Hey Joe---and other electric/electronic gurus

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cammerfe

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I'm in process of planning improvements---that'll likely actually start when the weather clears. One of the changes I have planned is the removal of the factory-style COPs-(They're actually Accel Mustang items)-and the substitution of the style that're used in the 'chibberlay' V8s.

I'll therefore go to a lay-out that includes a mounting rail to hold the coils, mounted to the cam cover, and a 'pig-tail' short coil wire including an aftermarket plug boot such as is designed for sealing the plug tubes in such as the venerable 'Hemi'.

I'll have to find a source for the plastic 'plug-in' connectors to match the coils.

Any input as to the suitability of such coils---chosen due to capacity available from the physically larger units---would be much appreciated.

TIA

KS
 
I don't have any specific input. I will say that the LS PCM seems to be susceptible to damage from coils. I'm not willing to make any bets on if it will be able to handle coils it wasn't designed for.
 
It's my understanding that the interface between the coil and the PCM is such that the coil is 'fired' by switching the ground. If I understand correctly, the 'hot side' is a constant and the ground goes through the PCM, which turns it on and off. If that's true, I don't see any reason that the circuit design wouldn't work on any 12 volt negative ground automotive coil.

I'll take this up with the tech guys at the aftermarket company. I'm, at this point, simply trying to learn enough so as to be able to act as if I sorta know what I'm talking about.

Thanks Joe, for your input, as always. And please, to everybody else, feel free to jump in with questions and comments.

KS
 
Yes, the PCM switches ground on and off to the coil. All the current the flows through the primary of the coil has to flow through the transistor in the PCM. Coil current is mostly a factor of the inductance of the coils. They don't generally publish the inductance of the coils, since only the PCM designer and coil designer really need to know that. This will make figuring out if the new coils are going to overload the PCM very difficult. There's also the problem of the voltage spike on the primary side when the coil is switched off. There are diodes and other measures in the PCM to protect against this, but they were designed for the OEM coils and may or may not handle the coils you have in mind.
 
I would imaging there would be a way to measure the voltage, current and other items that it is currently emitting (withstanding) then place a fuse in the positive wire near the coil to protect the PCM in the testing stages if you are unable to confirm from the manufacturer if it will be okay.

I have been thinking about the chevy coils for the LS motors as well recently as they are more durable, and perhaps more powerful as well.

I would imagine with a Digital Volt Meter in the positive line you could monitor for voltage spikes and see how high they get if it all through the RPM range.

I think you should be able to find someone on a chevy forum that would be able to give you tons of insight into the chevy coils themselves. They may not spike at all based on their design.
 
Yes, it can be measured. However, a voltmeter would never react quickly enough. A good oscilloscope would be required.
Unfortunately, fuses for protection would not work. The current pulses are simply too fast for a fuse to react to before damage was done.
As for the GM coils and spikes, it's a system level thing. What they do in the GM system may not be the same as what they'll do in the LS system. BTW, coils are specifically designed to create voltage spikes, that's how they fire the plugs. Of course, most of that is supposed to be on the secondary side, but it's almost unavoidable that some will be on the primary side.

All that said, it may all be fine. The point is that I can't promise it. Someone will just have to try it. They should just know that they may be putting their PCM at risk.
 
Our coils are "dumb" as the igniter is remote from the coil. GM LS engine series coils are "smart" as they have a built in igniter. Our vehicle pcm just dumps the current into the primary coil. Chevy coil needs a logic level signal (0-5V) to let the built-in ignitor know when to start charging the coil. Our PCMs may also measure the coil input current and voltage and use the information for misfire calculation and with GM coils that wouldn't be possible.

There are many sources of information about the Chevy LS series coils. Motec's web site is a treasure trove of information regarding engine sensors and controls. Also, you may visit megasquirt and microsquirt forums and find information regarding hardware differences when using "dumb" and "smart" coils.

Pigtail connectors can be bought from GM or Motec usa. GM LS 1 and 2 generation coils have different pigtails.

Good luck with the project.
 
Thanks for the info! Is it your supposition that the presence of the igniter is an impediment to use such as I've proposed?

KS
 
If this is the case, then the use of a Vortec coil from a 96-98 model Chevy truck might be the answer. The coils used on those trucks are dumb coils, and are triggered by a simple signal from the ignition control module. These coils can be had for about 40 bucks each, and usually last over 100K miles firing all plugs. 8 of them firing once per cylinder would likely last a million miles.
 
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