess that we can say that a cop conversion definetly weaken the spark

Even wired in parallel, the cop will have a .35ohms resistance which is still in the tolerance limit. Wiring the cop in parallel SHOULD increase spark output without frying the ignition module

The internal circuit of the wastespark coil pack is in parallel not serie. The haynes manual say that the primary resistance of a coil pack should be between .3 and 1 ohms. Same thing as the cop. Unless i'm missing smoething the 96-98 ignition module will support the cop in parallel. That's the way the coil pack are '' wired'' normaly. Not in serie.

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I thought about going to COP on my 4.6 but the OE coil packs on there do a damn good job.

 

Sounds reasonable. Would be interested to know if parallel COP works as well as the coil packs.

The parallel DC resistance of two COP coils having .7 ohms each should be closer to .35 ohms. Did you take a reading in the parallel configuration?

 

Yep my mistake should have wroth .35 ohm which is still in the limit of a good working coil pack ( .3 to 1 ohm is ok) If a coil have a .7 ohms primary resistance and we had a .3ohms resistor to it in serie, we now have a primary resistance of 1 ohm. When wired parallel the cop will go down to a .5 ohms primary resistance which is close to the primary resistance of the msd coil pack and would probably make things easier on the ignition module.


For the reading in parallel that's the next step. Like describe above, i could add some resistor to bring the resistance where i want.

 

Yes a resistor will ease the strain on the ignition control circuit, but keep in mind that the resistor will also diminish the power delivered to the coil(s) primary. The power the resistor will absorb in watts is I^2xR (current I squared times resistance R) or V^2/R (voltage drop squared over R). It seems there is a fine line between limiting power to prevent damage to the control circuit, and delivering sufficient power to the parallel coils. Keep us posted.

 

https://www.theturboforums.com/smf/the-modular-forum/spark-blow-out-156876/
https://www.theturboforums.com/smf/the-modular-forum/gm-ls-coils-on-a-mod-motor-using-the-ford-ecu/

 

Here is my plan. With the MSD coil pack having a .530 ohms resistance , i will try to stay as close or above that number. I will have to wire the entire system and check the resistance before adding any resistors to check the added resistance of the wires . I also have a set of weaon X cop wich all tested with 1.3 primary resistance. which would bring the resistance to a more confortable .65ohms

I will keep you guys posted. I will probably start next weekend.

 

I understand what you are saying, but even with a boost a spark it does not work. The increase in voltage will reduce the effects of the increase in resistance from a series set up. One more thing to keep in mind is that testing a coil with an ohm meter will not necessarily give you the true resistance of that coil. You also should not be worried about the resistance but rather the current draw. The current creates heat which is what damages electrical components. Figure out the current draw of the coil pack set up and then monitor the current draw with the cop set up. This would give you much more accurate results.

 

How can you find the real resistance of a coil ? I tought that the amount of resistance will have a direct effect on the amp draw. Voltage / ohms = amp

 

You are correct with your ohms law. But this coil is inducing a field into another coil - taking 12v and stepping it up to 40,000v. The coils never touch each other, the winding wraps are not supposed to be touching each other. The copper wire is coated (even though it looks bare) and can be wrapped hundreds of times around a magnet/iron core. If that winding had a nick in it, you would never be able to pick it up with a meter, (one coil may have 12 ohms, the next coil you test has 12.3 ohms, is that your meter or a failing coil? Kind of like a starter motor winding. You can have a shorted winding, test it with a meter and it appears to be good. (you don't check a starter motor with an ohm meter you check it with an amp meter) Put some current through it and the short appears. So we use amp meters to accurately field check coils, transformers, motors and alternators.

 

How can you find the real resistance of a coil ? I tought that the amount of resistance will have a direct effect on the amp draw. Voltage / ohms = amp
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You actually already measured the DC resistance. What you haven't measured is the coil inductive-reactance, which when combined with the DC resistance gives the total impedance of the coil. The coil inductance will only cause the total impedance to increase above the DC resistance for current that changes over time (has a frequency > 0). Inductor impedance is proportional to the frequency of the applied voltage, so it passes less current than if a steady DC voltage is applied. So the DC resistance is the worst case minimum impedance the ignition circuit will see and therefore the highest current. Point is the coil total impedence wont be less than the DC resistance.

I wouldnt get too concerned about measuring the coil inductance. The coils are already built, the indutance is-what-it-is and you wont be changing it. Not knowing the inductance wont affect your experiment.

 

Honestly him lost . Like i said on my first post i only have basic knowledge of electricity . From what i understand is that worst case is that i will have more impedence than i tought in the system and not damage anything.

 

Sorry, I don't mean to vomit a bunch of electronics jargon on you. I just wanted to give rationale as to why I was telling you that you don't need to know the coil inductance to know the worst-case minimum impedance in the circuit.

I probably should mention "fly-back" which is the result of stored energy in the primary coil immediately after the driver opens the circuit to initiate the spark. The ignition circuit uses a diode to protect the driver by limiting the fly-back voltage and drains the stored current from the coil. So the fly-back voltage and current from the two COPs on each trigger circuit just needs to be within the capacity of the fly-back circuit. It's probably a non-issue but just thought I should mention it.

Carry on.