Poor Mans HEI

[Canoe]

Heat sink.
If the plate you mount on can have more contact with the box, then the box and the inner fender it's bolted to become part of your heatsink capacity. The mounting plate could be slightly larger and then sandwiched between the stock box and it's bolt down points.

First wire-in of these I've seen that required a diode. Is this due to using the stock harness instead of the usual direct wire method?

As both the MSD coil and this Ignition Module can handle full voltage, does this wiring setup bypass the startup ballast resistor so your coil is running at full potential all of the time instead of only at startup?

Is this working with the stock ECM electronics setup or have you done the ECM By pass Test?



From notes gathered previously, Ignition Module for:
"'78 Camaro with a 350" or "1980 Camaro 3.8L"
AC Delco D1906
Wells DR100
Car Quest #21040
Napa: Echlin ECHTP45 or Mileage Plus #MPETP45SB
Niehof DR400
Standard LX301
(with a note to avoid Parts Master LX-301 - high failure rate reported)

[shaggimo]

Heat sink.
If the plate you mount on can have more contact with the box, then the box and the inner fender it's bolted to become part of your heatsink capacity. The mounting plate could be slightly larger and then sandwiched between the stock box and it's bolt down points.

First wire-in of these I've seen that required a diode. Is this due to using the stock harness instead of the usual direct wire method?

As both the MSD coil and this Ignition Module can handle full voltage, does this wiring setup bypass the startup ballast resistor so your coil is running at full potential all of the time instead of only at startup?

Is this working with the stock ECM electronics setup or have you done the ECM By pass Test?

On the diode, could be, I found a decent write up on it that stated to put it in there, so I followed their directions (I suppose it's there to prevent run-on, similar to what one has to do to put msd in a GM).

The start up resistor wire was controlled by the motorcraft ignition module, so yes coil and module get a full 12 volt zap.

The eagle I did this too, was an 81, so it had no ecm. In order to run this you would have had to do the nu-tt-er bypass.

[ammachine390]

In order to run this you would have had to do the nu-tt-er bypass.

Are you sure? The stock motorcraft ICM was made to be used the way you hooked up your HEI, but AMC made it work with the ECM. I would think that if you hooked up the appropriate wires from the wiring harness to the HEI module, it would still work with the ECM in the loop. The only difference would be that you would only have to hook up 3 wires to the HEI module for 83 and up models instead of 4 that you had to do for your 81.

However, you wouldn't be able to keep the ECM in loop (at least for timing control) for 82 models though as the MC ICM had a 3rd connector for the timing control, which an HEI module does not have.

[shaggimo]

Now you got me wondering if it would work with keeping the ecm in loop. Good point. I don't have vehicle to guinea pig that on, the 84 I have, has already been tampered with. Actually.......I may be doing some work on a bone stock 84 or 85 in the next few weeks, maybe I'll grab the module out of the sx/4 and see if it runs the other car with no issues, clear that up a little bit, lol.

[Canoe]

The start up resistor wire was controlled by the motorcraft ignition module, so yes coil and module get a full 12 volt zap.

How?
If you're using the stock wiring harness (it appears you are), then the coil gets full VDC when the ignition is starting, but is in series with the ballast resistor while running and does not get full VDC.
One of the main benefits of the GM-HEI IM with a TFI coil is you can bypass the ballast resistor to get full voltage to the coil all of the time. I don't see how swapping the stock IM for the GM-HEI IM using the stock connectors achieves this.

[shaggimo]

Well, I'll do a retest at home tonight with my volt meter with the ignition on "run" position, and see what I have. Im pretty sure I have a full zap to the coil in run position, I beleive I tested it back when I did this to the car because the same question arised, but that was over two years ago, lol, so we shall see....stay tuned 

[shaggimo]

As promised, I went out and checked the sx last night.


this is my volt meter hooked up to the battery, just to show it is accurate, and not giving false readings.


Here it is hooked to the positive terminal of the coil with the ignition in the run position. I did nothing to the cars' wiring, with the exception of spade terminals at the coil vs the oem horse shoe.

I didn't think of this til this morning, but I should have plugged the factory module back in and took a reading, oh well, maybe if it stops raining long enough I'll do that tonight for comparison sake.

[Canoe]

(Sorry I haven't got back for so long.)

If you (and prior owners) did nothing to the wiring, and did not remove or bypass the ballast resistor, then when the engine is running, the ballast resistor is in series with the coil (as shown in the wiring diagram).

This is why the write-ups that used to be around on this IM upgrade specify that to get the max from a TFI coil you can/should bypass/remove the ballast resistor.
(I have a vague recollection that bypassing the ballast resistor with the stock coil is not a good idea, no recollection why, but I'm not sure I trust my memory on that - it's late).

You can see the 0.2 VDC voltage drop between the two photos. But this doesn't mean much, because part of that voltage drop should be due to the load on the battery when you turn the ignition on.

With the ignition on, using the same ground point, you'd need to measure:
* the positive terminal of the battery, and then
* the positive voltage of the coil.
That at least will show you how much drop you're getting from the ballast resistor (and the wiring to the coil). But, this doesn't show what thpse values will be when running, as you should be seeing something in the order of 13.8 VDC supplied from the alternator (providing the accessories aren't pulling it down from too much current draw (I got the 94 amp one, nice)).

If you got that measurement, then that percentage drop should be around the same percentage drop of the maximum coil output.

Except, that's a static measurement, not a dynamic measurement.
There's something about the voltage reduction from the ballast resistor has more effect than expected. Something to do with the rise time of coil voltage becoming a factor as the rpm increases above idle, with a scope required to see the coil output degraded with the ballast resistor in series with the coil. I recall seeing scope photos that showed both a voltage decrease and a change in spark duration (decrease?).

In any event, bypass the ballast resistor and see how much improvement you get.
The jeep forums where this upgrade originated from claimed it was required to get the full bang from the TFI upgrade.
Those that bypassed the ballast resistor claimed they saw an improvement.
YRMV, but (prerequisite: this IM and a TFI coil) bypassing the ballast resistor is a really cheap upgrade.



p.s. found an article where they're putting this IM on Ford Probes, while keeping the ECM triggering it.
Instructions given are:
The ECU's trigger output wire (BL/O) feeds the HEI's pin 'G'.
Ground the HEI's pin 'W'.
Ground the HEI's base.
HEI's pin 'B' taps into the +12V dizzy feed wire (BK/P).
HEI's pin 'C' taps into the coil's primary wire (Y/G).

Claim is that their ECM is Negative Edge triggering, so no problem.
 
Also within the same collection of threads is a warning about failing Niehof DR400 version from Crappy Tire in Canada (but from five, six, years ago).