Wasted Spark Question

[badjuju]

I'm thinking about running a 36-1 wheel, a daughtercard (for the vr conditioning circuit), and 3 coil packs for spark. This would only work, however, if the pistons were at tdc in pairs. ie, are pistons 1 and 4 at tdc at the same time? (given, these would not be on the same strokes)

[mobythevan]

You can do it easier than that by just running one 6 post coil and it fires at every TDC. If that is what you want. Be sure to read the thread by braap about EDIS.

 

Look in the must read sticky for the link

[badjuju]

I'll read up on it, but my buddy is doing the same setup on his volvo, and he bought a set of 7 coils, meaning his 4 cylinder volvo engine will leave 3 left, which i could buy from him for cheap. is it possible to do it this way?

[Clifton]

That's what I'm going to run on my 7M. It already has a waste spark set up. You can run it with the EDIS module.

[badjuju]

My friend tells me that with a vr sensor for edis you need a conditioning circuit. can someone explain how this works to me, and why you need it? is it anything like the +5v from the tps that is common on the CAS installs?

[Clifton]

On MSII you don't. I don't know about the other MS's. http://www.megasquirt.info/ms2/EDIS.htm

[z-ya]

If you are using a 36-1 wheel, then just use an EDIS module and the EDIS code for MS. It does all the conditioning required.

 

You want to fire 1&6, 2&5, and 3&4 together. The EDIS and Chrysler coil packs are setup for wasted spark 6 cylinder applications. Four wires, one for +12V, and then one for each coil tower pair (each coil). The EDIS-6 module provides three coil low side outputs that drive the coils directy. It's pretty easy to hook up.

[badjuju]

Z-ya, could you draw up a diagram of this for me?

[z-ya]

Hear is the diagram from the MS EDIS information page:

 

 

This is basically all you need to know.

 

The coil ouputs (pins 10, 11 and 12 on the midule), should go to the following minus terminals on the three coils. Not that if you are using an EDIS-6 or Chrysler coil pack, there are three coils in one module.

 

 

Pin 10 goes to minus terminal of coil driving cylinders #1 and #6

Pin 12 goes to minus terminal of coil driving cylinders #2 and #5

Pin 11 goes to minus terminal of coil driving cylinders #3 and #4

 

So the coil A output should go to the #1 and opposed (#6) cylinders

 

I will be testing this out over the next week, so I will update this post if I find anything wrong.

[badjuju]

Have you tested this stuff further, and if so, has anything failed?

[badjuju]

Can you also elaborate on the workings of pin 4 of the ignition coil harness? it looks to me like 12v comes from a relay and is grounded out, but also connects to pin 4.

... doesn't seem right to me, i think i'm missing something really important.

[Clifton]

Have you tested this stuff further, and if so, has anything failed?

 

It's stock Ford stuff, been tested on half of there cars, trucks and mini vans for 10 or so years:wink:.

[z-ya]

I have the engine running now, but have not got the advance to work yet. It's running in limp home mode with a fixed 10deg advance. I'm getting some noise on the SAW signal that comes from the MS and tell the EDIS module what the advance should be. I need to shield the SAW signal better.I hope to get that fixed today.

 

I updated the wiring in my post above. It is now correct.

 

I'll update the post when I get the advance working.

[badjuju]

It still looks to me like i'm grounding a 12v power source at ign coil #4... can someone elaborate on this, on how i might be reading it wrong?

[woldson]

the 25 uf is a rf ground, it grounds rf not power, that the stuff that grounds the noise that can cause you problems.

[badjuju]

So what do I do to ground it? What do I put between the power wire and the ground?

[z-ya]

There is a RF suppression capacitor that you should use, but it is not required. If you have a stereo in your Z, you might want to add one. It is basically a 25uF capacitor that connects between the +12V to the coil, and the chassis. The Chrysler coil packs come with one attached to the harness, so if use one of those coils, take the capacitor with it.

 

Just so you know, a capacitor cannot pass DC current, so to the battery, it looks like an open circuit. To AC signals like RF frequencies, it acts as a resistor, which attenuates (reduces) these signals. It acts as a radio noise reducer in this application.

[badjuju]

alrighty, thanks a bunch!